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Communication | Special issue | Vol 7, No. 1, 1977, pp.81-104
Published online, 1st January, 1970
DOI: 10.3987/S-1977-01-0081
Cyclophanes XI. The Synthesis and Comformational Behavior of 3,6-Diketo[8](2,5)thiophenophane. (3,6-Diketo[8](2,5)thiophenophane)

Alice W. Lee, Philip M. Keehn,* Socorro M. Ramos, and Stuart M. Rosenfeld

*Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02454-9110, U.S.A.

Abstract

3,6-Diketo[8](2,5)thiophenophane (1c) was synthesized by hydrolysis of [2.2](2,5)furano(2,5)thiophenophane (3). The conformational behavior of the thiophene ring and the diketo-chain in 1c was then studied by variable temperature nuclear magnetic resonance techniques. With similar studies on the deuterated derivative 5, the energy barrier associated with ring and chain flipping was found to be 16.0 and 11.4 kcal/mol, respectively. This is the first case in which a thiophenoid nucleus within a cyclophane macrocycle is found to be mobile and the first instance in which the conformational motions and associated energetics of both the aromatic ring and aliphatic chain in a cyclophane have been established.