TY - JOUR A1 - Schmidt, Bernd A1 - Nave, Stefan T1 - Stereoselective syntheses of enantiomerically pure 2,5-disubstituted dihydropyrans based on olefin metathesis JF - The journal of organic chemistry N2 - A short synthesis of 2,5-disubstituted dihydropyrans starting from D-mannitol as a chiral building block is described. Our synthetic approach combines ruthenium-catalyzed ring closing olefin metathesis and palladium-catalyzed nucleophilic substitution. Y1 - 2006 U6 - https://doi.org/10.1021/jo061190k SN - 0022-3263 VL - 71 IS - 19 SP - 7364 EP - 7369 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd T1 - Olefin metathesis and isomerization : from undesired side reactions to useful synthetic methodology N2 - Conversion of ruthenium carbene complexes to ruthenium hydride complexes by organometallic transformations in situ opens up interesting synthetic perspectives. In this account the use of Grubbs' catalyst to synthesize pent-4- enals selectively from diallyl- and allyl homoallyl ethers and scope and limitations of a Tandem RCM-isomerization sequence for the synthesis of cyclic enol ethers are discussed. (c) 2006 Elsevier B.V. All rights reserved Y1 - 2006 UR - http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGM-4JT9C6D- 2&_user=1584062&_coverDate=07%2F19%2F2006&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_sea rchStr U6 - https://doi.org/10.1016/j.molcata.2006.03.026 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Nave, Stefan T1 - Control of ring size selectivity by substrate directable RCM N2 - Hydroxy groups may exert strong catalyst-directing effects in olefin metathesis reactions, which are exploited for a ring size-selective RCM reaction Y1 - 2006 UR - http://pubs.rsc.org/en/content/articlehtml/2006/cc/b604359c U6 - https://doi.org/10.1039/B604359c ER - TY - JOUR A1 - Schmidt, Bernd A1 - Nave, Stefan T1 - Palladium-catalyzed O-allylation of alpha-hydroxy carbonyl compounds N2 - alpha-Hydroxy carbonyl compounds undergo smooth O-allylation using allylic carbonates and Pd(0) catalysts. This method has significant advantages over other O-allylation methods as it provides a solution to several problems previously observed for this synthetic transformation Y1 - 2006 UR - http://onlinelibrary.wiley.com/doi/10.1002/adsc.200505361/pdf U6 - https://doi.org/10.1002/adsc.200505361 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Staude, Lucia T1 - Unexpected transfer hydrogenation of C-C-double bonds during Tandem-RCM-isomerization reactions JF - Journal of organometallic chemistry N2 - Unexpected hydrogen transfer from 2-propanol to C-C-double bonds has been observed in the course of a Tandem RCM-isomerization reaction leading to sterically congested spirocycles. KW - ruthenium KW - metathesis KW - isomerization KW - hydrogenation KW - transferhydrogenation KW - tandem sequence Y1 - 2006 U6 - https://doi.org/10.1016/j.jorganchem.2006.07.011 SN - 0022-328X VL - 691 IS - 24-25 SP - 5218 EP - 5221 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hermanns, Jolanda T1 - Ring closing metathesis of substrates containing more than two C-C-double bonds : rapid access to functionalized heterocycles N2 - In most cases where ring closing metathesis is applied to the synthesis of heterocycles, alpha,omega-dienes are used as precursors. If substrates containing more than two double bonds are subjected to a metathesis reaction, carba- or heterocycles bearing additional exocyclic alkene functionality result, or multiple ring closing processes occur. This offers interesting and potentially very useful synthetic perspectives. On the other hand, selectivity problems need to be addressed as the cyclization of substrates with more than two double bonds available for olefin metathesis may result in constitutional isomers or stereoisomers. This review highlights problems and opportunities evolving from ring closing metathesis of tri-, tetra-, and polyenes as a strategy for the selective synthesis of functionalized heterocycles. The chapter on RCM of trienes is subdivided according to the symmetry of the metathesis precursor. The following two chapters deal with the double or multiple RCM of tetra- or polyenes. These processes are further classified according to the preferred cyclization mode. Finally, the application of cascade or domino metathesis reactions to the synthesis of heterocycles will be discussed. These processes can be classified into those where exclusively C-C-double bonds take part in the metathesis reaction, and those where one or more C-C-triple bonds are involved Y1 - 2006 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Staude, Lucia T1 - Ring-size-selective enyne metathesis as a tool for desymmetrization of an enantiopure C-2-symmetric building block N2 - The enantiomerically pure C-2-syrnmetrical hexa-1,5-diene-3,4-diol is selectively monopropargylated. The products undergo ring-closing enyne metathesis to give exclusively dihydropyrans as single stereoisomers. An unprotected hydroxy group