@article{SchmidtStaude2006, author = {Schmidt, Bernd and Staude, Lucia}, title = {Unexpected transfer hydrogenation of C-C-double bonds during Tandem-RCM-isomerization reactions}, series = {Journal of organometallic chemistry}, volume = {691}, journal = {Journal of organometallic chemistry}, number = {24-25}, publisher = {Elsevier}, address = {Lausanne}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2006.07.011}, pages = {5218 -- 5221}, year = {2006}, abstract = {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.}, language = {en} } @article{KwesigaKellingKerstingetal.2020, author = {Kwesiga, George and Kelling, Alexandra and Kersting, Sebastian and Sperlich, Eric and von Nickisch-Rosenegk, Markus and Schmidt, Bernd}, title = {Total syntheses of prenylated isoflavones from Erythrina sacleuxii and their antibacterial activity}, series = {Journal of natural products}, volume = {83}, journal = {Journal of natural products}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {0163-3864}, doi = {10.1021/acs.jnatprod.0c00932}, pages = {3445 -- 3453}, year = {2020}, abstract = {The prenylated isoflavones 5-deoxyprenylbiochanin A (7-hydroxy-4'-methoxy-3'-prenylisoflavone) and erysubin F (7,4'-dihydroxy-8,3'-diprenylisoflavone) were synthesized for the first time, starting from mono-or di-O-allylated chalcones, and the structure of 5-deoxy-3'-prenylbiochanin A was corroborated by single-crystal X-ray diffraction analysis. Flavanones are key intermediates in the synthesis. Their reaction with hypervalent iodine reagents affords isoflavones via a 2,3-oxidative rearrangement and the corresponding flavone isomers via 2,3-dehydrogenation. This enabled a synthesis of 7,4'-dihydroxy-8,3'-diprenylflavone, a non-natural regioisomer of erysubin F. Erysubin F (8), 7,4'-dihydroxy-8,3'-diprenylflavone (27), and 5-deoxy-3'prenylbiochanin A (7) were tested against three bacterial strains and one fungal pathogen. All three compounds are inactive against Salmonella enterica subsp. enterica (NCTC 13349), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028), with MIC values greater than 80.0 mu M. The diprenylated natural product erysubin F (8) and its flavone isomer 7,4'-dihydroxy-8,3'diprenylflavone (27) show in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA, ATCC 43300) at MIC values of 15.4 and 20.5 mu M, respectively. In contrast, the monoprenylated 5-deoxy-3'-prenylbiochanin A (7) is inactive against this MRSA strain.}, language = {en} } @article{SchmidtKunzPetersen2012, author = {Schmidt, Bernd and Kunz, Oliver and Petersen, Monib H.}, title = {Total syntheses of naturally occurring seimatopolide a and its enantiomer from chiral pool starting materials using a bidirectional strategy}, series = {The journal of organic chemistry}, volume = {77}, journal = {The journal of organic chemistry}, number = {23}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo302359h}, pages = {10897 -- 10906}, year = {2012}, abstract = {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).}, language = {en} } @article{PazHeydenreichSchmidtetal.2018, author = {Paz, Cristian and Heydenreich, Matthias and Schmidt, Bernd and Vadra, Nahir and Baggio, Ricardo}, title = {Three new dihydro-beta-agarofuran sesquiterpenes from the seeds of Maytenus boaria}, series = {Acta Crystallographica Section C}, volume = {74}, journal = {Acta Crystallographica Section C}, publisher = {International Union of Crystallography}, address = {Chester}, issn = {2053-2296}, doi = {10.1107/S2053229618005429}, pages = {564 -- 570}, year = {2018}, abstract = {As part of a project studying the secondary metabolites extracted from the Chilean flora, we report herein three new beta-agarofuran sesquiterpenes, namely (1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9-dihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b] oxepine-5,10-diylbis(furan-3-carboxylate), C27H32O11, (II), (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-9-hydroxy-2,2,5a, 9-tetramethyloctahydro-2H-3,9a-methanobenzo[ b] oxepine-5,10-diyl bis(furan-3-carboxylate), C27H32O10, (III), and (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-10-(benzoyloxy)-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepin-5-yl furan-3-carboxylate, C29H34O9, (IV), obtained from the seeds of Maytenus boaria and closely associated with a recently published relative [Paz et al. (2017). Acta Cryst. C73, 451-457]. In the (isomorphic) structures of (II) and (III), the central decalin system is esterified with an acetate group at site 1 and furoate groups at sites 6 and 9, and differ at site 8, with an OH group in (II) and no substituent in (III). This position is also unsubstituted in (IV), with site 6 being occupied by a benzoate group. The chirality of the skeletons is described as 1S, 4S, 5S, 6R, 7R, 8R, 9R, 10S in (II) and 1S, 4S, 5S, 6R, 7R, 9S, 10S in (III) and (IV), matching the chirality suggested by NMR studies. This difference in the chirality sequence among the title structures (in spite of the fact that the three skeletons are absolutely isostructural) is due to the differences in the environment of site 8, i.e. OH in (II) and H in (III) and (IV). This diversity in substitution, in turn, is responsible for the differences in the hydrogen-bonding schemes, which is discussed.