Enantiomerically pure cis- and
trans-4-aminocyclohex-2-enols are prepared from
cyclohexa-1,3-diene via
(-)-cis-(1R,4S
)-4-acetoxycyclohex-2-enol (-)-2a using palladium(0)
chemistry. Benzylamine and diethylamine are tested in the
Pd0-catalysed allylic amination reactions. Since acetate is
too slow as a leaving group and gave considerable amounts of side
products, a number of leaving groups have been investigated. Of these
phosphinate and 2,4-dichlorobenzoate are excellent leaving groups and
result in efficient and highly stereoselective reactions; chloride as
allylic leaving group also gives good results. By variation of the
leaving group and proper choice of the protecting group it is possible
to synthesise all four stereoisomers of 4-aminocyclohex-2-enol in good
yield and high enantiomeric excess.
通过
钯(0)
化学方法,从环
己二烯-1,3出发,经(-)-顺-(1R,4S)-4-乙酰氧基
环己烯-2-醇(-)-2a,制备了手性纯的顺式和反式-4-
氨基
环己烯-2-醇。在
钯0催化的
烯丙基胺化反应中,测试了
苄胺和
二乙胺。由于
乙酸酯作为离去基团过于缓慢,并产生了大量副产物,因此研究了多种离去基团。其中,
膦酸酯和
2,4-二氯苯甲酸酯是优良的离去基团,能实现高效且高度立体选择性的反应;
氯作为烯丙基离去基团也取得了良好结果。通过变换离去基团并适当选择保护基团,可以高产率和高对映体过量地合成4-
氨基
环己烯-2-醇的全部四种立体异构体。