Unexpected Formation and Characterization of 1-(Alkylsulfonyl)alkyl Alkanethiosulfonates via Elimination of Alkanesulfinyl Chlorides

During the preparation of propanethial S-oxide via the elimination reaction of propanesulfinyl chloride, a cepaene-like oxide product, 1-(propylsulfonyl)propyl propanethiosulfonate, was unexpectedly obtained. The structure of this product was unambiguously confirmed by HRMS, ¹H NMR, ¹³C NMR, COSY, HSQC, DEPT-135, and HMBC analyses, with further validation through reductive derivatization of the product. After optimizing the reaction conditions, 1-(propylsulfonyl)propyl propanethiosulfonate was obtained in 54% yield. Similarly, butanesulfinyl chloride and pentanesulfinyl chloride afforded the analogous products 1-(butylsulfonyl)butyl butanethiosulfonate and 1-(pentylsulfonyl)pentyl pentanethiosulfonate in 40 and 42% yields, respectively. These compounds are trivially named as tetraoxocepaenes. 1-(Propylsulfonyl)propyl propanethiosulfonate exhibits a characteristic onion-like odor and demonstrates good stability, suggesting its potential application as an onion-like flavor.