Reaction of Cy2NH with CS2 in NaOH/H2O, followed by oxidation with I2, yields a complex mixture that includes the tetracyclohexylthiuram disulfide, Cy2NC(S)SSC(S)NCy2, in mixture with S8 and the tetrasulfide Cy2NC(S)SSSSC(S)NCy2. Direct reaction of 2 eq of Cy2NH with CS2 in EtOH, followed by I2 oxidation, does not yield isolable Cy2NC(S)SSC(S)NCy2, even though other tetraalkylthiuram disulfides are effectively produced by this protocol. Deprotonation of Cy2NH with t BuLi, followed by treatment with CS2 and then oxidative coupling with I2 yields Cy2NC(S)SSC(S)NCy2 in ∼74% yield, suggesting secondary amines that are branched at the α carbon may generally require this lattermost approach to the corresponding tetraalkylthiuram disulfide. Evaporation of an Et2O solution of the crude product mixture obtained from the CS2/NaOH/H2O reaction yielded a triclinic form of Cy2NC(S)SSC(S)NCy2, which contained two independent molecules in its asymmetric unit with opposite C 2 handedness. This same product mixture contained Cy2NC(S)SSSSC(S)NCy2, which was identified crystallographically in monoclinic C2/c and is the first such tetrasulfide to be characterized by X-ray diffraction. A second polymorph of Cy2NC(S)SSC(S)NCy2, obtained by evaporation of an acetone solution, is disordered across a mirror plane in monoclinic P21/m. This monoclinic polymorph of Cy2NC(S)SSC(S)NCy2 is the only tetraalkylthiuram disulfide found to crystallize on a mirror plane.
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