Enaminones as building blocks in heterocyclic synthesis: New syntheses of nicotinic acid and thienopyridine derivatives

✍ Scribed by Mervat Mohammed Abdelkhalik; Afaf Mohammed Eltoukhy; Samia Michel Agamy; Mohammed Hilmy Elnagdi

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2004
• Tongue: English
• Weight: 140 KB
• Volume: 41
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570410321

✦ Synopsis

Abstract

Reacting 1,3‐diphenyl‐propan‐2‐one with equimolecular amount of dimethylformamide dimethylacetal afforded the enaminone 4. This when reacted with another equimolecular amount of dimethylformamide dimethylacetal afforded the dienaminone 5. Compound 4 condenses with cyanothioacetamide and with cyanoacetamide to yield 2‐thioxo‐ and 2‐oxo‐pyridine‐3‐carbonitrile derivatives 6a,b respectively. Compound 6a reacted with α‐chloroacetone 8 to yield the thieno[2,3‐b]pyridine derivative 10 that cyclized further into 4,7,8‐trisubstituted pyrido[2′,3′:2,3] thieno[4,5‐d]pyrimidine 12. Compound 4 also afforded 2,5,6‐trisubstituted nicotinic acid ethyl ester 13 by reaction with ethyl acetoacetate in acetic acid in the presence of ammonium acetate. The dienaminone 5 reacted with acetic acid, ammonium acetate/acetic acid, phenylhydrazine and 5‐amino‐3‐methylpyrazole yielding 3,5‐diphenyl‐pyran‐4‐one 15a, 3,5‐diphenyl‐1__H__‐pyridin‐4‐one 15b and 1,3,5‐trisubstituted pyridin‐4‐ones 16a‐b.