Synthesis of 4-methyl-2,3,4-trichlorotetrahydropyran and several features of the stereochemistry of the nucleophilic substitution of the ?-chlorine atom

A convenient method has been developed for the synthesis of 4-methyl-2,3,4-trichlorotetrahydropyran by the chlorination of 4-methyl-4-chlorotetrahydropyran, 4-methyl-5,6-dihydro-2H-pyran and its dichloride. A study was carried out on the reactions of 4-methyl-2,3,4-trichlorotetrahydropyran with alcohols, with sodium thiocyanate and Grignard reagents. PMR spectroscopy was used to study the stereochemistry of 4-methyl-2,3,4-trichlorotetrahydropyran and its derivatives, 2-substituted 4-methyl-3,4-dichlorotetrahydropyrans. The dechlorination of these dichloro derivatives by metallic sodium leads to 2,4-disubstituted 5,6-dihydro-2H-pyrans with high regioselectivity.