}, language = {en} } @article{SchmidtWernerKellingetal.2010, author = {Schmidt, Bernd and Werner, Frank and Kelling, Alexandra and Schilde, Uwe}, title = {The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride : formation and crystal structure analysis of an unexpected bicyclic product}, issn = {0022-152X}, year = {2010}, abstract = {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.}, language = {en} } @article{SchmidtRiemerSchilde2015, author = {Schmidt, Bernd and Riemer, Martin and Schilde, Uwe}, title = {Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, number = {34}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-193X}, doi = {10.1002/ejoc.201501151}, pages = {7602 -- 7611}, year = {2015}, abstract = {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.}, language = {en} } @article{SchmidtWolfEhlert2016, author = {Schmidt, Bernd and Wolf, Felix and Ehlert, Christopher}, title = {Systematic Investigation into the Matsuda-Heck Reaction of alpha-Methylene Lactones: How Conformational Constraints Direct the beta-H-Elimination Step}, series = {The journal of organic chemistry}, volume = {81}, journal = {The journal of organic chemistry}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b02207}, pages = {11235 -- 11249}, year = {2016}, abstract = {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.}, language = {en} } @article{SchmidtWolf2017, author = {Schmidt, Bernd and Wolf, Felix}, title = {Synthesis of Phenylpropanoids via Matsuda-Heck Coupling of Arene Diazonium Salts}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.7b00447}, pages = {4386 -- 4395}, year = {2017}, abstract = {The Pd-catalyzed Heck-type coupling (Matsuda Heck reaction) of electron rich arene diazonium salts with electron deficient olefins has been exploited for the synthesis of phenylpropanoid natural products. Examples described herein are the naturally occurring benzofurans methyl wutaifuranate, wutaifuranol, wutaifuranal, their 7-methoxy derivatives, and the O-prenylated natural products boropinols A and C.}, language = {en} } @article{SchmidtRiemer2015, author = {Schmidt, Bernd and Riemer, Martin}, title = {Synthesis of Magnaldehydes B and E and Dictyobiphenyl B by Microwave-Promoted Cross-Coupling of Boronophenols}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, number = {17}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-193X}, doi = {10.1002/ejoc.201500350}, pages = {3760 -- 3766}, year = {2015}, abstract = {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.}, language = {en} } @article{SchmidtKrehlSoteloMeza2012, author = {Schmidt, Bernd and Krehl, Stefan and Sotelo-Meza, Veronica}, title = {Synthesis of chromanes through RCM-Transfer hydrogenation}, series = {Synthesis}, volume = {44}, journal = {Synthesis}, number = {11}, publisher = {Thieme}, address = {Stuttgart}, issn = {0039-7881}, doi = {10.1055/s-0031-1289758}, pages = {1603 -- 1613}, year = {2012}, abstract = {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.}, language = {en} } @article{RiemerRiemerKruegeretal.2021, author = {Riemer, Nastja and Riemer, Martin and Kr{\"u}ger, Mandy and Clarkson, Guy J. and Shipman, Michael and Schmidt, Bernd}, title = {Synthesis of arylidene-beta-lactams via exo-selective Matsuda-Heck arylation of methylene-beta-lactams}, series = {The journal of organic chemistry : JOC}, volume = {86}, journal = {The journal of organic chemistry : JOC}, number = {13}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.1c00638}, pages = {8786 -- 8796}, year = {2021}, abstract = {exo-Methylene-beta-lactams were synthesized in two steps from commercially available 3-bromo-2-(bromomethyl)-propionic acid and reacted with arene diazonium salts in a Heck-type arylation in the presence of catalytic amounts of Pd(OAc)(2) under ligand-free conditions. The products, arylidene-beta-lactams, were obtained in high yields as single isomers. The beta-hydride elimination step of the Pd-catalyzed coupling reaction proceeds with high exo-regioselectivity and E-stereoselectivity. With aryl iodides, triflates, or bromides, the coupling products were isolated only in low yields, due to extensive decomposition of the starting material at elevated temperatures. This underlines that arene diazonium salts can be superior arylating reagents in Heck-type reactions and yield coupling products in synthetically useful yields and selectivities when conventional conditions fail.