A new base-induced ring transformation of pyrido[2,3-d]pyrimidines |
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Authors: | Jun-Ichi Matsumoto Shinsaku Mishio Shinsaku Minami |
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Abstract: | 8-Substituted 5,8-dihydro-5-oxopyrido[2,3-d]pyrimidine-6-carboxylates ( 3 ) rearranged to 8-substituted 7,8-dihydro-5-hydroxy-7-oxopyrido[2,3-d]pyrimidine-6-carboxaldehydes ( 5 ) when treated with sodium ethoxide in an aprotic polar solvent at room temperature. The 6-cyano analogue ( 18 ) also underwent ring transformation under the same mild conditions giving 7-amino-8-ethyl-5,8-dihydro-5-oxopyrido[2,3-d]pyrimidine-6-carboxaldehyde ( 21 ). However, the ring transformations of the pyrido[2,3-d]pyrimidine bearing no N8-substituent ( 12 ), ethyl 1-ethyl-1,4-dihydro-4-oxo-1,8-naphthyridine- ( 14 ) and -quinoline-3-carboxylates ( 16 ) failed to occur. A mechanism is discussed. |
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