Cyclization of 2-methoxy-6-(substituted benzyloxy)acetophenone hydrazones in the presence of polyphosphoric acid(PPA)

Cyclization of 2-methoxy-6-benzyloxy acetophenone hydrazone gave 3-methyl-4-meth- oxy indazole and 3-methyl-4-methoxy-7-benzyl indazole in the presence of polyphosphoric acid (PPA).The hydrazone was probably converted to 2-hydroxy-6-methoxy acetophenone hydra- zone and 2-hydroxy-3-benzyl-6-methoxy acetophenone hydrazone followed by cyclization to the corresponding indazoles in acidic conditions.Cyelization of 2-methoxy-6-(halo or alkyl or aryl benzyloxy)acetophenone hydrazones gave similar products.Cyclization of 2-methoxy-6- (p-nitrobenzyloxy)acetophenone hydrazone gave 2-(p-nitrophenyl)-3-methyl-4-methoxy benzo- furan and 3-methyl-4-methoxy indazole while 2-methoxy-6-(m-nitrobenzyloxy)acetophenone hydrazone gave 3-methyl-4-methoxy indazole,3-methyl-4-methoxy-7-(m-nitrophenyl)indazole and 3-methyl-4-(m-nitrobenzyloxy)indazole.

2,6-二烷氧基(羟基)苯乙酮的苄腙和甲腙合成吲唑类化合物

在多聚磷酸存在下，２，４６－二烷氧基苯乙酮的苄腙和甲腙可以发生环化反应，生成产率较高的吲唑类化合物。根据实验结果，我们推测反应的关键步骤为关核进攻，化合物的结构均经元素分析，ＩＲ，＾１Ｈ ＮＭＲ和ＭＳ确定。