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

Abstract

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 (g 1 = 2.0293, g 2 = 2.0193, g 3 = 2.0030); each g component showed a 1:4:6:4:1 pattern (a 1 = 10.5, a 2 = 9.3 and a 3 = 9.2 G) due to coupling to four equivalent 1 H nuclei, suggesting that the pseudo-axial and 2equatorial a-protons undergo conformational equilibration whereas the sulfur centers are held stationary on the EPR time scale.

1,3-Dithianes as Assembling Ligands for the Construction of Copper(I) Coordination Polymers. Investigation of the Impact of the RC(H)S2C3H6 Substituent and Reaction Conditions on the Architecture of the 0D–3D Networks

“…Mechanistic details rationalizing this unexpected extrusion of a Ph-CH unit (most probably in form of benzaldehyde) and structure of this 3D network will be reported elsewhere. 71,72 Furthermore, the PXRD of the crude product obtained by reaction of CuCl 2 and L5 matches perfectly with the one calculated from the single crystal of the CP containing 1,2 dithiolane ligand, confirming the formation of this compound as main product (Fig. S30).…”

“…Mechanistic details rationalizing this unexpected extrusion of a Ph−CH unit (most probably in the form of benzaldehyde) and the structure of this 3D network will be reported elsewhere. 71,72 Treatment of 2-Ferrocenyl-1,3-dithiane (L6) with CuI. The construction of polynuclear assemblies and coordination polymers featuring an organometallo-ligand, especially the electrochemically active and thermally robust ferrocenyl group in the main chain or as a pendant side-fragment, has stimulated much interest in material sciences.…”

Spontaneous oxidation of a sulfide in zeolite CaY: the unprecedented reaction of a sulfide radical cation with oxygen

“…Reported examples of spontaneous formation of sulfur-centered radical cations in the interior of zeolites are rare. Nevertheless, Roth and co-workers 4,5 have reported formation of both diphenyl disulfide and 2-phenyl-1,3-dithiane radical cations in ZSM-5. Electron transfer oxidations of encapsulate substrates [Scheme 1(a)] have often been discussed in terms of electron transfer to a Lewis acid or defect site formed during zeolite pretreatment or as an oxidation by absorbed oxygen.…”

“…The spontaneous formation of radical cations in zeolites has been extensively investigated with the realization that electron transfer is pivotal to many processes promoted by these important catalysts. 1 The lifetimes of radical cations are often dramatically extended in the interior of the zeolite allowing spectroscopic characterization, however, these species are not inert 2 and dimerizations, 3 rearrangements, 4 ring contractions, 5 and loss of protons 6,7 have all been observed. We report here the first example of the formation of a 2s-1s* radical cation 8 in the interior of CaY and the ability of the zeolite to promote a reaction of this radical cation that is not observed in homogeneous solution.…”

Oxidation of Arylcyclopropanes in Solution and in a Zeolite: Structure and Rearrangement of the Phenylcyclopropane Radical Cation

“…16 In others, more complex conversions occur, such as formation of p-propenylanisole radical cation from p-propylanisole (net loss of 3 e -plus 2 H + ), 17 or the conversion of 2-phenyl-1,3-dithiane to 1,2-dithiolane radical cation, which requires ring contraction with extrusion of a benzyl function. 18 The available precedent left little doubt that 1 could be oxidized in the ZSM-5 channels, but the ultimate fate of 1 •+ could not be predicted. Sequestering 1 (R ) H, OCH 3 ) into ZSM-5 19 resulted in strong EPR quintets (g ) 2.0032 ( 0.0002; A ) 11.2 G, 4H; e.g., Figure 3, R ) OCH 3 ).…”