is identified as the factor controlling the ring-size selectivity. Y1 - 2009 UR - http://pubs.acs.org/journal/joceah U6 - https://doi.org/10.1021/Jo9018649 SN - 0022-3263 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hoelter, Frank T1 - A stereodivergent synthesis of all stereoisomers of centrolobine : control of selectivity by a protecting-group manipulation N2 - All stereoisomers of the natural product centrolobine are selectively synthesized, by starting from a common precursor. Key steps are an enantioselective allylation with enantiomerically pure allylsilanes, a tandem ring-closing metathesis-isomerization reaction, and a Heck reaction by using an arene diazonium salt. By choosing appropriate conditions for the final deprotection step, either the cis-configured centrolobines or their epimers are selectively obtained. Y1 - 2009 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/26293/ U6 - https://doi.org/10.1002/chem.200902053 SN - 0947-6539 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Werner, Frank A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride : formation and crystal structure analysis of an unexpected bicyclic product N2 - 3,4-Dihydro-2-H-pyran and oxalyl chloride react, depending on the conditions, to keto esters, a pyran-3- carboxylic acid or derivatives thereof, or to an hitherto unknown bicyclic acetal containing a vinyl chloride moiety. The structure of the latter product has been unambiguously elucidated by single-crystal X-ray structure analysis. A mechanism for its formation is proposed. Y1 - 2010 UR - 1960 = dx.doi.org/10.1002/jhet.456 SN - 0022-152X ER - TY - JOUR A1 - Schmidt, Bernd A1 - Berger, René A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - Pd-Catalyzed [2+2+1] coupling of alkynes and arenes phenol diazonium salts as mechanistic trapdoors JF - Chemistry - a European journal N2 - Alkynes and phenol diazonium salts undergo a Pd-catalyzed [2+2+1] cyclization reaction to spiro[4,5]decatetraene-7-ones. This structure was confirmed for one example by X-ray single-crystal structure analysis. The reaction is believed to proceed through oxidative addition of the phenol diazonium cation to Pd(0), subsequent insertion of two alkynes, followed by irreversible spirocyclization. KW - alkynes KW - diazo compounds KW - palladium KW - phenols KW - spirocycles Y1 - 2011 U6 - https://doi.org/10.1002/chem.201100609 SN - 0947-6539 VL - 17 IS - 25 SP - 7032 EP - 7040 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hölter, Frank A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - Pd-Catalyzed arylation reactions with phenol diazonium salts application in the synthesis of diarylheptanoids JF - The journal of organic chemistry N2 - The first total synthesis of the natural product (3S,7R)-5,6-dehydro-de-O-methyl centrolobine and various analogues is reported, using a highly regio- and diastereoselective Mizoroki-Heck reaction of phenol diazonium salts and enantiopure dihydropyrans. The assigned relative configuration was confirmed by single-crystal X-ray structure analysis, but a revision of the absolute configuration is proposed based on polarimetric measurement. Y1 - 2011 U6 - https://doi.org/10.1021/jo2002787 SN - 0022-3263 SN - 1520-6904 VL - 76 IS - 9 SP - 3357 EP - 3365 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Geissler, Diana T1 - Olefin-Metathesis-Based Synthesis of Furans by an RCM/Deprotonation/Phosphorylation Sequence and Their Diels-Alder Reactions JF - European journal of organic chemistry N2 - Butenolides, obtained by ring-closing metathesis (RCM) of acrylates, undergo quantitative deprotonation with amide bases. Trapping of the resulting anions with electrophiles, for example, chlorophosphates, give furans. Subsequent DielsAlder reaction and acid-catalysed rearrangement of the resulting oxabicyclonorbornadienes give substituted benzenes. KW - Lactones KW - Metathesis KW - Ruthenium KW - Oxygen heterocycles KW - Metalation Y1 - 2011 U6 - https://doi.org/10.1002/ejoc.201101078 SN - 1434-193X IS - 35 SP - 7140 EP - 7147 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Staude, Lucia T1 - Desymmetrization of (R,R)-Hexa-1,5-diene-3,4-diol via Monofunctionallization and Rhodium-Catalyzed Allylic Substitution JF - The journal of organic chemistry N2 - A sequence of selective monoprotection and Rh-catalyzed enantioconservative allylic subEtitution is established as a desymmetrization strategy for C-2-symmetric hexa-1,5-diene-3,4-diol. A benzyl protecting group and ethyl carbonate as a leaving group emerged as the most useful combination with respect to reproducibility, stereoselectivity, and yield: A remarkable deviation from the normally observed regiospecificity of Rh-catalyzed allylic alkylations was observed for unprotected carbonates. In this case, a linear, rather than a branched alkylation product was obtained exclusively. Y1 - 2011 U6 - https://doi.org/10.1021/jo2001337 SN - 0022-3263 VL - 76 IS - 7 SP - 2220 EP - 2226 