Synthesis and characterization of aliphatic alpha-dithiones, di(1-adamantyl)- and di-tert-butylethanedithiones.
2,3-Di(1-adamantyl)thiirene 1-oxide quickly reacted with Lawesson's reagent in CH2Cl2 at room temperature to provide di(1-adamantyl)ethanedithione (1) as thermally labile, violet crystals in 20% isolated yield. The use of CS2 as the solvent gave 1 in 46% isolated yield. The reaction in the presence of dimethyl acetylenedicarboxylate furnished dimethyl 4,5-di(1-adamantyl)-2,3-thiophenedicarboxylate in 51% yield. A tentative mechanism for the formation of 1 is proposed on the basis of the experimental observations. The structure of 1 was characterized on the basis of spectroscopic data (NMR, mass, IR, Raman, and UV/vis) and DFT calculations. 1 rearranged to 3,4-di(1-adamantyl)-1,2-dithiete quantitatively with kinetic parameters of DeltaH = 17.6 +/- 0.2 kcal mol-1, DeltaS = -23.0 +/- 0.7 cal K-1 mol-1, and DeltaG = 24.4 +/- 0.4 kcal mol-1. Peracid oxidation and Pt-complex formation of 1 are also reported.