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Reaction of 4,5‐diaminopyrimidine and ethyl acetoacetate: Synthesis and chemistry of isomeric dihydropyrimido[4,5‐ b ][1,4] diazepinones
Author(s) -
Israel Mervyn,
Tinter S. Karin,
Trites Dorothy H.,
Modest Edward J.
Publication year - 1970
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.5570070505
Subject(s) - chemistry , ethyl acetoacetate , moiety , yield (engineering) , medicinal chemistry , alkoxide , catalysis , bicyclic molecule , ring (chemistry) , stereochemistry , organic chemistry , materials science , metallurgy
Abstract Depending upon reaction conditions, 4,5‐diaminopyrimidine and acetoacetic ester gave a variety of condensation products, including the two isomeric dihydropyrimido[4,5‐ b ][1,4]‐diazepinones. Under conditions leading to bicyclic products, the formation of 1,5‐dihydro‐4‐methyl‐2 H ‐pyrimido[4,5‐ b ][1,4]diazepin‐2‐one ( 2 ) was strongly favored. The isomeric 3,5‐dihydro‐2‐methyl‐4 H ‐4‐one compound ( 4 ) was best obtained by cyclization of ethyl 3‐(4‐amino‐5‐pyrimidylamino)crotonate ( 3 ) under base catalysis. Thermal rearrangement of 2 and 4 proceeded, in each instance, with loss of the isopropenyl moiety and gave 8‐purinone. Compound 4 underwent ring contraction under the influence of alkoxide to yield a product which was shown to be the 7‐isopropenyl‐8‐purinone ( 6 ).