Adducts from quinones and diazoalkanes. Part VII. The function of quinone methides in the side-chain amination of alkylquinones and in dimerisations giving ethylenediquinones

Abstract

Formed in methanol by the action of bases on the adduct (V), from diazomethane and 2-methyl-1,4-naphthaquinone, the 3-methyl-1,4-naphthaquinon-3-yl anion (XIV) is rapidly interconvertible with the quinone methide (VI) which adds primary or secondary, aliphatic or aromatic amines giving derivatives of 2-aminomethyl-3-methyl-1,4-naphthaquinone. Aliphatic amines are basic enough to react directly with the adduct (V), whereas aromatic amines require an additional base. The arylaminomethylquinones are deeply coloured because of charge-transfer phenomena, a property utilised for establishing a relation between the amount of the additional base added and the outcome of the competition between the formations of ethylenediquinone derivative (XIII) and arylaminomethylquinone. This relation and other considerations allow the competing reactions to be formulated as Michael additions of carbanions or of amines, as appropriate, to the quinone methide.