Direct preparation of pyrrolizidines using imines and isonitriles

An acid mediated annulation reaction for the formation of 7a-substituted unnatural pyrrolizidines is described. To reach this goal, the pyrroline 3-(3,4-dihydro-2H-pyrrol-5-yl)propan-1-ol is reacted with a large variety of isonitriles directly resulting in the target compounds. The reaction is operationally simple and tolerates air and water, and the resulting pyrrolizidines can be further transformed to the corresponding oxidized and reduced derivatives