Preparation and Intramolecular [2+2]-Photocycloaddition of 1,5-Dihydropyrrol-2-ones and 5,6-Dihydro-1<i>H</i>-pyridin-2-ones with C-, N-, and O-linked Alkenyl Side Chains at the 4-Position
作者:Dominik Albrecht、Birte Basler、Thorsten Bach
DOI:10.1021/jo7027129
日期:2008.3.1
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(-)-