75075-63-7Relevant articles and documents
1,3-OXAZIN-6-ONES: VERSATILE INTERMEDIATES IN HETEROCYCLIC SYNTHESIS
Steglich, Wolfgang,Jeschke, Rainer,Buschmann, Ernst
, p. 361 - 372 (2007/10/02)
Methods for the preparation of 6H-1,3-oxazin-6-ones are reviewed and details of a new, efficient synthesis of the title compounds starting from tert-butyl 3-acylaminoacrylates are presented.A comprehensive table of alkyl- and aryl-substituted 1,3-oxazin-6-ones prepared by the old and new routes has been compiled.The (4+2)-cycloaddition reactions of 1,3-oxazin-6-ones with a variety of dienophiles leads to pyridines, 4-(dialkylamino)pyridines, 4-alkoxypyridines, 4H-azepines and 4H-diazepines after extrusion of CO2 from the initial products of the cycloaddition reaction.These reactions proceed in most cases with complete regioselectivity.Oxazinones in which the 2-azadiene moiety is markedly electron deficient react with pyrroles and indoles to produce dihydrooxazinones which can be further transformed to pyrroloimidazoles and indoloimidazoles, respectively.Treatment of the title compounds with ammonia affords pyrimidin-6-ones whereas with other nucleophiles, e.g. water, alcohols and amines, ring-opened products are obtained.Irradiation of 1,3-oxazin-6-ones at low temperature produces 2-oxa-6-azabicyclohex-5-en-3-ones whereas at room temperature in the presence of sensitizers, dimerization takes place.
