Reactions between enaminones and enones. Part 1. Some unexpected products from the condensation of 3-aminocyclohexenones with methyl vinyl ketone

Methyl vinyl ketone readily undergoes acid-catalysed condensation with 3-amino-5,5-dimethylcyclohex-2-enone to give an unstable dihydropyridine which spontaneously disproportionates. The same mixture is obtained when 2-(3-oxobutyl)dimedone reacts with ammonia in toluene, but in xylene a single, tetracyclic product is obtained. In the absence of acid, the dihydropyridine can be trapped by an excess of methyl vinyl ketone to give a hexahydro pyranoquinoline. Some primary amines react with 2-(3-oxobutyl)dimedone to give dienaminones.