The synthesis, characterization, and catalytic activity of [CuII(M1-T2)Cl][Cl] in ATRA reactions of monohalogenated compounds to alkenes in the presence of ascorbic acid and weak base are reported. Cyclic voltammetry experiments showed a reduction potential of -835 mV relative to the Fc/Fc+ couple for the Cu(M1-T2)Cl complex, implying it should be a more active catalyst for ATRA reactions than its analogue Cu(TPMA)Cl (Figure 1). Single-crystal X-ray diffraction studies indicated a distorted trigonal bipyramidal geometry for [CuII(M1-T2)Cl][Cl] with a τ value of 0.75. UV-Vis spectroscopy confirmed that the [CuII(M1-T2)Cl][Cl] complex retained this structure in solution; however, trigonal bipyramidal geometry was lost upon the addition of HCl, which is produced in ATRA reactions that utilize ascorbic acid. When a weak base was added, UV-Vis studies affirmed the geometry of [CuII(M1-T2)Cl][Cl] was retained upon addition of HCl, indicating that the presence of a weak base inhibits catalyst degradation. ATRA reactions of chloroacetonitrile to methyl acrylate were performed using [CuII(M1-T2)Cl][Cl] and [CuII(TPMA)Cl][Cl] at a catalyst loading of 250:1 relative to alkene. In the presence of 2,2-6,6-tetramethylpiperidine, 1H-NMR spectroscopy showed a monoadduct yield of 68% for [CuII(M1-T2)Cl][Cl] surpassing that of [CuII(TPMA)Cl][Cl], which produced a 35% yield. When base was absent from these reactions, less than 10% methyl acrylate conversion was observed.

Novel and highly efficient copper catalysts for atom transfer radical addition (ATRA) of monohalogenated compounds

254th National Meeting (2017)

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