3-EXO,3'-EXO-(1R,1'R)-BITHIOCAMPHOR - A VERSATILE SOURCE FOR FUNCTIONALLY DIFFERENT 3,3'-BIBORNANE DERIVATIVES .1. RING-CLOSURE REACTIONS AND PROTOTROPIC REARRANGEMENTS

The title compound 3, derived from (+)-camphor, allows preparatively u seful conversions to be carried out at the 3,3'-bibornane skeleton. Th e reactions are characterized by steric factors. Despite the increasin g steric strain in the bicyclic units, ring-closure reactions of 3 to born-2-ene anellated sulfur-heterocycles are possible, including the f ormation of the 1,2-dithiine (6), thiophene (11), and 1,2,3-trithiepin e system (13), respectively. Compound 6 is distinguished by several un usual properties. In contrast to the normal behaviour of aliphatic thi oketones, 3 cannot exist as enthiol. The latter and related intermedia tes are immediately stabilized by 1,5-prototropic rearrangements leadi ng to bomylidene units e.g. in 16 and consecutive products.