Phosphine-directed stereo- & regioselective Ni-catalyzed reactions of Grignard reagents with allylic ethers
作者:Mary T. Didiuk、James P. Morken、Amir H. Hoveyda
DOI:10.1016/s0040-4020(97)10212-5
日期:1998.2
Studies on the directed regio- and stereoselective Ni-catalyzed allylic substitution reactions involving methyl- and phenylmagnesium bromides and various acyclic and cyclic allylicethers are reported. In the presence of a properly positioned internal Lewis base, CC bonds can be formed catalytically and with excellent levels of selectivity. Internal chelation allows Ni-catalyzed CC bond forming reactions
Ring Opening of Cyclic Vinylogous Acyl Triflates Using Stabilized Carbanion Nucleophiles: Claisen Condensation Linked to Carbon−Carbon Bond Cleavage
作者:David M. Jones、Marilda P. Lisboa、Shin Kamijo、Gregory B. Dudley
DOI:10.1021/jo100249g
日期:2010.5.21
Addition of stabilized carbanionic nucleophiles to cyclic vinylogous acyl triflates (VATs) triggers a ring-opening fragmentation to give acyclic β-keto ester and related products, much like those observed traditionally in the Claisen condensation. Unlike in the classical Claisen condensation, however, the VAT-Claisen reaction described herein is rendered irreversible by C−C bond cleavage, not by deprotonation
Ethyl 2-benzyloxy-3,3-difluoropropenoate as a novel synthon of β-fluoro-α-keto acid derivatives, preparation and reactions with nucleophiles
作者:Guo-qiang Shi、Zhi-yao Cao
DOI:10.1039/c39950001969
日期:——
Ethyl 2-benzyloxy-3,3-difluoropropenoate 3, prepared from the readily obtainable ethyl trifluoropyruvate, reacts with a variety of nucleophiles to give β-fluoro-α-keto acid derivatives in high yield.
Novel 1,4-asymmetric induction in nucleophilic 1,2-additions to chiral γ-amino enals
作者:M. T. Reetz、Fan Wang、K. Harms
DOI:10.1039/c39910001309
日期:——
γ-Dibenzylamino enals 3a with the E-configuration derived from amino acids 1 react diastereoselectively with cuprates in an unexpected 1,2-manner, while the analogues 3b with the Z-configuration undergo diastereoselective additions with organolithium reagents.
depending upon the reaction conditions and the reactivity of donor molecules. The adduct anions, both 1:1 and 1:2 types, are quenched with alkyl halides or water in a highly stereoselective manner to produce α-silylated esters. A rigid intramolecular chelation working in the adduct anions is partly responsible for the high selectivity.