Transmetalation of C-5-lithiomethylisoxazoles with the lower-order cuprate reagent lithium thienylcyanocuprate (Li[ThCuCN]) in THF results in exclusive conjugate addition to α,β-unsaturated carbonyls. In contrast, transmetalation with samarium tris(hexamethyldisilazide) (Sm[HMDS]3) in diethyl ether directs 1,2-carbonyl addition. In both cases, optimum results were realized with a 4,5-dihydro-4,4-dimethyl-Π2-oxazoline substituent at the C-4 position of the isoxazole.
用低阶
铜氧化物试剂
噻吩基
氰基杯酸
锂(Li[ThCuCN])在
四氢呋喃中对 C-5-lithiomethylisoxazoles 进行反
金属反应,可使其与δ、δ²-不饱和羰基发生共轭加成反应。相反,在二
乙醚中用三(六甲基二
硅氮化物)
钐(Sm[
HMDS]3)进行反
金属化则可直接进行 1,2-羰基加成。在这两种情况下,
异噁唑 C-4 位上的 4,5-二氢-4,4-二甲基-δ 2-
噁唑啉取代基都能产生最佳结果。