Dienophilic thioaldehydes and dithioesters formed by base-catalysed cleavage of alkyl phthalimidosulfanylacetates
作者:Gordon W. Kirby、Alistair W. Lochead、Sharon Williamson
DOI:10.1039/p19960000977
日期:——
Treatment of ethyl and methyl phthalimidosulfanylacetate 1a and 1b with triethylamine at room temperature generates [eqn. (1)] the transient thioaldehydes, ethyl and methyl thioxoacetate 2, which have been trapped in situ with 2,3-dimethylbuta-1,3-diene to yield the Diels–Alder cycloadducts 8a and 8b in high yield. The cycloadducts 9, 10 and 11a and 12a of ethyl thioxoacetate 2a and anthracene, cyclohexa-1
在室温下用三乙胺处理乙基和亚甲基邻苯二甲硫基乙酸乙酸乙酯1a和1b产生[eqn。(1)]瞬态硫醛,乙基和甲基硫代乙酸甲酯2,已用2,3-二甲基-1,3-二烯就地捕获,从而以高收率生产了Diels-Alder环加合物8a和8b。类似地,分别获得了硫代氧乙酸乙酯2a和蒽,环己-1,3-二烯和环戊二烯的环加合物9、10和11a和12a。以endo :exo = 7:3的比例形成的环戊二烯的endo -11a和exo -12a环加合物,在甲苯中加热回流时可逆分解,得到相同的平衡混合物,endo:exo= 3∶7,因此可以切断作为硫代乙酸乙酯2a的“清洁”辅助前体。因此,当环加合物11a和12a的混合物依次与二甲基丁二烯和(E,E)-1,4-二苯基丁-1,3-二烯,得到相应的二烯环加合物8a和13。出乎意料的是,在二甲基丁二烯存在下,用三乙胺(1摩尔当量)和4-二甲基氨基吡啶(DMAP)(0.1摩尔