Addition of cyclopentadiene and 2-trimethylsilyloxyfuran to quinones bearing a menthyl ester chiral auxiliary
作者:Margaret A Brimble、Letecia J Duncalf、David C.W Reid、Tabitha R Roberts
DOI:10.1016/s0040-4020(98)00211-7
日期:1998.5
Addition of cyclopentadiene to 2-carbomethoxy-1,4-benzoquinone 9 afforded Diels-Alder adduct 10 using the Lewis acids ZnCl2 and ZnBr2 whereas the fragmenatation product 11 was the major product when using SnCl4 and TiCl4. Addition of cyclopentadiene to 1,4-benzoquinone 8 bearing a menthyl ester at C-2 afforded Diels-alder adduct 12 in moderate diastereomeric excess using ZnCl2 and ZnBr2 as Lewis acids
使用路易斯酸ZnCl 2和ZnBr 2将环戊二烯添加到2-羰基甲氧基-1,4-苯醌9中得到狄尔斯-阿尔德加合物10,而当使用SnCl 4和TiCl 4时,碎裂产物11是主要产物。将环戊二烯加至在C-2处带有薄荷基酯的1,4-苯醌8中,使用ZnCl 2和ZnBr 2作为路易斯酸,以适度的非对映体过量得到狄尔斯-阿尔德加合物12。使用TiCl 4和SnCl 4得到碎裂产物13也有中等非对映异构体过量。向手性萘醌4和苯醌8中加入2-三甲基甲硅烷基氧基呋喃,分别得到非对映异构体1:1混合物的呋喃呋喃加合物14和15。