Treatment of 4-hydroxy-2,2-diphenyl-3-pentenoic acid lactone (3) with phenyllithium gives 1,2,2-triphenyl-1,4-pentanedione (2), 1,3,3-triphenyl-1,4-pentanedione (7), and 3,3-diphenylpropiophenone (16). The γ-diketone 7 is shown to arise via rearrangement of an anion of the γ-diketone 2. The formation of 1,2,3-triphenyl-1,4-pentanedione (27) is not observed, nor is 27 converted to 7 on treatment with base. It is concluded that the rearrangement proceeds via two homoenolate anion intermediates rather than via two 1,2 phenyl shifts.
用
苯基锂处理
4-羟基-2,2
-二苯基-3-戊烯酸内酯(3)会得到1,2,2-三苯基-1,4-
戊二酮(2)、1,3,3-三苯基-1,4-
戊二酮(7)和3,3-二
苯基丙酮(16)。γ-二酮7的形成是通过γ-二酮2的负离子重排产生的。未观察到1,2,3-三苯基-1,4-
戊二酮(27)的形成,27在碱处理时也没有转化为7。结论是重排是通过两个同型烯醇负离子中间体进行,而不是通过两个1,2苯移位进行。