Regioselective Formylation of 1-(2-Oxiranylmethyl)-4,5,6,7-tetrahydroindole with DMF/(COCl)2: the Pyrrole vs. Oxirane Nucleophilicity

Treatment of 1-(2-oxiranylmethyl)-4,5,6,7-tetrahydroindole with the DMF/(COCl)2 reagent system in CH2Cl2 (room temperature, 40 min) starts oxirane opening to give 1-(3-chloro-2-hydroxypropyl)-4,5,6,7-tetrahydroindole followed by the formylation of the pyrrole ring to end up with the formation of 1-(3-chloro-2-formyloxypropyl)-4,5,6,7-tetrahydroindole-2-carboxaldehyde via the intermediate 1-(3-chloro-2-hydroxypropyl)-4,5,6,7-tetrahydroindole-2-carboxaldehyde.