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Cyclization of 2‐methoxy‐6‐( substituted benzyloxy) acetophenone hydrazones in the presence of polyphosphoric acid (PPA)
Author(s) -
Qiu YuZhu,
Zhang Zheng,
Zhong ZkenQi,
Hu HongWen
Publication year - 1993
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.19930110407
Subject(s) - indazole , acetophenone , chemistry , hydrazone , medicinal chemistry , stereochemistry , organic chemistry , catalysis
Cyclization of 2‐methoxy‐6‐benzyloxy acetophenone hydrazone gave 3‐methyl‐4‐methoxy 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 hydrazone and 2‐hydroxy‐3‐benzyl‐6‐methoxy acetophenone hydrazone followed by cyclization to the corresponding indazoles in acidic conditions. Cyclization of 2‐methoxy‐6‐(halo or alky] 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 benzofuran and 3‐methy]‐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.