共查询到20条相似文献,搜索用时 55 毫秒
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Christopher Cooze Raphael Dada Rylan J. Lundgren 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12374-12379
Methods for the addition of unsaturated nucleophiles to carbonyls to generate Z‐olefin products remain rare and often require either alkyl borane or zinc reductants, limiting their utility. Demonstrated here is that formic acid mediates the Rh‐catalyzed, Z‐selective coupling of dienes and aldehydes. The process is distinguished by broad tolerance towards reducible or electrophilic groups. Kinetic analysis suggests that generation of the catalytically active Rh intermediate by ligand dissociation is the rate‐determining step. The rapid generation and trapping of Rh‐allyl intermediates is key to preventing chain‐walking isomerization events that plague related protocols. Insights gained through this study may have wider implications in selective metal‐catalyzed hydrofunctionalization reactions. 相似文献
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Barry M. Trost Johnathan E. Schultz Yu Bai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11946-11951
We describe the development of a Pd‐catalyzed decarboxylative asymmetric allylic alkylation of α‐nitro allyl esters to afford acyclic tetrasubstituted nitroalkanes. Optimization of the reaction parameters revealed unique ligand and solvent combinations crucial for achieving chemo‐ and enantioselective C‐alkylation of electronically challenging benzylic nitronates and sterically encumbered 2‐allyl esters. Substrates were efficiently accessed in a combinatorial fashion by a cross‐Claisen/ α‐arylation sequence. The method provides functional group orthogonality that complements nucleophilic imine allylation strategies for α‐tertiary amine synthesis. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(30):8906-8910
We describe the synthetically useful enantioselective addition of Br−CX3 (X=Cl or Br) to terminal olefins to introduce a trihalomethyl group and generate optically active secondary bromides. Computational and experimental evidence supports an asymmetric atom‐transfer radical addition (ATRA) mechanism in which the stereodetermining step involves outer‐sphere bromine abstraction from a [(bisphosphine)RhIIBrCl] complex by a benzylic radical intermediate. This mechanism appears unprecedented in asymmetric catalysis. 相似文献
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Charles Romain Charlotte K. Williams 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(6):1633-1636
A novel chemoselective polymerization control yields predictable (co)polymer compositions from a mixture of monomers. Using a dizinc catalyst and a mixture of caprolactone, cyclohexene oxide, and carbon dioxide enables the selective preparation of either polyesters or polycarbonates or copoly(ester‐carbonates). The selectivity depends on the nature of the zinc–oxygen functionality at the growing polymer chain end, and can be controlled by the addition of exogeneous switch reagents. 相似文献
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