Synthesis of Pyrrolidin-5-one-2-carboxamides through Cyclization of N -Substituted-2-alleneamides.

The synthesis of pyrrolidin-5-one-2-carboxamides 6a-p has been developed via a one-pot Ugi reaction of allenic acids, primary amines, isocyanides, and aldehydes followed by regioselective cyclization of the resultant N -substituted-2-allenamides with KO t -Bu at room temperature. The cyclization reaction was carried out through a 5- exo -dig approach, which resulted in good yields and high atom-economy under transition-metal-free and mild reaction conditions.