Synthesis of C,N,N-Cyclometalated Gold(III) Complexes with Anionic Amide Ligands

Ryotaro Niizeki; Kosuke Higashida; Emna Mejri; Masaya Sawamura; Yohei Shimizu

doi:10.1055/a-1673-9236

Synlett, Table of Contents

Synlett 2022; 33(03): 288-292
DOI: 10.1055/a-1673-9236

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Synthesis of C,N,N-Cyclometalated Gold(III) Complexes with Anionic Amide Ligands

Ryotaro Niizeki

^aDepartment of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

,

Kosuke Higashida

^aDepartment of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

^bInstitute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan

,

Emna Mejri

^aDepartment of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

,

Masaya Sawamura ∗

^aDepartment of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

^bInstitute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan

,

Yohei Shimizu ∗

^aDepartment of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

^bInstitute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan

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Abstract

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Dedicated to Professor Christian Bruneau for his outstanding contribution to catalysis.

Abstract

A series of neutral C,N,N Au(III) complexes were synthesized with N-(8-quinolinyl)benzamide derivatives or chiral N-[2-(1,3-oxazolin-2-yl)phenyl]benzamide derivatives. The convenient synthesis method for the amide ligands, together with their operationally simple complexation by direct C–H auration, permitted changes to both the steric and electronic properties of Au(III) complexes for promoting the catalytic three-component couplings of an aldehyde, an amine, and an alkyne.

Key words

gold(III) complexes - ligands - pincer complexes - catalysts - multicomponent reactions - chiral complexes

