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.
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