Facial selectivity in the reaction of dihalocarbenes with 2-substituted 4,7-dihydro-1,3-dioxepines

The dichloro(dibromo)cyclopropanation of conformationally heterogeneous 2-substituted 4,7-dihydro-1,3-dioxepines was found to afford a low selectivity; endo addition on the side of a remote alkyl substitutent is governed by the π-facial solvation of substrates.