1 -Methyl-1,2-dihydroquinoline, formation

Reduction of quinolines in acid solution at a lead cathode or by dissolving zinc leads to attack on the heterocyclic ring with the formation of 4,4-coupled products, together with the tetrahydroquinoline [82,83]. In the case of 2- and 4-methyl substituted quinolines, dimeric products are obtained in 10 90 % yields. In these processes, dimerization of the one-electron addition product is in competition with further reduction to give the 1,4-dihydroquinoline, The latter is an enamine and it... 

Type of reaction C-C bond formation Reaction condition solid-state Keywords A-methyl cyclohex-1-enylanilide, cycloaddition, 3,4-dihydroquinolin-2(l//)-one... 

This reaction is assumed to involve the formation of ketylidene or alkylidene anils, which dimerizes and cyclizes to give 1,2-dihydroquinoline. This intermediate then aromatizes by evolving the methyl or other hydrocarbon moiety in the presence of an acidic or a basic catalyst. An illustrative mechanism is given here for the reaction between acetone and aniline hydrochloride. 

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