Synthesis of dihydrofuro[2,3-b]pyridines by the reaction of 2-amino-4,5-dihydro-3-furancarbonitriles with α,β-unsaturated carbonyl compounds

The reactions of 2-amino-4,5-dihydro-3-furancarbonitriles 1a-d with α,β-unsaturated carbonyl compounds in the presence of sodium ethoxide (0.1 equivalent) gave the corresponding Michael adducts 2a-d, 3a-d and 4a-d. Compounds 2a-d and 3a-c reacted with sodium alkoxide (1 equivalent) to yield the corresponding 7a-alkoxyhexahydrofuro[2,3-b]pyridines 5a-d, 6a-d, 7a-c and 8a-c. Treatment of 5a-d, 6a-d, 7a-c and 8a-c with potassium tert-butoxide produced the corresponding dihydrofuro[2,3-b]pyridines 9a-d and 10a-c. The reaction of 4a-c with sodium ethoxide (1 equivalent) afforded the corresponding dihydro-furo[2,3-b]pyridines 11a-c.