Conformationally constrained 2-methylidene 1,3-oxathiane S-oxides: synthesis and nucleophilic additions
作者:Daniel Weingand、Claude Kiefer、Joachim Podlech
DOI:10.1016/j.tet.2014.12.098
日期:2015.2
substrates were prepared by oxidation of 2-hydroxymethyl-1,3-oxathianes and pyrolysis of the respective xanthogenates. Nucleophilic additions of ethyl thiolate, piperidine, and dimethyl malonate anion are over 100 times faster to axial sulfoxides than to the respective equatorial substrates. The oxathiane derivatives turned out to be about 1000 times less reactive than the respective 1,3-dithianes.
乙烯基亚砜的性质受到立体电子效应的显着影响,其中亚砜基和烯烃部分的相对取向决定了反应性和选择性,例如,添加了亲核试剂。2-亚甲基1,3-氧杂亚砜S-氧化物的构象受约束的衍生物可以量化立体电子效应。通过氧化2-羟甲基-1,3-氧杂蒽并热解相应的黄原酸酯来制备合适的底物。硫代乙酸乙酯,哌啶和丙二酸二甲酯阴离子的亲核性加成对轴向亚砜的速度比对相应的赤道底物快100倍以上。氧杂蒽衍生物的反应性比相应的1,3-二硫杂环丁烷低约1000倍。