由醇6a-c和12a,b分别分两步制备在三元环或亚甲基环丙烷或双环亚丙基部分的双键上具有炔基取代基的三甲基甲硅烷基保护的炔烃9a-c和14a,b通过转化为碘化物并与(三甲基甲硅烷基)乙炔化锂(8)偶联,总产率为38-73%。通过锂化,然后与(5-碘戊-1-炔基)三甲基硅烷(11)偶合,直接从双环亚丙基(3)以49%的收率合成双环亚丙基衍生物9d。通过用甲醇中的K 2 CO 3处理使烯炔9b-d被蛋白去甲硅烷基化,分别以53、74和94%的产率得到相应的未保护的烯炔10b-d。通过维蒂希烯化反应由羰基衍生物15a-c合成具有与炔基部分相邻的羰基的烯炔17a-c,然后分别以8、47、18和12%的总收率偶联8。亚甲基环丙烷衍生物在环(9a,b和10a)以及双键(14a,b及其原位制备的丙二甲硅烷基化的类似物)上具有取代基的Pauson-Khand反应通过搅拌相应的烯炔与[ Co2(CO)8]在
Intramolecular Diels-Alder reactions of furans with a merely strain-activated tetrasubstituted alkene: Bicyclopropylidene
作者:Thomas Heiner、Sergei I. Kozhushkov、Mathias Noltemeyer、Thomas Haumann、Roland Boese、Armin de Meijere
DOI:10.1016/0040-4020(96)00720-x
日期:1996.9
Bicyclopropylidene derivatives 1, 6, 8 with furan moieties attached on tethers of various length and nature all undergo clean intramolecular Diels-Alder reactions with complete endo-diastereoselectivities when heated to 70 - 130 degrees C, under 10 kbar pressure. The reaction rates are at]east as high or higher than those of analogously tethered methylenecyclopropane-furan derivatives 15, 17, 20, in spite of the fact that the reactive double bond in bicyclopropylidene is tetrasubstituted and not activated by any electron withdrawing group. Copyright (C) 1996 Elsevier Science Ltd