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References

References and Notes
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12 Au(III) Complexes 2a–l; General Procedure A sealed tube was charged with amide 1 (0.1 mmol), NaAuCl₄·2 H₂O (39.8 mg, 0.1 mmol), potassium pivalate (19.6 mg, 0.2 mmol), MeCN (2 mL), and H₂O (2 mL). The mixture was stirred overnight at 80 °C and then cooled to r.t. The precipitate was collected by filtration, washed with MeOH, and dried in vacuo. Complex 2a Yellowish-brown solid; yield: 31.1 mg (65%); mp 308.3–309.8 ℃. IR (ATR): 2945, 1647, 1625, 1579, 1504, 1463, 1400, 1381 cm^–1. ¹H NMR (CDCl₃, 400 MHz): δ = 9.14 (d, J = 5.2 Hz, 1 H), 9.03 (d, J = 7.6 Hz, 1 H), 8.48 (d, J = 8.4 Hz, 1 H), 7.82 (d, J = 7.6 Hz, 1 H), 7.65–7.71 (m, 2 H), 7.54 (dd, J = 1.6, 7.6 Hz, 1 H), 7.50 (d, J = 7.2 Hz, 1 H), 7.34 (ddd, J = 1.2, 7.6, 7.6 Hz, 1 H), 7.29 (dd, J = 1.6, 8.0 Hz, 1 H). ¹³C NMR (100.5 MHz, CDCl₃): δ = 174.53, 146.56, 144.90, 144.02, 142.18, 141.19, 139.31, 132.42, 131.04, 130.76, 130.67, 130.41, 128.85, 121.91, 121.41, 120.91. HRMS (FD): m/z [M]⁺ calcd for C₁₆H₁₀AuClN₂O: 478.0147; found: 478.0129. Au(III) Complex 4 In a glove box, a vial equipped with a magnetic stirring bar was charged with complex 2a (47.9 mg, 0.1 mmol), 2,2-diphenylpent-4-en-1-ol (3; 47.7 mg, 0.2 mmol), AgBF₄ (19.5 mg, 0.1 mmol), and CH₂Cl₂ (1 mL), and the mixture was stirred for 14 h at r.t. The solvent was removed under reduced pressure, and the crude product was purified by flash chromatography [silica gel, gradient elution hexane to hexane–EtOAc (9:1)] to give a yellow solid; yield: 31.1 mg (65%); mp 275.8–277.5°C. IR (ATR): 2972, 1625, 1582, 1502, 1466, 1394 cm^–1. ¹H NMR (400 MHz, CDCl₃): δ = 8.97 (dd, J = 1.2, 8.4 Hz, 1 H), 8.61 (dd, J = 1.6, 5.2 Hz, 1 H), 8.40 (dd, J = 1.2, 8.4 Hz, 1 H), 7.71–7.75 (m, 1 H), 7.65 (dd, J = 8.0, 8.0 Hz, 1 H), 7.52 (dd, J = 5.2, 8.4 Hz, 1 H), 7.36–7.40 (m, 2 H), 7.28–7.32 (m, 2 H), 7.20–7.28 (m, 9 H), 7.12–7.19 (m, 1 H), 4.59 (ddt, J = 6.4, 6.8, 8.0 Hz, 1 H), 4.44 (d, J = 8.8 Hz, 1 H), 4.39 (d, J = 8.8 Hz, 1 H), 2.88 (dd, J = 6.8, 12.4 Hz, 1 H), 2.59 (dd, J = 8.0, 12.4 Hz, 1 H), 2.00 (d, J = 6.4 Hz, 2 H). ¹³C NMR (100.5 MHz, CDCl₃): δ = 173.39, 146.51, 146.46, 146.08, 144.72, 140.57, 135.52, 131.33, 130.60, 129.95, 128.95, 128.41, 128.37, 127.63, 127.26, 127.07, 126.36, 126.25, 121.42, 121.14, 119.51, 80.28, 56.58, 47.57, 34.88. HRMS (ESI): m/z [M + H]⁺ calcd for C₃₃H₂₈AuN₂O₂: 681.1811; found: 681.1827. Alkynyl Au(III) Complex 6s In a glove box, a vial equipped with a magnetic stirring bar was charged with complex 2a (47.9 mg, 0.1 mmol), phenylacetylene (5; 12.3 mg, 0.12 mmol), CuI (22.9 mg, 0.12 mmol), Et₃N (12.1 mg, 0.12 mmol), and CH₂Cl₂ (1 mL), and the mixture was stirred for 14 h at r.t. Workup as above gave a yellow solid; yield: 43.8 mg (81%); mp 290.6–293.5 ℃. IR (ATR): 3053, 2989, 1640, 1594, 1582, 1501, 1487, 1462, 1450, 1441, 1384 cm^–1. ¹H NMR (400 MHz, CDCl₃): δ = 9.24 (dd, J = 1.2, 4.8 Hz, 1 H), 9.02 (dd, J = 1.6, 8.4 Hz, 1 H), 8.50 (dd, J = 1.2, 8.4 Hz, 1 H), 7.94 (dd, J = 1.6, 8.0 Hz, 1 H), 7.65–7.72 (m, 2 H), 7.59–7.64 (m, 3 H), 7.49 (dd, J = 1.2, 8.0 Hz, 1 H), 7.26–7.40 (m, 5 H). ¹³C NMR (100.5 MHz, CDCl₃): δ = 174.94, 148.32, 146.40, 145.12, 144.47, 140.95, 136.20, 133.78, 132.28, 131.84, 131.26, 130.77, 130.04, 128.30, 128.23, 127.51, 125.35, 121.92, 121.70, 120.35, 97.94, 96.44. HRMS (ESI): m/z [M + H]⁺ calcd for C₂₄H₁₆AuN₂O: 545.0923; found: 545.0937. A³ Reaction; General Procedure A vial equipped with a magnetic stirring bar was charged with the appropriate complex 2 (0.005 mmol), 4-bromobenzaldehyde (7; 18.5 mg, 0.1 mmol), piperidine (8; 9.4 mg, 0.11 mmol), and phenylacetylene (5; 15.3 mg, 0.15 mmol). H₂O (0.2 mL) was added, and the resulting suspension was stirred for 24 h at 40 ℃ then cooled to r.t. The mixture was extracted with EtOAc (×3) and the combined organic layers were dried (MgSO₄). The yield was determined by ¹H NMR analysis with 1,1,2,2-tetrachloroethane as internal standard.

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