The making of molecular belts and collars

Abstract

This article relates the first encouraging steps towards the fulfilment of a long-standing research goal aimed at turning the chemistry of laterally-fused six-membered rings through 90° ... or, more specifically, the making of (i) beltenes, in which 1,4-cyclohexadiene rings are linked in a polycyclic array by lateral fusion through their carbon-carbon double bonds, (ii) collarenes, in which alternating benzene and 1,4-cyclohexadiene rings are fused to form macropolycyclic hydrocarbons and (iii) cyclacenes, which may be considered as two annulenes joined to each other by carbon-carbon single bonds between every other atom around the annulene rings. The synthesis of the key macropolycyclic compound, which is a potential precursor of [12]beltene and [12]collarene, exploits the amazing stereoelectronic control that exists in the Diels-Alder reaction between a bisdiene and a bisdienophile with the appropriate structural features and reactivity characteristics. © 1989 Kluwer Academic Publishers.