Decarboxylation,during their aromatization by Pd/C,of some 3,4-octahydronaphtho-7,8-benzocoumarins : Synthesis of 1,2'-binaphthyls and 2,2'-binaphthyls

Some 3',4'-cyclohexa-1',2'-dihydro- and 1',2'-cyclohexa-3',4'-dihydro-3,4,7,8-dibenzocoumarins 2 and 3 were prepared by catalytic condensation between a naphthol and a α-carbethoxy-cis- decalone (?1 or ?2). These compounds, when treated with Pd/C at 260°, undergo, beside aromatization, a complete decarboxylation of the lactone ring. A mechanism, involving H transfer through a π-allylic palladium complex is described.