Gold-Catalyzed Enynal and Enynol Coupling by Selectively Steering Two Transient Vinyl-Gold Intermediates

Abstract

The vinyl–gold bond is easily accessible but less exploited in homogeneous gold catalysis, which possesses weak nucleophilicity and would be likely to undergo protodemetalation. Herein, a gold-catalyzed enynal and enynol coupling by selectively steering two transient vinyl-gold intermediates is realized under mild conditions. It exhibits high atom economy and good tolerance of functional groups with the added benefit of operational simplicity. The control experiments indicated that the in situ formed vinyl–gold accounts for the reactivity.

Environmentally friendly Nafion-catalyzed synthesis of 3-substituted isoquinoline by using hexamethyldisilazane as a nitrogen source under microwave irradiation

“…75 Hz),135.18 (d,J = 7.375 Hz),131.58 (2×),129.11,128.50 (2×),122.93 (d,J = 3.25 Hz),122.05,121.29 (d,J = 22.625 Hz),113.64 (d,J = 22.875 Hz),95.99,83.76. 2-( p-Tolylethynyl)benzaldehyde (2k). 30 Yield = 86% (189 mg); brown solid; mp = 42-43 °C; HRMS (FAB, M + + H) calcd for C 16 H 13 O 221.0966, found 221.0969; 1 H NMR (500 MHz, CDCl 3 ): δ 10.65 (s, 1H), 7.94 (dd, J = 1.0, 8.0 Hz,1H),1H),7.56 (td,J = 1.5,8.0 Hz,1H),7.46 (d,J = 8.0 Hz,2H),1H),7.18 (d,J = 8.0 Hz,2H), 2.38 (s, 3H); 13 C NMR (125 MHz,CDCl 3 ): δ 191.67,139.28,135.66,133.66,133.04,131.50 (2×),129.21 (2×),128.31,127.09,127.06,119.17,96.59,84.25,21.48.…”

“…2-(m-Tolylethynyl)benzaldehyde (2l). 30 Yield = 83% (183 mg); colorless gum; HRMS (FAB, M + + H) calcd for C 16 H 13 O 221.0966, found 221.0963; 1 H NMR (500 MHz, CDCl 3 ): δ 10.66 (s, 1H), 7.94 (dd, J = 1.0, 8.0 Hz, 1H), 7. 65-7.58 (m, 1H), 7.57-7.52 (m, 1H), 7.44-7.40 (m, 1H), 7.39-7.35 (m, 2H), 7.…”

“…2-((4-Methoxyphenyl)ethynyl)benzaldehyde (2o). 30 Yield = 94% (222 mg); yellow solid; mp = 41-42 °C; HRMS (FAB, M + + H) calcd for C 16 H 13 O 2 237.0916, found 237.0917; 1 H NMR (500 MHz, CDCl 3 ): δ 10. 60 (s, 1H), 7.91-7.86 (m, 1H), 7.58-7.53 (m, 1H), 7.52-7.48 (m, 1H), 7.46 (d, J = 9.0 Hz, 2H), 7.…”

“…The compound crystallizes in the monoclinic crystal system, space group P 21/c, a = 15.9038( 7 32,162.81 (d,J = 249.375 Hz),135.72,133.62 (d,J = 7.75 Hz,2×),133.52,133.06,128.55,127.27,126.45,118.37 (d,J = 3.375 Hz),115.74 (d,J = 22.125 Hz,2×),95.10,ethynyl)benzaldehyde (2s). 30 Yield = 93% (209 mg); yellow gum; HRMS (FAB, M + + H) calcd for C 15 H 10 FO 225.0716, found 225.0714; 1 H NMR (500 MHz, CDCl 3 ): δ 10.61 (s, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.64 (d, J = 7.5 Hz, 1H), 7.58 (t, J = 7.5 Hz, 1H), 7.47 (t, J = 8.0 Hz, 1H), 7. 38-7.31 (m, 2H), 7.28-7.23 (m, 1H), 7.13-7.06 (m, 1H); 13 C NMR (125 MHz, CDCl 3 ): δ 191.…”

Gold-catalyzed tandem reaction of o-alkynylphenols with diazo compounds: access to 2,3-disubstituted benzofurans

“…6 Recently, Zhu and co-workers developed a gold-catalyzed tandem reaction of o -alkynylphenols with o -alkynylbenzaldehydes to produce 2,3-disubstituted benzofurans, in which the in situ formed vinyl gold was responsible for the reactivity (Scheme 1c). 7 In continuation with our research interest in gold–carbene chemistry, 8 herein we wish to report a novel cycloaddition reaction of o -alkynylphenols with quinone diazides/diazoacetates to synthesize 2,3-disubstituted benzofurans under gold catalysis. We envisioned that the initial formation of vinyl gold species 9 between the gold catalyst and o -alkynylphenols would occur, followed by protonation and Csp 2 –H bond insertion to give the final benzofuran compounds (Scheme 1d, path a).…”