The cycloaddition reaction of 2-benzylidenetetralin-1-thione S-oxide with acrylonitrile (or styrene) gave a mixture of 2- and 3-cyano(or phenyl)-4-phenyl-3,4,5,6-tetrahydro-2H-naphtho[1,2-b]thiopyran S-oxide. Pummerer reaction of these S-oxides resulted to afford the corresponding acetates.