InCl3-catalyzed stereoselective synthesis of C-glycosyl heteroaromatics

Glycals react smoothly with furan in the presence of a catalytic amount of indium trichloride at ambient temperature to afford predominantly the C-3-substituted glycals in high yields. Other heteroaromatics including 2-benzyloxymethylfuran, thiophene and N-Boc protected indole afford exclusively C-1-glycosides in good yields with high β-selectivity under similar reaction conditions.