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
W. Schroth et al., 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, Tetrahedron, 51(48), 1995, pp. 13247-13260
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.