Medium-sized cyclophanes. Part 55. Synthesis and conformational studies of [2.1.1]orthocyclophanes

Abstract

[2.1.1]Orthocyclophanes 2 are prepared by pyrolysis of the corresponding 2-thia[3.1.1]orthocyclophane 2,2-dioxides 9, which are prepared by the reaction of 1,2-bis(2-bromomethylbenzyl)benzenes 7 with Na₂S in ethanol under high dilution conditions, followed by oxidation with m-chloroperbenzoic acid. The conformational studies on [2.1.1]orthocyclophanes 2, which adopt flexible saddle and crown structures in comparison with the corresponding 10,15-dihydro-5H-tribenzo[a,d,g]cyclononene ([1.1.1]orthocyclophane) 1, are discussed.