Rearrangements of the Diels−Alder Cycloadducts Obtained from Acetylenic Sulfones and 1,3-Diphenylisobenzofuran
作者:Thomas G. Back、Masood Parvez、Huimin Zhai
DOI:10.1021/jo060598e
日期:2006.7.1
products underwent various types of rearrangements under pyrolytic, acid-catalyzed, and photochemical conditions. In the presence of acid, or upon heating in xylenes, they afforded the ketones 5a,b. In addition, the dehydration product 7a was produced from the pyrolysis of 4a, and the unexpected transposed ketone 6b was generated under acid-catalyzed or pyrolytic conditions from 4b via a postulated
1,3-二苯基异苯并呋喃分别提供具有正丁基和苯基取代的炔属砜3a,b的Diels-Alder环加合物4a,b。产品在热解,酸催化和光化学条件下经历了各种类型的重排。在酸的存在下,或在二甲苯中加热时,它们提供了酮5a,b。另外,由4a的热解产生脱水产物7a,并且在酸催化或热解条件下由4b产生意外的转位酮6b。通过假定的环氧中间体。4a的光解得到酮5a作为唯一的分离产物,而5b则得到oxepin 8b和茚基苯基酮9b。后两种产物的形成可以通过一系列周环反应来合理化。这些包括分子内[2 + 2]环加成反应,然后进行1,3偶极环还原,以将4b转化为8b,以及一系列将8b转化为9b的电环和[1,3]σ反应。