Reaction of 2-methyl-3,4-dihydro-β-carbolin-2-ium iodide with acylmethyl halides controlled by electronic effects: a new route to 1,2-dihydroazepino[4,5-b]indoles

2-Methyl-3,4-dihydro-β-carbolin-2-ium iodide in the reaction with aryl halomethyl ketones is converted into 4- or/and 5-acyl-1,2-dihydroazepino[4,5-b]indoles depending on the electron donating effect of substituents in the aryl moiety of the halomethyl ketone.