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Facile and convenient synthesis of 2,6‐disubstituted 4 H ‐1,3‐oxazin‐4‐one derivatives
Author(s) -
Morita Yasuo,
Kaneko Masakazu,
Matsuzawa Sumiko,
Yamamoto Yutaka
Publication year - 1997
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.5570340227
Subject(s) - chemistry , diketene , oxazines , acetic acid , perchloric acid , meldrum's acid , organic chemistry , catalysis , combinatorial chemistry
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).