Conformational aspects of some odd-membered disulphide-bridged metacyclophanes derived from m-dimethoxybenzene

Abstract

The stereochemistry in solution of three 13- to 17-membered metacyclophanes derived from m-dimethoxybenzene (1)–(3), containing sulphide and/or disulphide linkages, has been investigated by means of ¹H n.m.r. spectroscopy. A correlation of the ¹H n.m.r. data of these molecules with those of suitable open-chain and cyclic models (4)–(10) has led to the conclusion that the 13-membered 1,2,9,16-tetrathia[2.1.1]metacyclophane (1) and the 15-membered 1,2,9,10,17,18-hexathia[2.2.2]-metacyclophane (3) adopt a propeller-like conformation, while the 17-membered 1,2,9,16,23-pentathia[2.1.1.1]metacyclophane (2) exists preferentially in the saddle-shaped conformation.