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.
Kurebayashi, H., Mine, T., Harada, K., Usui, S., Okajima, T., & Fukazawa, Y. (1998). Conformational analysis of dioxa[2.2]orthocyclophanes. Tetrahedron, 54(44), 13495–13504. https://doi.org/10.1016/S0040-4020(98)00830-8