A new method for the stereoselective synthesis of trans-2,6-disubstituted 3,6-dihydro-2H-pyrans with a variety of substitution patterns is described, involving Lewis acid induced tandem allylation or cyanation of δ-hydroxy-α,β-unsaturatedaldehydes to produce dihydropyrans in good yields and with trans-selectivity. This method is very useful for the synthesis of trans-2,6-disubstituted dihydropyran