Straightforward synthesis of quinolines from enones and 2-aminobenzyl alcohols using an iridium-catalyzed transfer hydrogenative strategy

Abstract

A new protocol for the direct synthesis of quinolines from enones and 2-aminobenzyl alcohols via iridium-catalyzed transfer hydrogenative reactions has been demonstrated. This method employs easily available [IrCp*Cl2]2/t-BuOK as the efficient catalyst system, proceeding with the merits of high step- and atom efficiency, mild reaction conditions and operational simplicity. The experimental studies suggest that the reactions start with transfer hydrogenation, followed by the Friedländer reaction to give the final products.

Determination of 2-Acetyl-1-pyrroline via a Color-Change Reaction Using Chromium Hexacarbonyl

“…The reaction of 2-aminobenzaldehyde with the fragrant rice grain extract in DCM exhibited a similar absorbance (λ max = 423 nm) as the synthetic 2AP (λ max = 427 nm), as expected, but the intensity was low. Note that 2-aminobenzaldehyde is an expensive and unstable reagent that must be stored below −20 • C [20]. By contrast, Cr(CO) 6 is inexpensive, stable at room temperature, and dissolves effectively in various organic solvents.…”

Iridium-Catalyzed Transfer Hydrogenation for Construction of Quinolines from 2-Aminobenzyl Alcohols with Enones in Water

“…3-Benzyl-2-phenyl-quinoline (3aa): [34] 3-Benzyl-2-p-tolyl-quinoline (3aj): [34] 3-Benzyl-2-(4-chloro-phenyl)-quinoline (3ak): [34] white solid, mp 91-92 o C, Yield: 315.9 mg, 96%. 1…”

“…All rights reserved. 3-Benzyl-2-furan-2-yl-quinoline (3al): [34] brown solid, mp 74- 2-(3-Chloro-phenyl)-3-methyl-quinoline (3am): [35] white solid, mp 81-82 o C, Yield: 232.9 mg, 92%. 1 3-Methyl-2-m-tolyl-quinoline (3aq): [35] white solid, mp 41-42 o C, Yield: 207.5 mg, 89%.…”

“…(101 MHz, CDCl3) δ 160.71, 146.56, 140.55, 139.94, 137.10, 132.54, 129.25, 129.22, 129.02, 128.87, 128.51, 128.32, 128.32, 128.24, 127.53, 127.13, 126.54, 126.28, 39.11.3-(2-Methoxy-benzyl)-2-phenyl-quinoline (3ab):[34] yellow solid, mp 81-82 o C, Yield: 302.4 mg, 93%.1 H NMR (400 MHz, CDCl3) δ 8.14 (s, 1H), 7.82 (s, 1H), 7.67 (dd, J = 16.1, 6.3 Hz, 1H), 7.56 (s, 2H), 7.45 (d, J = 7.1 Hz, 4H), 7.22 (d, J = 7.5 Hz, 1H), 6.88 (d, J = 28.5 Hz, 3H), 4.09 (s, 2H), 3.69 (s, 3H); 13 C NMR (101 MHz, CDCl3) δ 160.82, 157.25, 146.45, 140.84, 136.48, 132.50, 130.3-Benzyl-2-(2,6-dimethyl-phenyl)-quinoline (3ae): colorless oil, Yield: 290.9 mg, 90%. 1 H NMR (400 MHz, CDCl3) δ 8.14 (d, J = 8.5 Hz, 1H), 7.68-7.45 (m, 8H), 7.36 (s, 1H), 7.18-7.07 (m, 3H), 4.02 (s, 2H), 2.16 (s, 6H); 13 C NMR (101 MHz, CDCl3) δ 160…”

Cascade Reaction of α, β‐Unsaturated Ketones and 2‐Aminoaryl Alcohols for the Synthesis of 3‐Acylquinolines by a Copper Nanocatalyst

“…Generally, 2‐aminobenzyl alcohols as synthetic materials are more stable and cheaper than the relevant aldehydes, and a great diversity of α, β‐unsaturated ketones are easily available. In our previous work, we realized the synthesis of quinolines from α, β‐unsaturated ketones and 2‐aminobenzyl alcohols using an iridium‐catalyzed transfer hydrogenation strategy [14] . With our continuous interest in the design of non‐noble metal catalysts as well as the construction of quinolones, [15] we were therefore motivated to develop a new method to synthesize 3‐acylquinolines by employing heterogeneous catalysts.…”