Peer-Reviewed Journal Details
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Heaney, F,Burke, C,Cunningham, D,McArdle, P
2001
January
Journal Of The Chemical Society-Perkin Transactions 1
Pyrimidine annelated heterocycles - synthesis and cycloaddition of the first pyrimido[1,4]diazepine N-oxides
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Optional Fields
INTRAMOLECULAR 1,3-DIPOLAR CYCLOADDITION POTENTIALLY USEFUL INTERMEDIATE AZEPINE-RING FORMATION ENE REACTIONS 1,3-AZAPROTIO CYCLOTRANSFER ACID DERIVATIVES ZH SYSTEMS PERIPHERY NITRONES OXIMES
622
632
5-Formyl- and 5-acetyl-4-(alkenylamino)pyrimidines 5 have been prepared as precursors to novel pyrimido[1,4]diazepine N-oxides 3. In addition to cyclisation to the targeted dipoles the substrates 5 have also been observed to form imidazopyrimidines 12 and 39 via an intramolecular Michael addition; additionally 5b has been observed to form the pyrimidoazepinone 42. Aldonitrone 3a cycloadded readily to olefinic dipolarophiles; ketodipole 3b did not share this reactivity. Both dipoles reacted with acetylenic dipolarophiles but the ensuing cycloadducts 37 were unstable; facile ring contraction of their isoxazolopyrimidodiazepine skeletons to the pteridine nucleus is noted. The structure of 37c has been determined by X-ray crystallography.
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