Facile and convenient synthesis of 2,6-disubstituted 4H-1,3-oxazin-4-one derivatives

✍ Scribed by Yasuo Morita; Masakazu Kaneko; Sumiko Matsuzawa; Yutaka Yamamoto

• Publisher: Journal of Heterocyclic Chemistry
• Year: 1997
• Tongue: English
• Weight: 361 KB
• Volume: 34
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570340227

✦ Synopsis

Abstract

Facile and convenient methods for the preparation of a variety of 2,6‐disubstituted 4__H__‐1,3‐oxazin‐4‐ones 3 by three complementary methods are described. Treatment of the branched aliphatic imidate 2c,d with diketene 1 in the presence of a catalytic amount of acetic acid affords 2‐substituted 6‐methyl‐1,3‐oxazin‐4‐ones 3c,d, whereas the unbranched imidate 2b,e gave oxazines 3b,e and pyrimidines 4b,e (Method A). The reaction of acyl Meldrum's acid 5 with imidate 2 afford 2,6‐disubstituted oxazine 3, though the alkylimidate with acetyl Meldrum's acid yielded 3 and 5‐acetyl‐1,3‐oxazine‐4,6‐dione 8 (Method B). The cylodehydration of acylacetylcarboxamide 13 with acid, such as 70% perchloric acid or fluorosulfonic acid, afforded 1,3‐oxazines 3 (Method C).