General Experimental. 1 H NMR and 13 C NMR spectra were recorded at Bruker Avance 400 MHz NMR spectrometer with solvent residual peak (CDCl 3 : 1 H = 7.24 ppm, 13 C =77.23; (CD 3 ) 2 CO: 1 H = 2.05 ppm, 13 C = 206,68 ppm; (CD 3 ) 2 SO: 1 H = 2.50 ppm, 13 C = 39.51 ppm) as the internal reference unless otherwise noted. Data are reported in the following order: chemical shifts are given (δ); multiplicities are indicated b (broadened), s (singlet), d (doublet), t (triplet), q (quartet), m

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... t), app (apparent); coupling constants, J, are reported in Hz. Peaks in IR are reported in cm -1 with the following relative intensities: s (strong, 67-100%), m (medium, 40-67%), w (weak, 10-40%). HPLC analyses were carried out on an Acquity UPLC-MS Instrument (Waters Corporation), GC-MS analyses on Agilent GC-MS System (Agilent Technologies). Elemental analyses were carried out on Perkin Elmer PE 2400 Series II. High-resolution mass spectra were obtained on a LTQ Orbitrap XL (EI). IR spectra were measured with Bruker IFS 55 Equinox. Melting points were determined on a Boetius block and are not corrected. Column chromatography procedures were followed using 70-230 µm silica gel. Visualization was effected with ultraviolet light. Terminal acetylenes, were obtained from commercial sources and used without further purification. Solvents such as DMF, DME for reaction media were obtained from commercial sources, dried over 4 Ǻ molecular sieves and titrated for water level with a Karl Fischer Coulometer (Mettler Toledo DL 32) (water content below 10 ppm). Synthesis of N-thioamides and Terminal Acetylenes N-Thioamide 2b-2e, N-Thioimide 2g, tert-butylthio derivative 6f, 2-chloro-5-nitrobenzoyl chloride and copper(I) 3-methylsalicylate (CuMeSal) were prepared according to the previously reported procedure. 1,2 1 Henke, A.; Srogl, J. S4 2-Chloro-N-(2,4-dimethoxyphenyl)-5-nitrobenzamide (8b). Amide 8b was obtained from 2,4-dimethoxyaniline (5.0 g; 32.64 mmol) and 2-chloro-5nitrobenzoyl chloride (6.0 g; 27.27 mmol) as a yellow-orange crystalline product after recrystallization from acetone in 89% yield (8.20 g). M.p.186-186.5 °C. 1 H NMR (400 MHz, DMSO-d6): δ 9.86 (s, 1H), 8.35 (d, J = 2.7, 1H), 8.31 (dd, J = 2.8, 8.8, 1H), 7.84 (d, J = 8.8, 1H), 7.73 (d, J = 8.7, 1H), 6.66 (d, J = 2.6, 1H), 6.56 (dd, J = 2.7, 8.8, 1H), 3.81 (s, 3H), 3.78 (s, 3H). 13 C NMR (101 MHz, DMSO-d6): δ 163.0, 157.2-(tert-Butylthio)-N-(2,4-dimethoxyphenyl)-5-nitrobenzamide (7b). tert-Butylthioether 7b was obtained from amide 8b (7.4 g; 21.98 mmol) as a yellow crystalline product after recrystallization from acetone in 92% yield (7.9 g). M.p.161-163 °C. 1 H NMR (400 MHz, DMSO-d6): δ 9.81 (s, 1H), 8.33 (d, J = 2.6, 1H), 8.27 (dd, J = 2.7, 8.6, 1H), 7.89 (d, J = 8.6, 1H), 7.78 (d, J = 8.7, 1H), 6.66 (d, J = 2.6, 1H), 6.56 (dd, J = 2.6, 8.8, 1H), 3.84 (s, J = 20.0, 3H), 3.77 (s, J = 5.1, 3H), 1.34 (s, 9H). 13 C NMR (101 MHz, DMSO-d6): δ : 3215 m (NH), 3194 m (NH), 1657 s (CONH), 1536 s (CONH), 1524 s (NO 2 ), 1348 s (NO 2 ), 1286 s, 1209 s, 1158 s, 1045 m, 1034 m, 930 m, 832 m, 741 m cm -1 . Anal. calcd for C 19 H 22 N 2 O 5