The oxidation of monoalkyl 2-(9H-xanthenyl)malonates 1 with Mn(OAc)3 gave the 9- or 10-dibenz[b,f]oxepincarboxylates 2 in good yields. The reaction proceeds with high regioselectivity except for the case of (1-methoxyxanthenyl)malonate 1 (R1 = Me, R2 = 1-MeO), which gave two regioisomers. It was proposed that the process for the formation of 2 must include the 1,2-aryl radical rearrangement followed
用Mn(
OAc)3
氧化2-(9 H-
黄嘌呤基)
丙二酸单烷基
酯1可获得高产率的9-或10-二
苯并[ b,f ]
氧苯哌酸酯2。除了(1-甲
氧基黄
蒽基)
丙二酸酯1(R 1= Me,R 2= 1-MeO)的情况以外,该反应以高区域选择性进行,其给出两种区域异构体。提出形成2的方法必须包括1,2-芳基自由基重排,然后进行
氧化
脱羧。