The conformations of n-substituted 2,2-diaryl-1,3-dioxa-6-aza-2-silacyclooctanes in solution

Abstract 1 H, 13 C and 29 Si NMR data obtained for 2,2-diaryl-1,3-dioxa-6-aza-2-silacyclooctanes Ar 2 Si(OCH 2 CH 2 ) 2 NR indicate the occurrence in solution of an equilibrium between the conformations boat-boat/af chair-chair which are determined by the presence or absence of a transannular N → Si bond. The equilibrium is greatly affected by the electronic and steric effects of the N-and Si-substituents.