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Reznichenko, Alexander L. A1 - Emge, Thomas J. A1 - Audoersch, Stephan A1 - Klauber, Eric G. A1 - Hultzsch, Kai C. A1 - Schmidt, Bernd T1 - Group 5 metal binaphtholate complexes for catalytic asymmetric hydroaminoalkylation and hydroamination/cyclization JF - Organometallics N2 - 3,3'-Silylated binaphtholate tantalum and niobium complexes were shown to be efficient catalysts for the asymmetric hydroaminoalkylation of N-methylaniline derivatives and N-benzylmethylamine with simple alkenes in enantioselectivities of up to 80% ee. No hydroaminoalkylation was observed with aminoalkenes; rather, exclusive asymmetric hydroamination/cyclization took place in up to 81% ee. Y1 - 2011 U6 - https://doi.org/10.1021/om1011006 SN - 0276-7333 VL - 30 IS - 5 SP - 921 EP - 924 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Geissler, Diana T1 - Ru- and Pd-Catalysed Synthesis of 2-Arylfurans by One-Flask Heck Arylation/Oxidation JF - European journal of organic chemistry N2 - 2,5-Disubstituted furans were synthesized by one-flask Heck arylation/oxidation sequences. The starting materials are 2-substituted 2,3-dihydrofurans, conveniently available by RCM/isomerization sequences, and arenediazonium salts. These react in ligand-free Heck reactions to afford 2,5-disub-stituted 2,5-dihydrofurans, which are oxidized to the corresponding furans without isolation or intermediate workup. The oxidation is conveniently achieved with chloranil or DDQ, depending on the substrate. KW - Diazonium salts KW - Palladium KW - C-C coupling KW - Heck coupling KW - Furans KW - Oxidation KW - Oxygen heterocycles Y1 - 2011 U6 - https://doi.org/10.1002/ejoc.201100549 SN - 1434-193X IS - 25 SP - 4814 EP - 4822 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Staude, Lucia A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - A Cross-Metathesis-Conjugate addition route to enantiopure gamma-Butyrolactams and gamma-Lactones from a C-2-Symmetric Precursor JF - European journal of organic chemistry N2 - A protected derivative of (3R, 4R)-hexa-1,5-diene-3,4-diol, a conveniently accessible C-2-symmetric building block, undergoes single or double cross metathesis with methyl acryl-ate. The cross metathesis products are amenable to stereoselective conjugate addition reactions and can be converted into either gamma-butyrolactones or gamma-lactams. KW - Lactams KW - Lactones KW - Oxygen heterocycles KW - Metathesis KW - Desymmetrization Y1 - 2011 U6 - https://doi.org/10.1002/ejoc.201001528 SN - 1434-193X IS - 9 SP - 1721 EP - 1727 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hölter, Frank T1 - Suzuki-Miyaura cross coupling reactions with Phenoldiazonium salts JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry N2 - The Suzuki-Miyaura coupling of phenol diazonium salts and aryl trifluoroborates yields 4-hydroxybiaryls in a protecting group-free synthesis. Y1 - 2011 U6 - https://doi.org/10.1039/c1ob05256j SN - 1477-0520 VL - 9 IS - 13 SP - 4914 EP - 4920 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Bernd A1 - Krehl, Stefan T1 - A single precatalyst tandem RCM-allylic oxidation sequence JF - Chemical communications N2 - Ring closing metathesis of allyloxy styrenes and a subsequent Ru-catalyzed allylic oxidation can be combined to a tandem sequence that makes coumarins accessible using less active but more conveniently available first generation catalysts. Y1 - 2011 U6 - https://doi.org/10.1039/c1cc11347j SN - 1359-7345 VL - 47 IS - 20 SP - 5879 EP - 5881 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Bernd A1 - Krehl, Stefan A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - Synthesis of 8-Aryl-Substituted Coumarins based on Ring-Closing Metathesis and Suzuki-Miyaura coupling - synthesis of a Furyl Coumarin natural product from Galipea panamensis JF - The journal of organic chemistry N2 - The synthesis of 7-methoxy-8-(4-methyl-3-furyl)-2H-chromen-2-one, a natural product with antileishmanial activity recently isolated from the plant Galipea panamensis, is described. The key step is a Suzuki-Miyaura coupling of a furan-3-boronic acid and an 8-halocoumarin, which is advantageously synthesized using a ring-closing metathesis reaction. Several non-natural analogues are also available along these lines. Y1 - 2012 U6 - https://doi.org/10.1021/jo2026564 SN - 0022-3263 VL - 77 IS - 5 SP - 2360 EP - 2367 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Kunz, Oliver T1 - alpha,beta-Unsaturated delta-Valerolactones through RCM-Isomerization Sequence JF - Synlett : accounts and rapid communications in synthetic organic chemistry N2 - alpha,beta-Unsaturated d-lactones are accessible via a sequential ring-closing metathesis (RCM) double-bond migration reaction starting from butenoates of allyl alcohols. This approach proceeds efficiently with lower catalyst loadings and higher initial substrate concentrations compared to the alternative RCM of acrylates derived from homoallylic alcohols. KW - ruthenium KW - lactones KW - tandem