Cyclophanes. XII* The Synthesis of [2,2](3,3')Biphenylo(3,6)-phenanthrenophanes and Attempted Conversions into Hepta[8]circulene

Abstract

[2,2](3,3')Biphenylo(3,6)phenanthrenophane-1,15-diene (6) has been synthesized by a ring-contraction procedure from the dithiacyclophane (10). The corresponding saturated compound (5) was prepared by pyrolysis of the sulfone (12). The stereochemistry of both (5) and (6) in solution has been determined to be syn from spectral evidence and neither compound shows any evidence of conformational ring-flipping or extensive mobility. Several attempts to convert the diene (6) into hepta[8]circulene are recorded. The factors affecting the photochemical ring-closures of cyclophanedienes are discussed.