CuCl-catalyzed aerobic oxidation of 2,3-allenols to 1,2-allenic ketones with 1:1 combination of phenanthroline and bipyridine as ligands

Abstract

SummaryA protocol has been developed to prepare 1,2-allenyl ketones using molecular oxygen in air or pure oxygen as the oxidant from 2,3-allenylic alcohols with moderate to good yields under mild conditions. In this reaction CuCl (20 mol %) with 1,10-phenanthroline (10 mol %) and bipyridine (10 mol %) was used as the catalyst. It is interesting to observe that the use of the mixed ligands is important for the higher yields of this transformation: With the monoligand approach developed by Markó et al., the yields are relatively lower.

Lewis Acid-Mediated Cyclization of Allenyl Aryl Ketones

“…1 H NMR (500 MHz, CDCl 3 ): δ 8.05 (1H, d, J = 8.2 Hz), 7.90 (1H, d, J = 8.2 Hz), 7.85 (1H, d, J = 7.8 Hz), 7.56 (1H, d, J = 7.1 Hz), 7.53–7.46 (2H, m), 7.42 (1H, t, J = 7.6 Hz), 4.79 (2H, broad s), 2.09 (3H, broad s); 13 C­{ 1 H} NMR (126 MHz, CDCl 3 ): δ 218.6, 197.6, 136.9, 133.5, 130.7, 130.5, 128.3, 127.0, 126.6, 126.1, 125.4, 124.0, 104.9, 78.3, 13.9; HRMS (ESI-TOF) m / z : [M + Na] + calcd for C 15 H 12 ONa, 231.0780; found, 231.0784. NMR spectra are in accord with the literature …”

“…NMR spectra are in accord with the literature. 35 2-Methyl-1-(pyren-1-yl)buta-2,3-dien-1-one (23b). Alcohol 23a (260 mg, 0.915 mmol) and IBX (0.351 g, 1.25 mmol) in DMSO (2.5 mL) gave 23b (172 mg, 67%) as an oil.…”

Mechanistic Studies on a Cooperative NHC Organocatalysis/Palladium Catalysis System: Uncovering Significant Lessons for Mixed Chiral Pd(NHC)(PR3) Catalyst Design

“…The combination of achiral ligand and chiral ligand has been reported to improve the reactivity and enantioselectivity in many transition-metal-catalyzed reactions. − The Ding group showed elegant studies that achiral phosphines strongly enhance the results of hydrogenation of β,β-diarylacrylic acids and α-CF 3 - or β-CF 3 -substituted acrylic acids . Inspired by these works, we continued to investigate the real role of PPh 3 in the present reaction.…”

CuCl‐Catalyzed Aerobic Oxidation of Allylic and Propargylic Alcohols to Aldehydes or Ketones with 1:1 Combination of Phenanthroline and Bipyridine as the Ligands

“…Based on our previously reported conditions, [23] several other solvents were firstly screened using cinnamyl alcohol 1a as the substrate (Table 1, entries 1 to 5). Still toluene was the best choice considering both the reaction time and yield.…”

“…[22] We previously reported the CuCl-catalyzed aerobic oxidation of 2,3-allenols by applying a modified protocol using mixed ligands [23] based on Markó's work. The combination of phen and bpy as the ligands showed high efficiency and required lower temperature of only 35 ℃.…”