Cu(II) bromide catalyzed oxidation of aldehydes and alcohols

Abstract

A variety of aromatic, aliphatic and conjugated aldehydes and alcohols were transformed to the corresponding carboxylic acids and ketones with a quantitative conversion in high yields with 70% t-BuOOH solution in water in the presence of catalytic (5 mol%) amounts of CuBr 2 under room temperature conditions. The conversion of 4-methoxybenzaldehyde to 4-methoxybenzoic acid is extremely facile in MeCN at ambient temperature in the presence of 5 mol% CuBr 2 and 2 equiv. 70% t-BuOOH (water) as the oxidant. Oxidation with t-BuOOH (water) alone in MeCN was found to be negligible. The scope of our catalytic system is applicable for a wide range of aromatic, conjugated and aliphatic substrates. These aldehydes were converted to the corresponding carboxylic acids in good isolated yields in reasonable times. It is pertinent to mention here that mild halogenic oxidants like hypochlorites, chlorites and NBS are not suitable for substrates with electron-rich aromatic rings, olefinic bonds and secondary hydroxyl groups. Substitutions at different positions on the phenyl ring do not hinder the reaction, although the reaction time is affected. Oxidation of α,β unsaturated derivatives resulted in the formation of the expected acid in good yield. In addition, the transformation of secondary alcohols to ketones is extremely facile. No recemization was observed for menthone. This method possesses a wide range of capabilities since it can be used with other functional groups which may not tolerate oxidative conditions, involves fairly simple method for work-up, exhibits chemoselectivity and proceeds under ambient conditions. The resulting products are obtained in good yields within reasonable time.

Nonthermal Plasma‐Induced Degradation of Morin and Enhancement of Biological Activities

“…Therefore, new methoxylated benzofuranone 1 was assigned the trivial name moriplasmin ( Figure ). The isolated known compounds were identified as 2‐(2,4‐dihydroxybenzoyl)‐2,4,6‐trihydroxy‐1‐benzofuran‐3(2 H )‐one ( 2 ) and β ‐resorcylic acid ( 3 ) by comparison of the spectroscopic data with available literature values.…”

“…White amorphous powder. 1 H‐NMR (CD 3 OD, 600 MHz): 7.50 (1H, d, J =8.4, H‐6), 6.27 (1H, dd, J =8.4, 1.8, H‐5), 6.19 (1H, d, J =1.8, H‐3) . FAB‐MS: m/z 155 [M+H] + .…”

6,7-Dimethoxy-2-phenethyl-1,2,3,4-tetrahydroisoquinoline amides and corresponding ester isosteres as multidrug resistance reversers

“…ethanol/petroleum ether. 42 To a stirred solution of CuBr 2 (0.04 mmol) and 2-methoxy-1-naphthaldehyde (0.80 mmol) in 3.0 ml of an CH 3 CN was added 70% t-BuOOH in water (1.60 mmol). When all the aldehyde had been consumed, the solvent was removed under reduced pressure.…”

“…Most of the carboxylic acids were commercially available. 2-Methoxy-1-naphthoic acid 29 was synthetised starting from the corresponding aldehyde, following the general procedure described by Das 42 (Scheme 3), while 2,3-dimethoxy-1naphthoic acid 30 was obtained from the corresponding aldehyde as described by Ohnmacht 43 (Scheme 3). 6-Methoxyquinoline-4carboxylic acid 31 was synthesised following the procedure described by Kowanko 44 (Scheme 4).…”

Selective aerobic oxidation of alcohols catalyzed by iron chloride hexahydrate/TEMPO in the presence of silica gel

“…Numerous reports describe aerobic alcohol oxidation using transition metals such as Cu, Pd, Ru, Au, or V, alone or in conjugation with the nitroxy radical 2,2,6,6‐tetramethylpiperidine N ‐oxyl (TEMPO) as catalysts. In these studies, noble metals, halogens, extra bases or complicated ligands are often used.…”