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Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8′‐methylene‐bis‐4‐oxo‐1 H and 2 H ‐chromeno[4,3‐ C ]pyrazoles
Author(s) -
Nagaraj Adki,
Reddy Cherkupally Sanjeeva
Publication year - 2007
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570440619
Subject(s) - methylene , chemistry , regioselectivity , salicylic acid , microwave irradiation , organic chemistry , catalysis , biochemistry
AbstractThe ethyl ester of 5,5′‐methylene‐bis‐salicyclic acid 3 was prepared by the esterification of 5,5′‐methylene‐bis‐salicylic acid 2 . The compound 3 on reacting with ethylacetoacetate yields 6,6′‐methylenebis‐(3‐acetyl‐4‐hydroxycoumarin) 4 . The compound 4 was regioselectively converted into either 8,8′‐methylene‐bis‐(4‐oxo‐1 H ‐chromeno[4,3‐ c ]pyrazoles) 6 or 8,8′‐methylene‐bis(‐4‐oxo‐2 H ‐chromeno[4,3‐ c ]‐pyrazoles) 7 under microwave irradiation. High yields are achieved even on a gram scale, while reaction times are considerably shortened compared to conventional heating conditions.