Reactions of (+)-Camphene with Dithiols

Abstract

Electrophilic addition of thiols to camphene is known characteristically to follow various pathways and to produce both adducts that retain the starting camphene structure against Markovnikov’s rule or according to it and isomerization products that most frequently have the bornane structure [1–6]. We studied previously the BF3 Et2O-catalyzed addition of a series of thiols to (+)-camphene. Terpene sulfides with the camphene or bornane structure were formed according to Markovnikov’s rule for aromatic and heteroaromatic thiols whereas the reactions with other thiols went against the rule and retained the starting structure [7]. In continuation of research on the electrophilic addition of S-containing reagents to (+)-camphene (1), we studied its reaction with bifunctional thiols such as 1,2-ethanedithiol and bis(2-mercaptoethyl)sulfide under various conditions by varying the catalyst (BF3 Et2O or ZnCl2) and substrate:reagent ratio (Scheme 1).