All reagents were obtained commercially unless otherwise noted. Solvents were purified by passage under 10 psi N2 through activated alumina columns. Infrared (IR) spectra were recorded on a Thermo Scientific Nicolet iS5 FT-IR spectrometer; data are reported in frequency of absorption (cm -1 ). NMR data are recorded as chemical shift in ppm referenced internally using residue solvent peaks, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet or overlap of nonequivalent resonances), integration, and coupling constant . 1 H NMR spectra were recorded at 400, 500, or 600 MHz. 13 C NMR spectra were recorded at 100 or 125 MHz. Exact mass spectra were recorded using an electrospray ion source (ESI) either in positive mode or negative mode with a time-of-flight (TOF)