The Chemistry of dialkoxy disulfides and related compounds /

New acyclic dibenzyloxy disulfides substituted in the para position were prepared by a modified procedure in very high yield ( ca. 85%). Each of them were found to display an AB quartet in the 1H NMR spectrum, suggesting the possible existence of the isomeric thionosulfite structure (RO)2S=S in contrast to the more commonly proposed linear structure R-O-S-S-O-R. This structure question was addressed by preparing a series of closely related compounds including the analogous disulfide R2S2, tetrasulfide R2S4, "oxytrisulfide" R-O-S3-R, sulfoxylate R-O-S-O-R, sulfite (RO)2S=O, cyclic thionosulfite and corresponding cyclic sulfite, followed by comparative 1H and 13C NMR studies. The solid state structure was established to be linear according to X-ray analysis with somewhat short S-S bond length compared with conventional disulfide structures. The possible interconversion between the linear and the branched isomer was ruled out following an extensive spectroscopic study including 17O NMR, IR, Raman and UV.The solid/solution structure was established to be linear with a rigid gauche conformation dependent of a barrier to rotation of ca. 18 kcal mol-1 (Tc = 75°C). This barrier was responsible for the diastereotopicity of the adjacent benzylic protons, giving rise to asymmetric induction, and permitted the detection of the enantiomers with the chiral shift reagent Eu(hfc)3 in chloroform at room temperature. The existence of rotational diastereomers was demonstrated by 1H and 13C NMR for chiral dialkoxy disulfides prepared from enantiomerically pure chiral and racemic alcohols.A temperature dependent NMR study revealed that dibenzyloxy disulfides can deliver singlet diatomic sulfur S2. The thermolysis was studied in different solvents in the presence of different dienes. The disulfide adduct and the diene were comparably competitive for the S2 transfer. Tetrasulfide adducts were obtained in the presence of dimethyl and diphenyl butadiene, but converted to the disulfide adduct upon triphenylphosphine treatment. The related "oxytrisulfide" was demonstrated to also transfer the S2 unit to dienes. A brief analysis of a known thionosulfite has shown its potential to transfer S2 units to dienes. Mechanistic considerations were proposed to rationalize the olefinic compounds formed.Triphenylphosphine desulfurization of dialkoxy disulfides yielded the corresponding sulfoxylates. The kinetics of the conversion of these to the corresponding sulfinates RO(S=O)R were examined and found to be first order; the Arrhenius parameters were determined