}, language = {en} } @article{SchmidtRiemer2016, author = {Schmidt, Bernd and Riemer, Martin}, title = {Synthesis of Allyl- and Prenylcoumarins via Microwave-Promoted Tandem Claisen Rearrangement/Wittig Olefination}, series = {Synthesis}, volume = {48}, journal = {Synthesis}, publisher = {Thieme}, address = {Stuttgart}, issn = {0039-7881}, doi = {10.1055/s-0035-1560501}, pages = {141 -- 149}, year = {2016}, abstract = {Allyl, dimethylallyl, crotyl, and prenyl ethers of various aromatic ortho-hydroxy carbonyl compounds undergo a tandem sequence of Claisen rearrangement, carbonyl olefination, and cyclization upon microwave irradiation in the presence of a stabilized ylide. The products are multiply substituted 6- or 8-allylated or prenylated coumarins (2H-chromen-2-ones).}, language = {en} } @article{SchmidtKrehlKellingetal.2012, author = {Schmidt, Bernd and Krehl, Stefan and Kelling, Alexandra and Schilde, Uwe}, title = {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}, series = {The journal of organic chemistry}, volume = {77}, journal = {The journal of organic chemistry}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo2026564}, pages = {2360 -- 2367}, year = {2012}, abstract = {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.}, language = {en} } @article{NchiozemNgnitedemSperlichMatietaetal.2023, author = {Nchiozem-Ngnitedem, Vaderament-Alexe and Sperlich, Eric and Matieta, Valaire Yemene and Kuete, Jenifer Reine Ngnouzouba and Kuete, Victor and Omer, Ejlal A. A. and Efferth, Thomas and Schmidt, Bernd}, title = {Synthesis and bioactivity of isoflavones from ficus carica and some non-natural analogues}, series = {Journal of natural products : Lloydia}, volume = {86}, journal = {Journal of natural products : Lloydia}, number = {6}, publisher = {American Chemical Society}, address = {Washington, DC}, issn = {0163-3864}, doi = {10.1021/acs.jnatprod.3c00219}, pages = {1520 -- 1528}, year = {2023}, abstract = {FicucariconeD (1) and its 4 '-demethyl congener 2 are isoflavones isolated from fruits of Ficus carica that share a 5,7-dimethoxy-6-prenyl-substituted A-ring. Both naturalproducts were, for the first time, obtained by chemical synthesisin six steps, starting from 2,4,6-trihydroxyacetophenone. Key stepsare a microwave-promoted tandem sequence of Claisen- and Cope-rearrangementsto install the 6-prenyl substituent and a Suzuki-Miyaura crosscoupling for installing the B-ring. By using various boronic acids,non-natural analogues become conveniently available. All compoundswere tested for cytotoxicity against drug-sensitive and drug-resistanthuman leukemia cell lines, but were found to be inactive. The compoundswere also tested for antimicrobial activities against a panel of eightGram-negative and two Gram-positive bacterial strains. Addition ofthe efflux pump inhibitor phenylalanine-arginine-beta-naphthylamide(PA beta N) significantly improved the antibiotic activity in mostcases, with MIC values as low as 2.5 mu M and activity improvementfactors as high as 128-fold.}, language = {en} } @article{PazPeterSchmidtetal.2012, author = {Paz, Cristian and Peter, Martin G. and Schmidt, Bernd and Becerra, Jose and Gutierrez, Margarita and Astudillo, Luis and Silva, Mario}, title = {Synthesis and AChE inhibiting activity of 2, 4 substituted 6-Phenyl Pyrimidines}, series = {Journal of the Chilean Chemical Society}, volume = {57}, journal = {Journal of the Chilean Chemical Society}, number = {3}, publisher = {Sociedad Chilena De Quimica}, address = {Concepcion}, issn = {0717-9324}, pages = {1292 -- 1294}, year = {2012}, abstract = {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.}, language = {en} } @article{SchmidtHoelter2011, author = {Schmidt, Bernd and H{\"o}lter, Frank}, title = {Suzuki-Miyaura cross coupling reactions with Phenoldiazonium salts}, series = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, volume = {9}, journal = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1477-0520}, doi = {10.1039/c1ob05256j}, pages = {4914 -- 4920}, year = {2011}, abstract = {The Suzuki-Miyaura coupling of phenol diazonium salts and aryl trifluoroborates yields 4-hydroxybiaryls in a protecting group-free synthesis.}, language = {en} } @article{SchmidtRiemer2014, author = {Schmidt, Bernd and Riemer, Martin}, title = {Suzuki-Miyaura coupling of halophenols and phenol boronic acids: systematic investigation of positional isomer effects and conclusions for the synthesis of phytoalexins from Pyrinae}, series = {The journal of organic chemistry}, volume = {79}, journal = {The journal of organic chemistry}, number = {9}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo500675a}, pages = {4104 -- 4118}, year = {2014}, abstract = {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.