A Highly Efficient Synthetic Protocol for Tetrahydropyranylation/Depyranylation of Alcohols and Phenols

Bismuth( III ) nitrate pentahydrate [Bi(NO 3 ) 3 · 5H 2 O] is found to be an effective catalyst for both tetrahydropyranylation and depyranylation of alcohols and phenols. Some of the major advantages of this protocol are: non‐aqueous workup, good yields, the involvement of a less‐expensive and nontoxic catalyst, and compatibility in the presence of a large number of other protecting groups. Notably, isopropylidene, benzylidene, and thioacetal groups are also unaffected under the experimental conditions. Remarkably, a selective mono‐protection of diols and primary alcohols can be achieved chemoselectively by employing the same catalyst. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)