A NEW PROTOCOL FOR REGIOCONTROLLED AND STEREOCONTROLLED ALDOL REACTIONS THROUGH THE CONJUGATE ADDITION OF DIALKYLBORANES TO ALPHA,BETA-UNSATURATED KETONES

被引：43

作者：

BOLDRINI, GP ^{[1
]}

BORTOLOTTI, M ^{[1
]}

MANCINI, F ^{[1
]}

TAGLIAVINI, E ^{[1
]}

TROMBINI, C ^{[1
]}

UMANIRONCHI, A ^{[1
]}

机构：

[1] UNIV BOLOGNA,DIPARTIMENTO CHIM G CIAMICIAN,VIA SELMI 2,I-40126 BOLOGNA,ITALY

来源：

JOURNAL OF ORGANIC CHEMISTRY | 1991年 / 56卷 / 20期

关键词：

D O I：

10.1021/jo00020a025

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

A one-pot, two-step procedure, consisting of the 1,4-addition of dialkylboranes to beta-substituted (E)-alpha,beta-unsaturated ketones followed by the reaction of the resulting configurationally pure (Z)-(vinyloxy)boranes with aldehydes, is reported. The overall process corresponds to a regio- and stereocontrolled aldol addition of an unsymmetrical ketone to an aldehyde. A concerted 1,4-addition mechanism accounts for the stereochemical outcome of the hydroboraton reaction; cyclic enones do not undergo conjugate addition, while (Z)-beta-substituted or beta,beta-disubstituted alpha,beta-unsaturated ketones still react in a 1,4-fashion, but with a slower rate and a lower degree of chemoselectivity with respect to beta-substituted (E)-alpha,beta-unsaturated ketones. In the cases of alpha,beta-disubstituted alpha,beta-unsaturated ketones and (E)-(S-phenylthio)cinnammate, which react with dicyclohexylborane to give a mixture of E and Z enolates, an alternative mechanism is proposed.

引用

页码：5820 / 5826

页数：7

共 37 条

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