Synthesis of adamantane derivatives. Part 53. Simple synthesis of 7-thiaprotoadamantane (7-thiatricyclo(4.3.1.0 3,8 ]decane) and related derivatives via a regiospecific and stereoselective intramolecular Friedel–Crafts reaction

When heated under reflux in carbon tetrachloride in the presence of aluminium chloride, 9-thiabicyclo[3.3.1]-non-2-ene-6-carbonyl chloride (4) gave 10eq-chloro-(5) and 10ax-chloro-7-thiaprotoadamantan-2-one (6), in a ratio which depended on the conditions. The 10eq-chloro-group of (5) was more reactive than the 10ax-chloro-group of (6) in lithium aluminium hydride reduction, alkaline hydrolysis, and azido-substitution reactions. 7-Thiaprotoadamantane (7-thiatricyclo[4.3.1.03,8]decane) and some related derivatives were prepared.