Stereoselective SN2′ alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturated ester system via γ,δ-chlorohydrin intermediates by the use of a R3Al–CuCN reagent
A novel stereoselective SN2′ alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturatedester system has been developed which involves a regioselective substitution reaction with chloride ions at the γ-position and a subsequent SN2′ alkylation reaction of the resulting γ-chloro-δ-hydroxy derivatives with a R3Al–CuCN reagent. The new methodology was demonstrated to be applicable to a variety of substrates
已经开发了γ,δ-环氧α,β-不饱和酯系统的新型立体选择性S N 2'烷基化反应序列,其涉及在γ-位与氯离子的区域选择性取代反应和随后的S N 2'烷基化反应R 3 Al–CuCN试剂合成的γ-氯代-δ-羟基衍生物。事实证明,该新方法可适用于多种底物,并提供各种δ-羟基-α-烷基-β,γ-不饱和酯,包括以高度立体选择性的方式在α-位带有季不对称碳原子的那些酯,以及高产。
Regio- and stereo-selectivity in the reaction of methyl 4,5-epoxy-2-hexenoate with methylcopper reagents
The reaction of 4,5-epoxy-2-hexenoate (3) with methylcopper, dimethylcuprate, and their BF3, complexes gave predominantly the γ-methylated product (5) via SN2 process, while the reaction with methylcyanocuprate, higher order dimethylcyanocuprate and their BF3 complexes afforded preferentially the α-methylated product (4) via SN2 ' process. Anti-diastereoselectivity was observed regardless of the substitution
4,5-环氧-2-己烯酸酯(3)与甲基铜,二甲基铜酸酯及其BF 3配合物的反应主要通过S N 2过程得到的γ-甲基化产物(5),而与甲基氰脲酸酯的反应则更高级通过S N 2'方法,优先得到二甲基氰基丙二酸酯及其BF 3络合物,得到α-甲基化产物(4)。无论取代模式如何,均观察到抗非对映选择性。BF 3 ·OEt 2的存在降低了抗选择性,在某些情况下,在BF 3 ·OEt过量的情况下观察到相反的同-非对映选择性2。在CNDO / 2计算的基础上讨论了这些区域选择性和立体选择性。
Epoxy-silanes in organic synthesis
作者:Garry Procter、Andrew T. Russell、Patrick J. Murphy、T.S. Tan、Andrew N. Mather
DOI:10.1016/s0040-4020(01)86648-5
日期:1988.1
Palladium-catalyzed reactions of alkenyloxiranes with carbon monoxide
Reaction of alkenyloxiranes with carbon monoxide in the presence of palladium catalysts gives unsaturated esters, beta-lactones, dienes, and allylic alcohols. The selectivity of the reaction depends on the nature of the alkenyloxiranes. Carbonylation products were obtained in the reaction of terminal alkenyloxiranes and alkenyloxiranes having electron-donating substituents, whereas carbonylation scarcely took place in the reaction of alkenyloxiranes having electron-withdrawing groups; dienes and allylic alcohols were produced instead of carbonylation products.
OTSUBO, KENJI;INANAGA, JUNJI;YAMAGUCHI, MASARU, TETRAHEDRON LETT., 28,(1987) N 38, 4437-4440