1,7-dioxa[7](2,7)pyrenophane: The pyrene moiety is more bent than that of C-70

The synthesis of the highly strained title compound 8a was achieved by the valence isomerization and in situ dehydrogenation of the cyclophanediene 7a at only 80 degrees C. A single-crystal X-ray structure determination of 8a revealed that the pyrene moiety is remarkably bent, the two ends forming a n angle of 109.2 degrees. This degree of lengthwise bend slightly exceeds t hat present in the pyrene unit found in the equator of D-5h C-70, rendering it the most bent pyrene group yet prepared. The expectation of unusual rea ctivity is borne out by the apparent Diels-Alder reaction between 8a and te tracyanoethylene (TCNE) to give adduct 9.