Chiral tertiary dichloromethylcarbinol derivatives 2, prepared from protected chiral secondary alcohols 1, were converted stereospecifically into chiral quaternary α-oxygenated aldehyde derivatives 4 and 11 via intermediary α-chloroepoxides 3 under weakly basic conditions (K 2 CO 3 /ΜeOH/r.t.). The fashion generating the quaternary centers was proved to be quite different depending on the substrates:
由受保护的手性仲醇1制备的手性叔二氯甲基甲醇衍生物2在弱碱性条件(K 2 CO 3 /MeOH/rt)下经由中间α-氯环氧化物3立体定向地转化为手性季α-氧化醛衍生物4和11。证明生成四元中心的方式因底物而异:非苄基底物 2a 的构型反转和苄基底物 2b 的表观保留。
A Simple Primary Amine Catalyst for Enantioselective α-Hydroxylations and α-Fluorinations of Branched Aldehydes
作者:Michael R. Witten、Eric N. Jacobsen
DOI:10.1021/acs.orglett.5b01193
日期:2015.6.5
A new primary amine catalyst for the asymmetric a-hydroxylation and a-fluorination of alpha-branched aldehydes is described. The products of the title transformations are generated in excellent yields with high enantioselectivities. Both processes can be performed within short reaction times and on gram scale. The similarity in results obtained in both reactions, combined with computational evidence, implies a common basis for stereoinduction and the possibility of a general catalytic mechanism for a-functionalizations. Promising initial results in alpha-amination and alpha-chlorination reactions support this hypothesis.
PAULMIER, CLAUDE;OUTURQUIN, FRANCIS;PLAQUEVENT, JEAN-CHRISTOPHE, TETRAHEDRON LETT., 29,(1988) N 46, C. 5889-5892