Synthesis and characterization of new chiral molecules: 1,2,5,8-dithiadiazecine-6,7(5H,8H)-dione derivatives

The synthesis of ten-membered rings is not obvious. During this project, a new synthetic pathway was developed, which involves reaction of a benzothiazolium salt with a base and subsequent oxidation to air. The resulting ten-membered ring (1,2,5,8-dithiadiazecine-6,7(5H,8H)-dione 1) is inherently chiral because of constrained rotation about its interdependent stereogenic axes, and two enantiomers were detected and resolved by HPLC. The chiral properties of these enantiomers were studied by polarimetry, ECD spectrometry and X-ray and absolute configuration was assigned by DFT calculations. It was interesting to observe how chiral properties could change by oxidizing one sulphur atom, therefore 5,8-dimethyldibenzo[1,2,5,8]-dithiadiazecine-6,7(5H,8H)-dione-1-oxide 7 and 5,8-dimethyldibenzo[1,2,5,8]-dithiadiazecine-6,7(5H,8H)-dione-1,1-dioxide 8 were synthetized and characterized in the same way of compound 1.