We developed a regiodivergent
syntheses of 4- and 5-bromo-substituted
1,2,3-triazoles in copper-catalyzed azide–alkyne cycloadditions
(CuAACs) by taking advantage of bromo(phosphoryl)ethyne 1 as a bromoethyne equivalent. A one-shot dephosphorylative
CuAAC of 1 afforded 4-bromotriazoles, which was transformed
into a histone deacetylase 8 (HDAC8)-selective inhibitor, NCC-149.
However, the direct CuAAC catalyzed by CuI/Cu(OAc)2 provided
5-bromo-4-phosphoryltriazoles. The consecutive nucleophilic substitution
of the bromo group with thiols followed by MeOK-promoted dephosphorylation
gave 5-thio-substituted triazoles.
The reactions of elemental sulfur and diaryl disulfide with the compounds bearing a semipolar S→N linkage were investigated. Elemental sulfur was found to react with N-arenesulfonylsulfilimine and sulfoximine affording the corresponding sulfide and the sulfoxide respectively. Diaryl disulfide also was found to undergo similar reactions with these compounds. In the reaction of diaryl disulfide with N-arenesulfonylsulfilimine, N,N-bis-(arylthio)arenesulfonamide was obtained as a main product besides the corresponding sulfide. The mechanisms of these reactions are discussed.
Diphenyl sulfoxide and diphenyl sulfone were found to react with diphenyl disulfide at elevated temperatures, forming in both reactions diphenyl sulfide and sulfur dioxide. On the basis of 35S and 14C tracer experiments, these reactions were found to proceed through quite different mechanistic routes, viz., S–O bond fission in the case of sulfoxide and C–S bond fission in sulfone. The reactions apparently proceed through the attack of the thiyl radical on the sulfoxide and sulfone functions. Further mechanistic details of the reactions are discussed.
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