Thiopyranyl radicals

Ultraviolet spectrophotommetry was used to follow the course of the photoreduction of thiopyrylium salts to their corresponding 4H-thiopyranyl radicals (85BCJ2600) as well as the kinetics of thiopyrylium salt transformations to thiopyrans with various nucleophiles (84JA7082, 84JOC1806 86JA3409). 

The ESR spectrum of the 2,4-diphenylcyclopenta[A]thiopyranyl radical 248 is a 1 2 1 triplet attributed to interaction between the unpaired electron and the magnetic nuclei of the protons at the 7-position. Further splitting is associated with interaction with the phenyl rings (Equation 11) <2003MI1287>. 

C. Radicals Containing a Six-Membered Heterocycle 1. Thiopyranyl Radicals and Related Species... 

Consistent with prediction,reduction of thiopyrylium ions with zinc metal in acetonitrile produces transient thiopyranyl radicals which dimerize by coupling at the 4-position. The first thiopyranyl radical to have been characterized by ESR is 2,4,6-triphenylthiopyranyl (159) for which a geometry has been deduced which is closely similar to its oxygen analog (29) ... 

---