The Organocatalytic Asymmetric Prins Cyclization

We describe here the design and development of an organocatalytic Prins cyclization. In the presence of a confined chiral imidodiphosphoric acid catalyst, salicylaldehydes react with 3-methyl-3-buten-1-ol to afford highly functionalized 4-methylenetetrahydropyrans in excellent regio- and enantioselectivity. The extreme steric demand of the acid catalyst is key for the success of this transformation.