Regioselective one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles from in situ generated potassium arylethynyltrifluoroborates

Abstract

1,4-Disubstituted 1,2,3-triazole derivatives, which are obtained from terminal alkynes and azides via 1,3-dipolar cycloaddition, are important small-molecule building blocks for complex compounds, and hence find significant application in organic synthesis, pharmaceutical sciences, and development of functional materials. Terminal alkynes are expensive, have low molecular weights and boiling point, have a short shelf life(storage-instable), and are difficult to handle; these problems hinder the widespread use of terminal alkynes as 1,3-dipolar cycloaddition partners of azides. Potassium arylethynyltrifluoroborates, the intermediates generated by the Sonogashira reaction of potassium ethynyltrifluroborate with various aryl halides, were directly coupled with azides in the presence of a stoichiometric amount of CuI under aqueous conditions, and the desired 1,4-disubstituted 1,2,3-triazoles were isolated in good yields. Both electron-donating and electron-withdrawing substituents on the potassium arylethynyltrifluoroborates gave moderate-to-excellent isolated yields.