}, language = {en} } @article{ZhaoSarhanEljarratetal.2022, author = {Zhao, Yuhang and Sarhan, Radwan Mohamed and Eljarrat, Alberto and Kochovski, Zdravko and Koch, Christoph and Schmidt, Bernd and Koopman, Wouter-Willem Adriaan and Lu, Yan}, title = {Surface-functionalized Au-Pd nanorods with enhanced photothermal conversion and catalytic performance}, series = {ACS applied materials \& interfaces}, volume = {14}, journal = {ACS applied materials \& interfaces}, number = {15}, publisher = {American Chemical Society}, address = {Washington, DC}, issn = {1944-8244}, doi = {10.1021/acsami.2c00221}, pages = {17259 -- 17272}, year = {2022}, abstract = {Bimetallic nanostructures comprising plasmonic and catalytic components have recently emerged as a promising approach to generate a new type of photo-enhanced nanoreactors. Most designs however concentrate on plasmon-induced charge separation, leaving photo-generated heat as a side product. This work presents a photoreactor based on Au-Pd nanorods with an optimized photothermal conversion, which aims to effectively utilize the photo-generated heat to increase the rate of Pd-catalyzed reactions. Dumbbell-shaped Au nanorods were fabricated via a seed-mediated growth method using binary surfactants. Pd clusters were selectively grown at the tips of the Au nanorods, using the zeta potential as a new synthetic parameter to indicate the surfactant remaining on the nanorod surface. The photothermal conversion of the Au-Pd nanorods was improved with a thin layer of polydopamine (PDA) or TiO2. As a result, a 60\% higher temperature increment of the dispersion compared to that for bare Au rods at the same light intensity and particle density could be achieved. The catalytic performance of the coated particles was then tested using the reduction of 4-nitrophenol as the model reaction. Under light, the PDA-coated Au-Pd nanorods exhibited an improved catalytic activity, increasing the reaction rate by a factor 3. An analysis of the activation energy confirmed the photoheating effect to be the dominant mechanism accelerating the reaction. Thus, the increased photothermal heating is responsible for the reaction acceleration. Interestingly, the same analysis shows a roughly 10\% higher reaction rate for particles under illumination compared to under dark heating, possibly implying a crucial role of localized heat gradients at the particle surface. Finally, the coating thickness was identified as an essential parameter determining the photothermal conversion efficiency and the reaction acceleration.}, language = {en} } @article{SchmidtWolfBrunner2016, author = {Schmidt, Bernd and Wolf, Felix and Brunner, Heiko}, title = {Styrylsulfonates and -Sulfonamides through Pd-Catalysed Matsuda-Heck Reactions of Vinylsulfonic Acid Derivatives and Arenediazonium Salts}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-193X}, doi = {10.1002/ejoc.201600469}, pages = {2972 -- 2982}, year = {2016}, abstract = {Arene diazonium salts undergo Matsuda-Heck reactions with vinylsulfonates and -sulfonamides to give styrylsulfonic acid derivatives in high to excellent yields and with high to excellent selectivities. By quantifying the evolution of nitrogen over time in a gas-meter apparatus, the reactivities of ethylvinylsulfonate and the benchmark olefin methyl acrylate were compared for an electron-rich and an -deficient arene diazonium salt. Tertiary sulfonamides react in Matsuda-Heck couplings with high conversions, but require long reaction times, which prevents the determination of kinetic data through the measurement of nitrogen evolution. Secondary sulfonamides were found to be unreactive. From these results, the following order of reactivity could be deduced: H2C=CHCO2Me > H2C=CHSO2OEt > H2C=CHSO2N(Me)Bn >> H2C=CHSO2NHBn. Through the Matsuda-Heck coupling of 5-indolyldiazonium salt and a tertiary vinylsulfonamide, the synthesis of the C-5-substituted indole part of the antimigraine drug naratriptan was accomplished in high yield.}, language = {en} } @article{SchmidtAudoersch2017, author = {Schmidt, Bernd and Aud{\"o}rsch, Stephan}, title = {Stereoselective Total Syntheses of Polyacetylene Plant Metabolites via Ester-Tethered Ring Closing Metathesis}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, number = {3}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b02987}, pages = {1743 -- 1760}, year = {2017}, abstract = {Total syntheses of five naturally occurring polyacetylenes from three different plants are described. These natural products have in common an E,Z-configured conjugated diene linked to a di-or triyne chain. As the key method to stereoselectively establish the E,Z-diene part, an ester-tethered ring-closing metathesis/base-induced eliminative ring opening sequence was used. The results presented herein do not only showcase the utility of this tethered RCM variant but have also prompted us to suggest that the originally assigned absolute configurations of chiral polyacetylenes from Atractylodes macrocephala should be revised or at least reconsidered.}, language = {en} }