ion include the use of dichloromethane as the solvent and an irradiation with a mercury low-pressure lamp (λ = 254 nm). Upon applying these conditions at ambient temperature, the corresponding intramolecular photocycloaddition products 28−37 were obtained in good yields (52−79%) and with perfect diastereoselectivity. The constitution and configuration of the products was elucidated by NMR-spectroscopy
1,5-二氢
吡咯-2-酮2,6,9,和11(从甲基tetramates制备1A - Ç),Ñ -Boc保护的特特拉姆酸(3),或ñ -Boc保护的特特拉姆酸
溴化物(7)以短的反应顺序和非常好的总产率。同源5,6-二氢-1- ħ -
吡啶-2-酮16,18,20,21,23,和27分别沿着从
哌啶-2,4-二酮起始类似途径制备(19),或者从它的ñ -叔丁基衍
生物15。[2 + 2]-光环加成反应的最佳条件包括使用
二氯甲烷作为溶剂和用
汞低压灯(λ= 254 nm)照射。当在环境温度下施加这些条件下,相应的分子内光环产品28 - 37以良好的收率(52-79%)中,用非对映选择性完美得到。通过NMR光谱阐明了产物的组成和构型。对于O系衬底2a和20,观察到光环加成率随温度强烈降低。的效果不太明显了N-和C-拴基板6,9,23,和27。使用手性络合剂实现对映选择性反应似乎是可行的。然而,络合剂(-)-