Photochemical reactions of dithio-2,2′-dipyridine were studied by the laser flash photolysis method to clarify the structure and reactivities of the intermediate radical. The transient absorption band appearing at 490 nm was attributed to a radical in which the unpaired electron was mainly localized at the sulfur atom, namely, pyridyl-2-thio radical (2-PyS·). The low reactivities of 2-PyS· to O2 and hydrogen-atom donors were confirmed by the invariance of the decay rates of 2-PyS·. The high reactivity of 2-PyS· in addition reactions to conjugated dienes was confirmed by the accelerated first-order decay rate of 2-PyS· upon addition of the diene. For example, the addition reaction rate constant for isoprene was 1.2 × 109 M-1 s-1 (in THF), which is higher than that of PhS. Such reactivities were interpreted by comparison with MO calculations.
ASJC Scopus subject areas
- Organic Chemistry