Studies of Strained Small-Ring Compounds - Cyclopropanaphthalenes

Abstract

The synthesis of the first cyclopropa[b]naphthalene, 1,1-dichloro-2,7-diphenylcyclopropa[b]naphthalene, has been accomplished and the chemistry found to exemplify the strained nature of the three-membered ring. Replacement reactions leading towards other geminally substituted cyclopropa[b]naphthalenes have been investigated and products resulting from intramolecular rearrangement isolated. Attempts to prepare 1,1-dichlorocyclopropa[b]naphthalene have been investigated but have not been successful. The synthesis of the parent cyclopropa[b]naphthalene has been achieved by dehydrochlorination of a dichlorobenzobicyclo[4.1.0]heptene. Examination of the product mixtures has revealed the presence of competing concentration-dependent pathways, invoving base induced removal of either the benzylic or cyclopropyl protons. The analogous synthesis of cyclopropabenzene has been re-investigated and strong evidence obtained for similar competing pathways. Potential routes to cyclopropa[a]naphthalene have been proposed and considerable progress made towards the synthesis of this species.