An expeditious synthesis of 1,2,3,4-tetrahydro-1,1-dimethylphenanthrenes

Abstract

A simple convergent and general method has been developed for the synthesis of 1,2,3,4-tetrahydro1,1-dimethylphenanthrenes 4a–f and a few 1,2,3,4,9,10-hexahydro-1,1 -dimethylphenanthrenes 5c–f by polyphosphoric acid catalysed reaction of the easily accessible 2-(2-arylethyl)-3,3-dimethylcyclohexanones 3a–f. The tetrahydrophenanthrenes 4a,c,e,f have been converted to the respective benzylic ketones 6a,c,e,f by oxidation with pyridinium chlorochromate and Celite.