New Method for Derivatization of Squaric Acid to Highly Substituted Cyclobutenones: Lewis Acid-Catalyzed Reaction of Cyclobutene-1,2-dione Monoacetal and Its Vinylog with Unsaturated Organosilanes, and Subsequent Ring Transformation of the Adducts
作者:Yoshihiko Yamamoto、Masatomi Ohno、Shoji Eguchi
DOI:10.1246/bcsj.69.1353
日期:1996.5
Described herein is a novel method for regio-controlled synthesis of highly substituted cyclobutenones having an unsaturated substituent at 4-position, starting from commercially available squaric acid. Both cyclobutene-1,2-dione monoacetal (4,4-diethoxycyclobutenone) and its vinylog (2,4-diethoxycyclobutenone), which were easily obtained from diethyl squarate, reacted with allylsilanes in the presence
本文描述了一种区域控制合成在 4 位具有不饱和取代基的高度取代的环丁烯酮的新方法,起始于可商购的方酸。环丁烯-1,2-二酮单缩醛(4,4-二乙氧基环丁烯酮)及其乙烯基(2,4-二乙氧基环丁烯酮)很容易从方酸二乙酯中获得,在 Et2O·BF3 存在下与烯丙基硅烷反应得到 4-烯丙基-4-乙氧基环丁烯酮在 2 位区域选择性地具有各种取代基。这些产物通过在二甲苯中回流有效地转化为高度取代的双环[3.2.0]庚烯酮。该方法的合成效用在三环系统的构建中得到了证明。使用丙二烯基硅烷、甲硅烷基烯醇醚进一步扩展路易斯酸催化的单缩醛反应,和甲硅烷基乙烯酮缩醛也提供相应的 4-取代产物。与上述 4-烯丙基化产物相比,4-炔丙基化和 4-酰基甲基化的 p...