✦ LIBER ✦

Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8′-methylene-bis-4-oxo-1H and 2H-chromeno[4,3-C]pyrazoles

✍ Scribed by Adki Nagaraj; Cherkupally Sanjeeva Reddy

Publisher: Journal of Heterocyclic Chemistry
Year: 2007
Tongue: English
Weight: 317 KB
Volume: 44
Category: Article
ISSN: 0022-152X
DOI: 10.1002/jhet.5570440619

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✦ Synopsis

Abstract

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The 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.

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