THE SYNTHESIS OF CYCLODECANE DERIVATIVES BY INTRAMOLECULAR ALKYLATION OF AN ALPHA-PHENYLSULFENYL KETONE

The acyclic omega-tosyloxy-alpha-phenylsulfenyl ketone 1a, derived from R-(-)-carvone, underwent intramolecular alkylation to give the cyclodecenone derivative 2a in good yield. Oxidation of the sulfide to the sulfoxide and thermal elimination of phenylsulfinic acid gave the ketone 8, presumably resulting from Diels-Alder dimerization of the exomethylene ketone 9, as the major product and the endocyclic alpha,beta-unsaturated ketone 7 as the minor product. Reduction of 7 with LAH and treatment of the allylic alcohol product 10 with the sulfur trioxide-pyridine complex followed by LAH gave the (Z),(Z)-1,6-cyclodecadiene 11 and three other minor products, possibly including the sesquiterpene, helminthogermacrene (3). In contrast to the keto sulfoxide 2b, which mainly underwent exo elimination of phenylsulfinic acid, the hydroxy sulfoxide 12b, prepared from ketone 2a, underwent largely endo elimination to give the allylic alcohol 13 containing a (Z),(Z)-1,5-cyclodecadiene system.