reactions KW - metathesis KW - esters Y1 - 2012 U6 - https://doi.org/10.1055/s-0031-1290488 SN - 0936-5214 IS - 6 SP - 851 EP - 854 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Krehl, Stefan A1 - Jablowski, Eric T1 - Assisted tandem catalytic RCM-aromatization in the synthesis of pyrroles and furans JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry N2 - An assisted tandem catalytic transformation of diallyl amines and diallyl ethers into N-aryl pyrroles and furans, respectively, is described. The sequence relies on ring closing metathesis followed by dehydrogenation of the initially formed dihydropyrroles and dihydrofurans. Both steps are Ru-catalyzed, but the sequence requires only one precatalyst, because conversion of the metathesis catalyst into the dehydrogenation catalyst is achieved in situ, triggered by the oxidant tert-butyl hydroperoxide. Y1 - 2012 U6 - https://doi.org/10.1039/c2ob25543j SN - 1477-0520 VL - 10 IS - 26 SP - 5119 EP - 5130 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli T1 - Selective arene functionalization through sequential oxidative and non-oxidative Heck reactions JF - Chemical communications N2 - A sequence of acetamide directed oxidative Heck reaction and deacetylation-diazotation-Heck coupling allows the traceless removal of the acetamide group and its dual exploitation as a catalyst directing group and a leaving group. Y1 - 2012 U6 - https://doi.org/10.1039/c2cc30752a SN - 1359-7345 VL - 48 IS - 36 SP - 4350 EP - 4352 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Bernd A1 - Kunz, Oliver A1 - Petersen, Monib H. T1 - Total syntheses of naturally occurring seimatopolide a and its enantiomer from chiral pool starting materials using a bidirectional strategy JF - The journal of organic chemistry N2 - Enantioselective total syntheses of both enantiomers of the recently isolated decanolide natural product seimatopolide A are described. The C-2-symmetric building blocks (R,R)-hexa-1,5-diene-3,4-diol (derived from D-mannitol) and its enantiomer (derived from L-(+)-tartrate) serve as key starting materials, which are elaborated in a bidirectional way using a selective mono-cross-metathesis, regio- and stereoselective epoxidation, and regioselective reductive epoxide opening to furnish the first fragment. Both enantiomers of the second fragment, 3-hydroxypent-4-enoic acid, were conveniently obtained through a lipase-catalyzed kinetic resolution and merged with the first fragment via Shiina esterification. An E-selective ring-closing metathesis was used to access the 10-membered lactone. A comparison of the specific optical rotations of synthetic seimatopolides with those reported for the natural product suggests that the originally assigned (3R,6R,7R,9S)-configuration should be corrected to (3S,6S,7S,9R). Y1 - 2012 U6 - https://doi.org/10.1021/jo302359h SN - 0022-3263 VL - 77 IS - 23 SP - 10897 EP - 10906 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Kunz, Oliver T1 - One-Flask tethered ring closing Metathesis-Electrocyclic ring opening for the highly stereoselective synthesis of conjugated Z/E-Dienes JF - European journal of organic chemistry N2 - A one-flask reaction sequence comprising ring closing metathesis (RCM) of butenoates derived from allylic alcohols and a base-mediated ring opening gives 2Z,4E-configured dienoic acids in high yields and stereoselectivities. Application of the method to the synthesis of the natural product fusanolide A suggests that the originally published structure was erroneously assigned and should be revised. KW - Natural products KW - Lactones KW - Macrocycles KW - Metathesis KW - Carboxylic -acids Y1 - 2012 U6 - https://doi.org/10.1002/ejoc.201101497 SN - 1434-193X IS - 5 SP - 1008 EP - 1018 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Paz, Cristian A1 - Peter, Martin G. A1 - Schmidt, Bernd A1 - Becerra, Jose A1 - Gutierrez, Margarita A1 - Astudillo, Luis A1 - Silva, Mario T1 - Synthesis and AChE inhibiting activity of 2, 4 substituted 6-Phenyl Pyrimidines JF - Journal of the Chilean Chemical Society N2 - Novel substituted pyrimidines were synthesized from methyl 2,4-dioxo-4-phenyl-butanoate (I-A) and urea, followed by Mitsunobu coupling of I-A with benzyl or allyl alcohol to give the corresponding 2-hydroxypyrimidine ethers in good yields. Saponification of I-A, followed by reaction with benzyl or allyl amines in the presence of TBTU yielded 2-hydroxy-6-phenyl-pyrimidine 4-carboxamides. AChE and BuChE assays revealed 2-hydroxy-6-phenyl-pyrimidine-4-carboxyallyamide as the most active compound, IC50=90 mu M, with no inhibition of BuChE. KW - Pyrimidines KW - inhibition AChE KW - mitsunobu KW - TBTU Y1 - 2012 SN - 0717-9324 VL - 57 IS - 3 SP - 1292 EP - 1294 PB - Sociedad Chilena De Quimica CY - Concepcion ER - TY - JOUR A1 - Schmidt, Bernd A1 - Krehl, Stefan A1 - Sotelo-Meza, Veronica T1 - Synthesis of chromanes through RCM-Transfer hydrogenation JF - Synthesis N2 - A sequential ruthenium-catalyzed ring-closing metathesis-transfer