Chemistry of <i>N</i>-Thiosulfinylanilines. II. Thermolysis and Photolysis of <i>N</i>-Thiosulfinylanilines

Abstract

Abstract Thermolysis of 2,4-di-t-butyl-6-methyl-N-thiosulfinylaniline (1) in refluxing benzene afforded 2,4-di-t-butyl-8-thia-9-azabicyclo[4.3.0]nona-2,4,6,9-tetraene (6) and 2,4-di-t-butyl-6-methylaniline (7), while its photolysis resulted in the formation of N,N′-bis(2,4-di-t-butyl-6-methylphenyl)sulfur diimide (17) and 7. The mechanism of the thermolysis involving 1,5-hydrogen migration and o-quinonoid intermediate has been proposed. The electronic spectrum of the initial intermediate in the photolysis was obtained in EPA matrix and tentatively assigned to a dithionitro compound (42) or a dithiaziridine (41). Thermolysis of 2,4,6-tri-t-butyl-7,8-dithia-9-azabicyclo[4.3.0]nona-2,4,9-triene (4b) equilibrated with 2,4,6-tri-t-butyl-N-thiosulfinylaniline (4a) gave 4,6-di-t-butyl-3H-1,2,3-benzodithiazole 2-oxide (26) and 2,4,6-tri-t-butylaniline (27). The reaction in the presence of a catalytic amount of p-toluenesulfonic acid improved the yield of both 26 and 27, suggesting the ionic decomposition pathway. However, an ESR signal was observed during the thermal decomposition of 4 in the absence of oxygen, implying a concurrent homolytic pathway if not a major one. The mechanism of these reactions are briefly discussed. The photolysis of 4 led to 27 and N,N′-bis(2,4-di-t-butyl-6-methylphenyl)sulfur diimide (43).