Reductive and Brominative Termination of Alkenol Cyclization in Aerobic Cobalt-Catalyzed Reactions

Tetrahydrofur-2-ylmethyl radicals were stereoselectively generated from substituted pent-4-en-1-ols in aerobic cobalt(II)-catalyzed oxidations. Intermediates were trapped with cyclohexa-1,4-diene, gamma-terpinene, BrCCl3, diethyl dibromomalonate, or electron-deficient olefins such as acrylonitrile or dimethyl fumarate to afford functionalized tetrahydrofurans in synthetically useful yields.