hydrogenation sequence has been established as a synthesis of chromanes starting from 2-(allyloxy)styrenes. The sequence requires only one precatalyst, the first-generation Grubbs catalyst, which is converted into a ruthenium hydride species in situ. Propan-2-ol serves as a chemical trigger for the formation of the ruthenium hydride and as hydrogen source. KW - ruthenium KW - chromanes KW - tandem reactions KW - metathesis KW - styrenes Y1 - 2012 U6 - https://doi.org/10.1055/s-0031-1289758 SN - 0039-7881 VL - 44 IS - 11 SP - 1603 EP - 1613 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Berger, René T1 - A deacetylation-diazotation-coupling sequence - palladium-catalyzed CC bond formation with acetanilides as formal leaving groups JF - Advanced synthesis & catalysis N2 - Acetanilides can be deacetylated and diazotized in situ, and subsequently used in Pd-catalyzed coupling reactions without isolation of the diazonium intermediate. Heck reactions, Suzuki cross-coupling reactions, and a Pd-catalyzed [2+2+1]cycloaddition have been investigated as terminating CC bond-forming steps of this one-flask sequence. The sequence does not require the exchange of solvents or removal of by-products between the individual steps, but proceeds by addition of reagents and catalysts in due course. KW - diazo compounds KW - Heck reaction KW - homogeneous catalysis KW - palladium KW - Suzuki coupling Y1 - 2013 U6 - https://doi.org/10.1002/adsc.201200929 SN - 1615-4150 VL - 355 IS - 2-3 SP - 463 EP - 476 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Krehl, Stefan A1 - Hauke, Sylvia T1 - Assisted tandem catalytic cross metathesis-oxidation in one flask from styrenes to 1,2-Diketones and further to quinoxalines JF - The journal of organic chemistry N2 - 1,2-Diketones were synthesized from styrenes by combining a cross metathesis and a Ru-catalyzed alkene oxidation to an assisted tandem catalytic sequence. The synthesis relies on the use of just one metathesis precatalyst, which was in situ converted to the oxidation catalyst by addition of an alkyl hydroperoxide as a chemical trigger and oxidant. The one-flask sequence can be extended beyond 1,2-diketones to quinoxalines, by condensation of the oxidation products with ortho-phenylenediamine. Y1 - 2013 U6 - https://doi.org/10.1021/jo4005684 SN - 0022-3263 VL - 78 IS - 11 SP - 5427 EP - 5435 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin A1 - Karras, Manfred T1 - 2,2 '-Biphenols via protecting group-free thermal or microwave-accelerated suzuki-miyaura coupling in water JF - The journal of organic chemistry N2 - User-friendly protocols for the protecting group-free synthesis of 2,2'-biphenols via Suzuki-Miyaura coupling of o-halophenols and o-boronophenol are presented. The reactions proceed in water in the presence of simple additives such as K2CO3, KOH, KF, or TBAF and with commercially available Pd/C as precatalyst. Expensive or laboriously synthesized ligands or other additives are not required. In the case of bromophenols, efficient rate acceleration and short reaction times were accomplished by microwave irradiation. Y1 - 2013 U6 - https://doi.org/10.1021/jo401398n SN - 0022-3263 VL - 78 IS - 17 SP - 8680 EP - 8688 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Kunz, Oliver T1 - Stereoselective synthesis of dienyl phosphonates via extended tethered ring-closing metathesis JF - Organic letters N2 - Allylphosphonates of allylic alcohols were converted to conjugated dienyl phosphonates in a one-flask reaction, comprising a ring-closing metathesis (RCM), a base-induced ring-opening, and an alkylation. The ring-opening proceeds with very high diastereoselectivity, giving exclusively the (1Z,3E)-configured dienes. Single diastereomers and mixtures of diastereomers can be used as starting materials without noticeable effect on the diastereoselectivity of the sequence. Y1 - 2013 U6 - https://doi.org/10.1021/ol4020078 SN - 1523-7060 SN - 1523-7052 VL - 15 IS - 17 SP - 4470 EP - 4473 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Kunz, Oliver T1 - Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C-2-symmetric building block: a strategy for the synthesis of decanolide natural products JF - Beilstein journal of organic chemistry N2 - Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru-lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation. KW - dienes KW - enzyme catalysis KW - lactones KW - metathesis KW - natural products KW - ruthenium Y1 - 2013 U6 - https://doi.org/10.3762/bjoc.9.289 SN - 1860-5397 VL - 9 SP - 2544 EP - 2555 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, Main ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Berger, René A1 - Petersen, Monib H. T1 - From paracetamol to rolipram and derivatives - application of deacetylation-diazotation sequences and palladium-catalyzed matsuda-heck reaction JF - Synthesis N2 - A six-step synthesis of the antidepressant rolipram from the popular analgetic 4-acetamidophenol (paracetamol) is