Intramolecular Diels–Alder reaction of 2-diphenylphosphinyl-5-(propargyloxymethyl)furans followed by nucleophilic 1,2-rearrangement of the phosphinyl group

The base-catalyzed intramolecular Diels–Alder reactions of 2-diphenylphosphinyl-5-(propargyloxymethyl)furans 2a–e gave the tetrahydrofuran ring annulated o-diphenylphosphinophenols 3a–e in 70–80% yields, a novel reaction involving an intramolecular Diels–Alder reaction of furan diene with allenyl ether dienophile followed by a nucleophilic 1,2-rearrangement of the diphenylphosphinyl group.