Acid-catalysed dimerization of exo-2-Phenyl-exo-5,exo-6-trimethylenenorbornan-endo-2-ol

Abstract

The dimeric products formed by reaction of exo-2-phenyl-exo-5,exo-6-trimethylenenorbornan-endo-2- ol (1) with formic acid at 70º are identified as: (1RS,2RS,6RS,7RS,8RS,1'SR,2'SR,10'SR,11'RS,- 12'RS,16'SR) - 2'- phenylspiro[tricyclo[5,2,1,0^2,6]decane- 8,9'-pentacyclo[9,5,1,0^2,10,0^3,8,0^12,16]hepta-deca-3',5',7'-triene] (5) and from X-ray diffraction data: (1RS,2RS,6RS,7RS,8RS,l'RS,2'RS,10'RS,-1l'SR,12'SR,16'RS)-2'-phenylspiro[tricyclo[5,2,1,0^2,6]decane-8,9'-pentacyclo[9,5,1,0^2,10,0^3,8,0^12,16]- heptadeca-3',5',7'-triene] (8) refined to a residual of R 0.069 (1529 observed reflections). The mechanistic implications of the formation of dimers (5) and (8) and the influence of the exo-trimethylene bridge on the dimerization process are discussed.