A Tandem Prins Spirocyclization for the Stereoselective Synthesis of Tetrahydrospiro[chroman-2,4′-pyran] Derivatives.

A novel cascade strategy has been developed for the synthesis of tetrahydrospiro[chroman-2,4′-pyran] derivatives by condensation of aldehydes with 2-(5-hydroxy-3-methylenepentyl)phenol. The reaction proceeds smoothly in the presence of BF3·OEt2 under mild conditions in a highly stereoselective manner leading to a single diastereomer. This approach is simple and convenient for the synthesis of pharmacologically relevant spirochroman scaffolds.