Novel C-alkylation reaction of condensed thiophenes with enaminones, enaminonitriles, ethoxymethylene malononitrile, aryl vinyl ketones and omega-nitrostyrenes

While the thienocoumarin 1 reacts with aryl vinyl ketones, omega-nitrostyre ne and ethoxymethylene malononitrile to yield only C-1 alkylation products, it reacts with enaminones (3a-c) to yield either N-alkylated derivatives ( 4a-c) or a mixture of 4a-c and alpha,beta-unsaturated ketones (9a-c), the f ormer rearranged into the latter on prolonged boiling under reflux in 1,4-d ioxane solution in the presence of diethylamine.