Regioselective aryl radical cyclisation. Part 2.1 Synthesis of octahydro-1H-dibenzo[a,d]cycloheptenes through 7-endo ring closure

Abstract

A simple convergent synthesis of trans- and cis-octahydro-1H-dibenzo[a,d] cycloheptenes 15a–c and 16a–c and 20a–c and 21a–c through implementation of a regioselective 7-endo-trig-aryl radical cyclisation of the respective 2-(o-bromoarylethyl)-1-methylenecyclohexanes 6a–c and 8a–c with tributyltin hydride is described. The scope of the 7-endo aryl radical cyclisation has been further demonstrated by the synthesis of (2SR,4aRS,11aSR)-methyl 1,1-dimethyl-2,3,4,4a,5,10,11,11a-octahydro-1H-dibenzo[a ,d]cycloheptene-2-carboxylate 29.