Stereoselective addition of R2CuLi to ortho-substituted methyl cinnamates intramolecular assistance and solvent effects

Total Synthesis of (−)‐Indoxamycins A and B

“…Thed esired product was obtained in very low yield when THF was used as solvent. [11] Subsequently,t reatment of 14 with p-TsOH [12] resulted in complete isomerization of ad ouble-substituted olefin to am ore stable tetra-substituted one,w hich was subjected to ozonolysis to yield aketone 15 in 67 %yield. Simultaneously, the ketal stereogenic center at the C2 position isomerized to give as ingle diastereoisomer under such acidic conditions.…”

Stereoselective Conjugate Addition Reactions of α,β-Unsaturated tert-Butyl Esters with Aryllithium Reagents

“…This structural element is present in compounds which have reported activities as antiarrhythmics, , vasodilators (Ca-modulin antagonists), , antidepressives, ,, antihistamines, and controllers of cerebral insufficiency . As such, synthetic methods are required for the preparation of a wide variety of compounds of this general structure, ,,,− especially in an optically pure form. ,− In this regard we were attracted to methodology developed by Alexakis involving stereoselective 1,4-addition of lithium diphenyl cuprate to α,β-unsaturated ethyl ester 1 possessing a neighboring chiral controller (chiral imidazolidine) …”

Fluorine-Retentive Strategies for the Functionalization of gem-Difluoroalkenes

“…29 The increase in stereoselectivity observed with Cu can be explained by the competitive coordination of the lithium cuprate with solvent, which disfavors coordination with the epoxide. 30 Oxirane-bearing gem-difluoroalkenes can also be regio-and stereoselectively reduced to give gem-difluoromethyl-containing products using DIBAL-H (E-selective) and BH3•THF (Z-selective; Scheme 5F,G). 26,28 The Z-selective isomer is derived from the chair-like sixmembered transition state with the smaller BH3 (36; Scheme 5G).…”