作者:Angela M. Celli、Mirella Scotton、Alessandro Sega
DOI:10.1016/s0040-4020(01)90180-2
日期:1992.7
The hetero-Diels-Alder reaction of 1-oxabutadienes 1a–c bearing electron-withdrawing groups with ethyl vinyl ether and 2,3-dihydrofuran gave the functionalized 5,6-dihydro-4H-pyrans 2a-c, 4c and 4H-4a, 5, 6, 6a-tetrahydrofuro[2,3-b]pyrans 5a-c and 6c. Cycloadducts 2a and 4c easily rearranged to furo[2,3-b]furans 3a, 3c and 9c and cycloadducts 5a and 6c to difuro[2,3-b:3′,4′-d]furans 7a, 7c and 8c.
带有吸电子基团的1-氧杂硼二烯1a-c与乙基乙烯基醚和2,3-二氢呋喃的杂Diels-Alder反应得到官能化的5,6-二氢-4H-吡喃2a-c,4c和4H-4a ,5、6、6a-四氢呋喃[2,3-b]吡喃5a-c和6c。环加合物2a和4c容易地重排为呋喃[2,3-b]呋喃3a,3c和9c,环加合物5a和6c重排为呋喃[2,3-b :3′,4′-d]呋喃7a,7c和8c。化合物5c的立体化学和图7a是通过单晶X-射线分析测定。通过nOe数据确定了其他化合物的相对构型。讨论了反应机理的一些方面。