Synthesis of monoprotected 1,4-diketones by photoinduced alkylation of enones with 2-substituted-1,3-dioxolanes
作者:Raffaella Mosca、Maurizio Fagnoni、Mariella Mella、Angelo Albini
DOI:10.1016/s0040-4020(01)01058-4
日期:2001.12
Photosensitized hydrogen abstraction from 2-alkyl-1,3-dioxolanes by triplet benzophenone gives the corresponding 1,3-dioxolan-2-yl radicals and these are trapped by α,β-unsatured ketones yielding monoprotected 1,4-diketones. With open chain ketones (3-buten-2-one and 4-penten-3-one) the yields are low and competitive pathways in part consume the radicals. With cyclic enones however, yields are good
三联体二苯甲酮从2-烷基-1,3-二氧戊环光敏化氢原子得到相应的1,3-二氧戊环-2-基,这些基团被α,β-不饱和酮捕获,生成单保护的1,4-二酮。使用开链酮(3-丁烯-2-酮和4-戊烯-3-酮),收率低,竞争途径部分消耗了自由基。然而,使用环烯酮,如用环戊烯酮,环己烯酮和4-羟基-环戊烯酮所测试的那样,产率是好的。更一般地,这是通过自由基合成1,4-二酮的可行替代方案,而热引发仅产生低产率。该反应不能扩展到高度稳定的基团,例如2-苯基-1,3-二氧戊环基。