described. The steps include oxidative functionalization of the aromatic core, diazonium salt formation via deacetylation-diazotation, Matsuda-Heck reaction, conjugate addition of nitromethane, and hydrogenative cyclization. KW - acetanilides KW - deacetylation KW - diazonium salts KW - palladium KW - Matsuda-Heck reaction Y1 - 2013 U6 - https://doi.org/10.1055/s-0032-1316874 SN - 0039-7881 VL - 45 IS - 9 SP - 1174 EP - 1180 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hauke, Sylvia T1 - Cross metathesis of allyl alcohols how to suppress and how to promote double bond isomerization JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry N2 - Under standard conditions the cross metathesis of allyl alcohols and methyl acrylate is accompanied by the formation of ketones, resulting from uncontrolled and undesired double bond isomerization. By conducting the CM in the presence of phenol, the catalyst loading and the reaction time required for quantiative conversion can be reduced, and isomerization can be suppressed. On the other hand, consecutive isomerization can be deliberately promoted by evaporating excess methyl acrylate after completing cross metathesis and by adding a base or silane as chemical triggers. Y1 - 2013 U6 - https://doi.org/10.1039/c3ob40167g SN - 1477-0520 VL - 11 IS - 25 SP - 4194 EP - 4206 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Berger, René A1 - Hoelter, Frank T1 - Scope and limitations of the Heck-Matsuda-coupling of phenol diazonium salts and styrenes a protecting-group economic synthesis of phenolic stilbenes JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry N2 - 4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4'-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior. Y1 - 2013 U6 - https://doi.org/10.1039/c3ob40420j SN - 1477-0520 VL - 11 IS - 22 SP - 3674 EP - 3691 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Berger, René A1 - Hölter, Frank T1 - Scope and limitations of the Heck-Matsuda-coupling of phenol diazonium salts and styrenes: a protecting-group economic synthesis of phenolic stilbenes N2 - 4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4ï-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior. Y1 - 2014 UR - http://pubs.rsc.org/en/content/articlepdf/2013/ob/c3ob40420j U6 - https://doi.org/10.1039/C3OB40420J SN - 1477-0520 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hauke, Sylvia T1 - Cross metathesis of allyl alcohols: how to suppress and how to promote double bond isomerization N2 - Under standard conditions the cross metathesis of allyl alcohols and methyl acrylate is accompanied by the formation of ketones, resulting from uncontrolled and undesired double bond isomerization. By conducting the CM in the presence of phenol, the catalyst loading and the reaction time required for quantiative conversion can be reduced, and isomerization can be suppressed. On the other hand, consecutive isomerization can be deliberately promoted by evaporating excess methyl acrylate after completing cross metathesis and by adding a base or silane as chemical triggers. Y1 - 2014 UR - http://pubs.rsc.org/en/content/articlepdf/2013/ob/c3ob40167g U6 - https://doi.org/10.1039/c3ob40167g SN - 1477-0520 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin A1 - Schilde, Uwe T1 - Chroman-4-ones via microwave-promoted domino claisen rearrangement-oxa-michael addition: Synthesis of tabchromones A and B JF - Synlett : accounts and rapid communications in synthetic organic chemistry N2 - Allyl phenyl ethers with a pendant enone substituent undergo, upon microwave irradiation, a domino sequence of Claisen rearrangement and 6-endo-trig-cyclization to furnish functionalized chroman-4-ones. The natural products tabchromones A and B were synthesized via this method. KW - cyclization KW - Michael addition KW - rearrangement KW - tandem reaction KW - Wacker reaction Y1 - 2014 U6 - https://doi.org/10.1055/s-0034-1379364 SN - 0936-5214 SN - 1437-2096 VL - 25 IS - 20 SP - 2943 EP - 2946 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hauke, Sylvia T1 - Metathesis-Based de novo synthesis of noviose JF - European journal of organic chemistry N2 - The rare carbohydrate L-(+)-noviose was synthesized from enantiomerically pure L-lactate. The configuration at C-4 was established by diastereoselective nucleophilic addition to an in-situ-generated lactaldehyde. The resulting homoallylic alcohol was further transformed into a set of ring-closing metathesis (RCM) precursors. These compounds were converted into noviose in few steps using RCM and RCM-allylic-oxidation sequences. KW - Carbohydrates KW - Allylic oxidation KW - Oxygen heterocycles KW - Metathesis KW - Ruthenium Y1 - 2014 U6 - https://doi.org/10.1002/ejoc.201301615 SN - 1434-193X SN - 1099-0690 VL - 2014 IS - 9 SP - 1951 EP - 1960 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hauke, Sylvia A1 - Muehlenberg, Nino T1 - Imino glycals via Ruthenium-catalyzed RCM and isomerization JF - Synthesis N2 - N-Allyl-N-homoallylamines