Preparation of 1-phenylcyclohexa-2,5-diene-1-carboxylates and their use in free-radical mediated synthesesElectronic supplementary information (ESI) available: experimental procedures for the preparation of 1,4-dihydrobiphenyl,9 1-deuterio-1,4-dihydrobiphenyl, 1-phenylcyclohexa-2,5-diene-1-carboxylic acid with 3,4-dihydrobiphenyl-3-carboxylic acid, 2-(cyclohex-2-enyloxy)ethyl 1-phenylcyclohexa-2,5-diene-1-carboxylate and non-1-en-6-ol. Experimental details of the reactions of cyclopentyl 1-phenylcyclohexa-2,5-diene-1-carboxylate with cyclohexenone, methyl acrylate, methyl methacrylate, acrylonitrile and cyclohexene are included. See http://www.rsc.org/suppdata/p1/b1/b110527m/

Abstract

Synthetic routes to pure 1-phenylcyclohexa-2,5-diene-1-carboxylic acid and derived esters were developed. Esters containing appropriately unsaturated side chains generated the corresponding alkenyl radicals and hence gave good yields of 5-exo ring closure products in organotin-free reactions. Extrusion of phenyl radicals from the intermediate cyclohexadienyl type radicals was not observed, and this alternative β-scission did not compete under any conditions. Yields from alkylations of olefins in analogous intermolecular processes were, however, poor. As a spin-off from the research, it was found that 1-phenylcyclohexa-2,5-diene-1-carboxylic acid (6) was a useful source of hydroxyformyl (formate) radicals in organic solvents.