Bismuth-triflate-catalyzed Prins-Ritter reaction - An efficient synthesis of 4-amidotetrahydropyrans

Bismuth(III) triflate is found to be an effective Lewis acid in catalyzing a three-component reaction of homoallylic alcohol, carbonyl compound, and nitrile at ambient temperature via the Prins-Ritter sequence to furnish 4-amidotetrahydropyrans in high yields, all with cis selectivity. Spirocyclic 4-amidotetrahydropyrans are obtained in case of cyclic ketones.