TY - JOUR A1 - Karras, Manfred A1 - Dabrowski, Michal A1 - Pohl, Radek A1 - Rybacek, Jiri A1 - Vacek, Jaroslav A1 - Bednarova, Lucie A1 - Grela, Karol A1 - Stary, Ivo A1 - Stara, Irena G. A1 - Schmidt, Bernd T1 - Helicenes as Chirality-Inducing Groups in Transition-Metal Catalysis BT - the first helically chiral Olefin Metathesis Catalyst JF - Chemistry - a European journal N2 - Helical chirality is a novel enantioselectivity-inducing property in transition-metal-catalyzed transformations. The principle is illustrated herein for the example of asymmetric olefin metathesis. This work reports the synthesis of the first helically chiral Ru-NHC alkylidene complex from an aminohelicene-derived imidazolium salt, which was ligated to the first generation Hoveyda-Grubbs catalyst. Kinetic data were acquired for benchmark test reactions and compared to an achiral catalyst. The helically chiral Ru-catalyst was evaluated in asymmetric ring-closing metathesis (RCM) and ring-opening metathesis-cross-metathesis (ROM/CM) reactions, which proceeded with promising levels of enantioselectivity. Extensive NMR-spectroscopic investigations and a DFT geometry optimization were performed. These results led to a topographic steric map and calculation of percent-buried-volume values for each quadrant around the metal center. KW - asymmetric catalysis KW - carbene ligands KW - helicenes KW - metathesis KW - ruthenium Y1 - 2018 U6 - https://doi.org/10.1002/chem.201802786 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 43 SP - 10994 EP - 10998 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schultze, Christiane A1 - Schmidt, Bernd T1 - Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins JF - Beilstein journal of organic chemistry N2 - 8-Allylcoumarins are conveniently accessible through a microwave-promoted tandem Claisen rearrangement/Wittig olefination/cyclization sequence. They serve as a versatile platform for the annellation of five- to seven-membered rings using ring-closing olefin metathesis (RCM). Furano-, pyrano-, oxepino- and azepinocoumarins were synthesized from the same set of precursors using Ru-catalyzed double bond isomerizations and RCM in a defined order. One class of products, pyrano[2,3-f]chromene-2,8-diones, were inaccessible through direct RCM of an acrylate, but became available from the analogous allyl ether via an assisted tandem catalytic RCM/allylic oxidation sequence. KW - coumarins KW - heterocycles KW - isomerization KW - olefin metathesis KW - ruthenium Y1 - 2018 U6 - https://doi.org/10.3762/bjoc.14.278 SN - 1860-5397 VL - 14 SP - 2991 EP - 2998 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, Main 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 - 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 - 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 - 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 - 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 - 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 - 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 -