钯催化脱芳构/异构化一锅合成β-甲基苯乙烯

Palladium-catalyzed dearomatization/isomerization of one-pot synthesis of β-methylstyrene

本文使用苄氯及其衍生物和烯丙基三正丁基锡作为底物,通过钯催化的串联脱芳构化/烯烃异构化策略一锅法合成了一系列β-甲基苯乙烯类化合物.结果表明:以双二亚苄基丙酮钯(Pd2(dba)3,反应物物质的量的5%)为催化剂,三苯基膦(PPh3,反应物物质的量的10%)为配体,二氯甲烷为溶剂,室温下反应12h后,再用对甲基苯磺酸酸化,高收率和高选择性地得到一系列反式β-甲基苯乙烯类化合物,产率在60%~84%之间.该反应条件温和,底物适用性广,官能团兼容性较好,如带有甲基、甲氧基、氰基、卤原子、酯基等基团的苄氯衍生物均可适用该反应.

The synthesis ofβ-methylstyrenes is of general interest because this motif is present in many natural products,and is widely used in the construction of intermediates for complex products.In this paper,a series ofβ-methylstyrene compounds were synthesized by one-pot method using benzyl chloride and its derivatives with allyl tributyltin as substrate via palladium-catalyzed tandem dearomatization/isomerization.Therefore,the reaction of benzyl chloride and allyl tributyltin were performed in the presence of Pd2(dba)3,PPh3,using DCM as solvent at room temperature for 24 h.A series of trans-β-methylstyrene compounds were obtained by acidification with p-toluenesulfonic acid with high yield and high selectivity.The yield was between 60%~84%.This new type of reaction is operationally simple and exhibits high functional-group tolerance.Various synthetically useful functional groups,such as methyl group,methoxy group,cyano group,halogen atom or ester group remain intact during reaction ofβ-methylstyrenes.