Synthesis of a naturally occurring dihydrohomopteridine insect metabolite, 6-acetyl-2-amino-7,8-dihydro-9H-pyrimido[4,5-b][1,4]diazepin-4(3H)-one

Boyle, Peter H.; Hughes, E. M.; Khattab, H. A.; Lockhart, Ronan J.

doi:10.1039/p19900002071

Cited by 7 publications

(1 citation statement)

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“…As a rule, the products possessing different substituents at C(6) and C (8) are obtained as mixtures of regioisomers, a disadvantage that is avoided by condensing 4-chloro-5-nitropyrimidines with b-amino ketones (Polonovski -Boon-type reactions) [9] [10]. Only a few examples of spirobenzodiazepines are known [4] [11] [12] and, to the best of our knowledge, no synthesis of spiropyrimido [4,5-b] [1,4]diazepines has been reported.…”

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Synthesis of Spiropyrimidodiazepines and Spirodiazepinopurines by Tandem Nitroso‐ene/Diels–Alder Reactions

Zhang

Vasella

2007

Helvetica Chimica Acta

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New spirocyclic heterocycles 8, 16, 19/20, 25, 27, and 30 derived from pyrimido [4,5-b][1,4]diazepin]-8'(9'H)-one were synthesised by a tandem nitroso-ene/Diels -Alder reaction of 4-(alkenoylamino)-5-nitrosopyrimides. The crystal structure of 16 was established by X-ray analysis. It is characterised by four pairs of intermolecular H-bonds linking every two molecules in the unit cell. Sequential imine reduction and intramolecular condensation of the C(4')-(acylamino)-pyrimido [4,5-b] Introduction. -The nitroso-ene reaction of 4-(alkenoylamino)-5-nitrosopyrimidines 1 generates allylic hydroxylamines, and is followed by in situ elimination of H 2 O, leading in high yield to C(6)-substituted pteridinones 2 [1]. We wondered about the ene reaction of the 4-(acylamino)-5-nitrosopyrimidines I (Scheme 1), possessing an Nalkenoyl group substituted at C(2) rather than at C(3). The ene reaction of I may lead either to 6,6-disubstituted pteridinones II, via the reacting conformer Ia, or to pyrimido [4,5-b][1,4]diazepines IV, via conformer Ib. Dehydration of the initial ene products should generate the quinonoid III and/or lead to pyrimido [4,5-b][1,4]diazepines V. The expected high reactivity of the intermediates and products suggested intercepting them. We planned to do so by combining the nitroso-ene reaction with a cycloaddition. The cycloaddition of V to 2,3-dimethylbuta-1,3-diene is expected to lead to spiropyrimidodiazepines VI. This imine, or the presumably more stable amine VII, should facilitate the analysis of the regioselectivity of the ene reaction, and lead to a new ring system. No issue of regioselectivity is expected for the ene raction of 4-(alkenoylamino)-5-nitrosopyrimidines I that lack the CH 2 R 4 substituent. Their tandem ene/Diels -Alder reaction was thought to lead exclusively to pyrimido [4,5-b]

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