Stereoselective Synthesis of Highly Functionalized Trisubstituted Olefins via the Aldol Reaction of Allenoxyborinates with Carbonyl Compounds
摘要:
Allenoxyborinates, generated via the reaction of dicyclohexylborane with alpha,beta-acetylenic ketones, react in situ with excess starting ketone to afford stereodefined, functionalized, trisubstituted olefins in good yields. The allenoxyborinates, (RCH=C=C(R')OB(c-C6H11)(2), can also be trapped by aldehydes and ketones when R' is a tert-butyl group.
Decarboxylative Negishi Coupling of Redox‐Active Aliphatic Esters by Cobalt Catalysis
作者:Xu‐Ge Liu、Chu‐Jun Zhou、E. Lin、Xiang‐Lei Han、Shang‐Shi Zhang、Qingjiang Li、Honggen Wang
DOI:10.1002/anie.201806799
日期:2018.10
A cobalt‐catalyzed decarboxylative Negishi coupling reaction of redox‐active aliphatic esters with organozinc reagents was developed. The method enabled efficient alkyl–aryl, alkyl–alkenyl, and alkyl–alkynyl coupling reactions under mild reaction conditions with no external ligand or additive needed. The success of an in situ activation protocol and the facile synthesis of the drug molecule (±)‐preclamol
Three‐Component Difunctionalization of Cyclohexenyl Triflates: Direct Access to Versatile Cyclohexenes via Cyclohexynes
作者:Seoyoung Cho、E. J. McLaren、Qiu Wang
DOI:10.1002/anie.202109482
日期:2021.12.6
dicarbofunctionalization, aminohalogenation and aminocarbonation of readily available cyclohexenyl triflates, via strained cyclic alkyne intermediates generated in situ. The importance and utility of this method is exemplified by the modularity of this approach and the ease in which even highly complex polycyclic scaffolds can be accessed in one step.
Alkynylzinc reagents were found to undergo coupling with aryl and alkenyl iodides to give arylalkynes and alkenylalkynes with no aid of transition metals. The coupling reaction proceeds through a single...
and proton sponge in toluene, terminalalkynes were found to undergo the alkylation by alkyl triflates to provide unsymmetrical internal alkynes. This is the first example that a simple alkyl chain other than benzylic and norbornyl units can be introduced onto the alkynyl carbon atom under Lewis acid catalysis. Mechanisticstudies revealed that the activation of the alkyne by the zinc Lewis acid and proton
cis‐pyridinium‐type salts. These salts reacted with variousnucleophiles, such as alcohols, azides, and organozinc reagents, to form nucleophilic‐substitution products. A characteristic feature of these processes was that they took place under mild conditions, which did not affect acid‐labile protecting groups. Furthermore, the reactions that employed azides and C‐nucleophiles generated 2,6‐trans products with high