2-(trimethylsiloxy)furan (4) to the 1,4-benzoquinones (5a–e) containing electron-withdrawing groups at C-2 gave the cis-3a,8b-dihydrofuro[3,2-b]benzofuran-2(3H)-ones (6a–e) in 51–76% yields. The 1,4-benzoquinones (5f, g, h) without electron-withdrawing groups at C-2 failed to undergo the furofuran annulation, with none of the desired adducts (6f, g, h) being isolated. The carboxylic acid adduct (6i; R = CO2H) was
                                    将未催化的2-(三甲基甲
硅烷氧基)
呋喃(4)加至在C-2处具有吸电子基团的1,4-苯醌(5a - e)得到顺式-3a,8b-二氢
呋喃[3,2- b ]
苯并呋喃2(3 H)-ones (6a – e)的产率为51–76%。在C-2处没有吸电子基团的1,4-苯醌(5f,g,h)不能进行
呋喃呋喃环化,没有分离出任何所需的加合物(6f,g,h)。
羧酸加合物(6i ; R = CO 2H)是通过在
乙酸中使用
锌将苯甲酰加合物(6e)或三
氯乙基酯加合物(6d)还原
水解而间接制备的。用酸处理甲基酮加合物(6b)使相应的(
苯并呋喃-2-基)
乙酸(9)开环。