were converted in one step into cyclic enamides via a ruthenium-catalyzed assisted tandem catalytic ring-closing metathesis-isomerization sequence. The sequence relies on the in situ transformation of a metathesis active Ru-carbene into an isomerization active Ru-hydride by addition of hydroxide as a chemical trigger. KW - heterocycles KW - isomerization KW - metathesis KW - ruthenium KW - tandem reaction Y1 - 2014 U6 - https://doi.org/10.1055/s-0033-1338615 SN - 0039-7881 SN - 1437-210X VL - 46 IS - 12 SP - 1648 EP - 1658 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hauke, Sylvia T1 - Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative JF - Beilstein journal of organic chemistry N2 - Cross metathesis of a lactate derived allylic alcohol and acrolein is the entry point to a de novo synthesis of 4-benzoate protected L-amicetose and a cinerulose derivative protected at C5 and C1. KW - carbohydrates KW - de novo synthesis KW - lactate KW - metathesis KW - ruthenium Y1 - 2014 U6 - https://doi.org/10.3762/bjoc.10.102 SN - 1860-5397 VL - 10 SP - 1023 EP - 1031 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, Main ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin T1 - Suzuki-Miyaura coupling of halophenols and phenol boronic acids: systematic investigation of positional isomer effects and conclusions for the synthesis of phytoalexins from Pyrinae JF - The journal of organic chemistry N2 - The Suzuki-Miyaura couplings of o-, m-, and p-halophenols with o-, m-, and p-phenol boronic acids were investigated for all combinations under standardized conditions, using Pd/C as a heterogeneous catalyst and water as a solvent. In the case of iodophenols, conventional heating was used, while for bromophenols significantly better results could be obtained using microwave irradiation. This systematic study revealed that 2,4'-biphenol is particularly difficult to access, irrespective of the starting materials used, but that these difficulties can be overcome by using different additives. The conclusions drawn from this investigation allowed us to identify conditions for the protecting group-free or minimized total synthesis of biaryl-type phytoalexins. These compounds possess antibacterial activity and are produced by fruit trees as a response to microbial infection. Y1 - 2014 U6 - https://doi.org/10.1021/jo500675a SN - 0022-3263 VL - 79 IS - 9 SP - 4104 EP - 4118 PB - American Chemical Society CY - Washington ER - TY - BOOK A1 - Buddrus, Joachim A1 - Schmidt, Bernd T1 - Grundlagen der organischen Chemie Y1 - 2015 SN - 978-3-11-030559-3 PB - de Gruyter CY - Berlin ET - 5., überarb. und aktualisierte Aufl. ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Schilde, Uwe A1 - Kelling, Alexandra T1 - Dual Role of Acetanilides: Traceless Removal of a Directing Group through Deacetylation/Diazotation and Palladium-Catalyzed C-C-Coupling Reactions JF - The journal of organic chemistry N2 - The acetamide group enables regioselective oxidative ortho-C-H activation reactions, such as Pd-catalyzed acylation. The synthetic utility of these transformations can be significantly enhanced by using the acetamide as a quasi-leaving group in a subsequent conventional Pd-catalyzed coupling or cross-coupling reaction. The concept is illustrated herein for the synthesis of o-alkenyl- and o-arylphenones, which have potential for the synthesis of arylated aromatic heterocycles. Y1 - 2015 U6 - https://doi.org/10.1021/acs.joc.5b00272 SN - 0022-3263 VL - 80 IS - 9 SP - 4223 EP - 4234 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin T1 - Synthesis of Magnaldehydes B and E and Dictyobiphenyl B by Microwave-Promoted Cross-Coupling of Boronophenols JF - European journal of organic chemistry N2 - Magnaldehydes B and E along with their 4'-methylated derivatives are naturally occurring 2,4'-biphenols that have been isolated from the Magnoliaceae. Herein, these natural products have been synthesized from a common intermediate, which was obtained by a microwave-promoted, hetero-geneously catalyzed, and protecting-group-free Suzuki-Miyaura coupling reaction in an aqueous medium. These reaction conditions were also successfully applied to a one-step synthesis of the slime mold metabolite dictyobiphenyl B. KW - Total synthesis KW - Natural products KW - Cross-coupling KW - Palladium KW - Biaryls KW - Phenols Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201500350 SN - 1434-193X SN - 1099-0690 IS - 17 SP - 3760 EP - 3766 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Riemer, Nastja A1 - Hölter, Frank T1 - Acetamidoarenediazonium Salts: Opportunities for Multiple Arene Functionalization JF - European journal of organic chemistry N2 - Unlike their ortho counterparts, meta- and para-acetamidoanilines can be converted into the corresponding acetamidoarenediazonium salts. These offer various opportunities for multiple Pd-catalyzed arene functionalization reactions, such as Matsuda-Heck-, Suzuki-Miyaura- or Fujiwara-Moritani couplings. KW - Arenes KW - Amides KW - C-C coupling KW - Cross-coupling KW - Palladium Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201500795 SN - 1434-193X SN - 1099-0690 IS - 26 SP - 5826 EP - 5841 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Paz, Cristian A1 - Becerra, Jose A1 - Silva, Mario A1 - Burgos, Viviana A1 - Heydenreich, Matthias A1 - Schmidt, Bernd A1 - Thu Tran, A1 - Vetter, Irina T1 - (-)-Pentylsedinine, a New Alkaloid from the Leaves of Lobelia tupa with Agonist Activity at Nicotinic Acetylcholine Receptor JF - Natural product communications : an international journal for communications and reviews N2 - Lobelia tupa, also called devil's tobacco, is a native plant from the center-south of Chile which has been used by the native people of Chile as a hallucinogenic and anesthetic plant. A new piperidine alkaloid, called pentylsedinine, which comprises five carbons in the side chain, was isolated from the aerial part of L. tupa, along with lobeline and lobelanidine. The structure was established on the basis of 1D and 2D NMR spectroscopy. While lobeline is a neutral antagonist at alpha 3 beta 2/alpha 3 beta 4 nAChR and alpha 7 nAChR, both lobelanidine and pentylsedinine act as partial agonists at nAChR KW - Lobelia tupa KW - Piperidine alkaloid KW - nAChR KW - Pentylsedinine Y1 - 2015 SN - 1934-578X SN - 1555-9475 VL - 10 IS - 8 SP - 1355 EP - 1357 PB - NPC CY - Westerville ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin A1 - Schilde, Uwe T1 - Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones JF - European journal of organic chemistry N2 - Allyl, dimethylallyl and prenyl ethers derived from o-acyl-phenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandem Claisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones. The method is potentially useful for the synthesis of natural products and drugs. KW - Allylic compounds KW - Arenes KW - Oxygen heterocycles KW - Microwave chemistry KW - Rearrangement KW - Michael addition Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201501151 SN - 1434-193X SN - 1099-0690 IS - 34 SP - 7602 EP - 7611 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin T1 - Microwave-Promoted Deprenylation: Prenyl Ether as a Thermolabile Phenol Protecting Group JF - Synthesis N2 - para-Substituted aryl prenyl ethers undergo a deprenylation reaction upon microwave irradiation. This offers the opportunity to use a prenyl ether as a thermolabile protecting group in the synthesis of natural products with a chromone structure, which proceeds via a tandem deprenylation/6-endo-cyclization sequence. KW - microwave irradiation KW - phenols KW - chromenes KW - protecting groups KW - Claisen rearrangement Y1 - 2016 U6 - https://doi.org/10.1055/s-0035-1561366 SN - 0039-7881 SN - 1437-210X VL - 48 SP - 1399 EP - 1406 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Audoersch, Stephan A1 - Kunz, Oliver T1 - Stereoselective Synthesis of 2Z,4E-Configured Dienoates through Tethered Ring Closing Metathesis JF - Synthesis KW - allyl alcohols KW - dienes KW - ring closing metathesis KW - ruthenium KW - elimination Y1 - 2016 U6 - https://doi.org/10.1055/s-0035-1562536 SN - 0039-7881 SN - 1437-210X VL - 48 SP - 4509 EP - 4518 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Schmidt, Bernd A1 - Wolf, Felix A1 - Ehlert, Christopher T1 - Systematic Investigation into the Matsuda-Heck Reaction of alpha-Methylene Lactones: How Conformational Constraints Direct the beta-H-Elimination Step JF - The journal of organic chemistry N2 - alpha-Methylene-gamma-butyrolactone and alpha-methylene-gamma-valerolactone undergo Pd-catalyzed Matsuda-Heck couplings with arene diazonium salts to alpha-benzyl butenolides or pentenolides, respectively, or to alpha-benzylidene lactones. The observed regioselectivity is strongly ring size dependent, with six-membered rings giving exclusively alpha-benzyl pentenolides, whereas the five-membered alpha-methylene lactone reacts to mixtures of regioisomers with a high proportion of (E)-alpha-benzylidene-gamma-butyrolactones. DFT calculations suggest that the reasons for these differences are not thermodynamic but kinetic in nature. The relative energies of the conformers of the Pd sigma-complexes resulting from insertion into the Pd-aryl bond were correlated with the dihedral angles between Pd and endo-beta-H. This correlation revealed that in the case of the six-membered lactone an energetically favorable conformer adopts a nearly synperiplanar Pd/endo-beta-H arrangement, whereas for the analogous Pd sigma-complex of the five-membered lactone the smallest Pd/endo-beta-H dihedral angle is observed for a conformer with a comparatively high potential energy. The optimized conditions for Matsuda-Heck arylations of exo-methylene lactones were eventually applied to the synthesis of the natural product anemarcoumarin A. Y1 - 2016 U6 - https://doi.org/10.1021/acs.joc.6b02207 SN - 0022-3263 VL - 81 SP - 11235 EP - 11249 PB - American Chemical Society CY - Washington ER -