Conformational analysis of dioxa[2.2]orthocyclophanes

Abstract

Conformations of dioxa[2.2]orthocyclophanes (5,8-dihydro-1,4- dibenzo[b,f]dioxocine) were examined by theoretical calculations and X-my crystallographic analysis. In the crystalline state a twist boat form was observed, which is identical to the structure predicted both by molecular mechanics and molecular orbital calculations. By contrast, an unique screw conformation was observed in a cyclophane having two dioxa[2.2]orthocyclophane units within the molecule in the crystalline state.