Issue 3, 1999

The aza-ene reaction of heterocyclic ketene aminals with activated carbonyl compounds: a novel and efficient synthesis of γ-lactam-fused diazaheterocycles

Abstract

Reactions of heterocyclic ketene aminals with activated carbonyl compounds are strongly influenced by the structure of the heterocycle moiety. Six-membered heterocyclic ketene aminals with or without an N-methyl group such as 3 and 4 underwent efficient addition and consecutive cyclocondensation reactions with diethyl oxomalonate 9 to produce γ-lactam-fused pyrimidine derivatives 10 and 11 in moderate to excellent yield. For the five-membered enediamines, however, those compounds without any N-substituent such as 6 underwent the same reaction slowly and no reaction at all was observed with N-methyl and N,N ′-dimethyl-substituted analogs 7 and 8. Heterocyclic ketene aminals 3 also reacted with glyoxylic acid esters 17 to afford 8-aroyl-7-hydroxy-6-oxo-1,2,3,4,6,7-hexahydropyrrolo[1,2-a]pyrimidines 18 in good yield. No asymmetric induction was found, however, when (1R,2S,5R)-(–)-menthyl glyoxylate 17b was employed as a chiral substrate. An aza-ene reaction mechanism involving heterocyclic ketene aminals as the aza-ene component (H–N–C[double bond, length half m-dash]C) has been proposed. The effects of intramolecular hydrogen bonding and heterocyclic ring size on the reactivity are also discussed.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1999, 321-326

The aza-ene reaction of heterocyclic ketene aminals with activated carbonyl compounds: a novel and efficient synthesis of γ-lactam-fused diazaheterocycles

J. Zhang, M. Wang and Z. Huang, J. Chem. Soc., Perkin Trans. 1, 1999, 321 DOI: 10.1039/A808328B

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