Metal-catalyzed cycloisomerization reactions of cis-4-hydroxy-5-alkynylpyrrolidinones and cis-5-hydroxy-6-alkynylpiperidinones: synthesis of furo[3,2-b]pyrroles and furo[3,2-b]pyridines.

Furo[3,2-b]pyrroles and furo[3,2-b]pyridines can be conveniently prepared in good yields from the cycloisomerization reactions of cis-4-hydroxy-5-alkynylpyrrolidinones and cis-5-hydroxy-6-alkynylpiperidinones, respectively, using Ag(I), Pd(II)/Cu(I), or Au(I) catalysis. In one case, the cycloisomerization product was unstable and produced a furan derivative by a ring-opening reaction.