Barbituric or 2-thiobarbituric acids interact with o-dialkylaminobenzaldehydes to give 5-o- dialkylaminobenzylidene derivatives, which cyclise into 2, 4, 6-trioxoperhydropyrimidine-5- spiro-3′-(1′, 2′, 3′, 4′-tetrahydroquinolines) under mild conditions; the mechanism of the key stage of a tert-amino effect reaction is disclosed on the basis of the XRD analysis of 1, 3-dimethyl-5-(2-dimethylamino-4-nitrobenzylidene) barbituric acid.
