CAMPHENE AND β-PINENE IN SULFENYLCHLORINATION REACTIONS
In continuation of studies on the non-catalytic reactions of sulfenyl chlorination of monoterpenes, we studied the synthetic possibilities of (+)-camphene in the reactions with methylsulphenyl- and 1-phenyltetrazole-5-sulfenyl chlorides. The reactions were carried out in methylene chloride at -20°C; the ratio of camphene:sulfenyl chloride ranged from 1:1 to 1:4. The reaction product of methylsulphenyl chlorination of camphene is a mixture of two E, Z-isomers in a ratio of 4:1. The reaction of camphene with 1-phenyltetrazole-5-sulfenyl chloride leads to the formation of three products: two unsaturated compounds (E, Z-isomers with respect to each other) and one adduct (which structure could not be established), in ratio of 5:1:3, respectively. On the base of spectral and published data we found that the E-isomer is predominant while Z-isomer is minor one. The predominant formation of the E-isomer is probably due to its greater thermodynamic stability. Reactions of β-pinene with methyl- and phenylsulfenyl chlorides were carried out under the same conditions. The use of equimolar amounts of reagents resulted in low yields of target products formation and significant amounts of unreacted terpene in the reaction mixtures. It was found that the ratio of terpen:sulfenyl chloride, characterizing the complete course of the reaction, is 1:2. As a result of sulfenyl chlorination of β-pinene, the menthene structure products were obtained. Thus, sulfenyl chlorination reactions of bicyclic monoterpenes, camphene and β-pinene, lead not to “normal” addition products, but lead to unsaturated mono- and bisulfides containing chlorine atom.