Oxidative ring contraction of 2-phenyl-1,3-dithiane in ZSM-5: Restricted mobility of 1,2-dithiolane radical cations in zeolite channels

Incorporation of 2-phenyl-1,3-dithiane 1 into ZSM-5 generated 1,2-dithiolane radical cation 2^.+, the EPR spectrum of which shows an orthorhombic powder pattern (g₁ = 2.0293, g₂ = 2.0193, g₃ = 2.0030); each g component showed a 1:4:6:4:1 pattern (a₁ = 10.5, a₂ = 9.3 and a₃ = 9.2 G) due to coupling to four equivalent ¹H nuclei, suggesting that the pseudo-axial and -equatorial α-protons undergo conformational equilibration whereas the sulfur centers are held stationary on the EPR time scale.