One pot hydroformylation/Intramolecular aldol condensation reactions of 1-allyl-2-carbonylpyrroles: a new entry into hydroindolizines synthesis

7-formyl-5-methyl-5,6-dihydroindolizine and 7-formyl-6-methyl-5,6-dihydroindolizine were obtained via a domino hydroformylation/cyclization/dehydration reactions sequence starting from the corresponding 1-allyl-2-formylpyrroles. An intramolecular aldol condensation between the carbon atom adjiacent to the formyl group in the chain of the produced aldehydes and the carbonyl group directly bonded to the pyrrole ring most likely generates the indolizine structure. 7-formyl-6,8-dimethyl-5,6-dihydroindolizine was similarly synthesized by using 2-acetyl-1-(2-methylprop-2-enyl)pyrrole.