Stereochemistry of reaction of 2,3-dichlorotetrahydropyrans with Grignard reagents

1. The reaction of the isomeric 2,3-dichlorotetrahydropyrans with Grignard reagents obeys thermodynamic control; the formed 2-R-3-Cl-tetrahydropyrans have the conformation of an armchair with a diequatorial arrangement of the substituents. 2. 2,3-Di-(p-chlorophenyl)-1,4-dioxane, obtained from 2,3-dichloro-1,4-dioxane and p-ClC6H4MgBr, is found in the conformation of an armchair with a cis-orientation of the phenyl rings. © 1974 Consultants Bureau