Formation and [4 + 2] cycloaddition reactions of 2,3-dimethylene-2,3-dihydrothiophene
作者:Keimpe J. van den Berg、Albert M. van Leusen
DOI:10.1002/recl.19931120103
日期:——
2,3-Dimethylene-2,3-dihydrothiophene (1), the thiophene analog of o-xylylene (o-quinodimethane), was generated in situ from the (trialkylammoniomethyl)-(trimethylsilylmethyl)thiophene iodides 4 or 5 by fluoride-induced 1,4 climination, and was trapped by [4 + 2] cycloadditions with a series of dienophiles. The reaction of 1 with dimethyl fumarate was considerably faster than with dimethyl maleate.
2,3-二亚甲基-2,3-二氢噻吩(1)是邻二甲苯(邻喹二甲烷)的噻吩类似物,是由(三烷基铵甲基)-(三甲基甲硅烷基甲基)噻吩碘化物通过氟化物原位生成的1,4气候,并被一系列亲二烯体[4 + 2]环加成法捕获。1与富马酸二甲酯的反应比与马来酸二甲酯的反应快得多。不对称的亲双烯体产生区域异构体的混合物。在不存在亲双烯体的情况下,通过1 H-NMR与15a的四氘代类似物的比较确定,其中1个形成了[4 + 2]个螺二聚体,其中15a是主要成分。1和Dideutero- 1的新前体的合成:描述了化合物4、5a,b以及4的3.4-异构体。