Cyclic sulphones. Part XVII. Probes for conjugation of the sulphonyl group: thiopyrano[3,2-b]-pyran, -pyridine, and -thiopyran SS-dioxides

Abstract

The thiopyran group in the title compounds, which have been synthesized, does not appear to reproduce the electronic situation present in thiopyran SS-dioxide anion. Thiopyrano[3,2-b]pyridine SS-dioxide shows striking spectroscopic analogies with 1-methyl-5-quinolone. I.r. stretching vibrations of the sulphonyl group in these molecules show a bathochromic shift; however the extent of this is small and indicates that little conjugation, if any, occurs through this group.