Stereoselective sulfur extrusion reaction of syn- and anti-10,20-dibromo-2,3,12,13-tetrathia[4.4]metacyclophanes to the corresponding syn- and anti-dithia[3.3]metacyclophanes^†

A new cyclophane, 10,20-dibromo-2,3,12,13-tetrathia[4.4]metacyclophane (1), has been synthesized by the oxidative coupling reaction of 2,6-bis(mercaptomethyl)-1-bromobenzene with I₂. Both syn and anti isomers of 1 can be isolated at room temperature. The thermal sulfur extrusion reaction of anti-1 with (Et₂N)₃P afforded anti-9,18-dibromo-2,11-dithia[3.3]metacyclophane, while syn-1 gave 9,19-dibromo-2,11,12-trithia[3.4]metacyclophane. syn-9,18-Dibromo-2,11-dithia[3.3]metacyclophane was produced from the photochemical sulfur extrusion of syn-1 with (MeO)₃P.