Aerobic oxidation of aldehydes to acids in water with cyclic (alkyl)(amino)carbene copper under mild conditions

Chemoselective oxidation of aromatic aldehydes to carboxylic acids: potassium tert-butoxide as an anomalous source of oxygen

Chemoselective oxidation of aromatic and heteroaromatic aldehydes (>45 examples) to their corresponding carboxylic acids has been developed. Potassium tert-butoxide acts as an oxygen source during this transformation that delivers the corresponding acids without chromatographic purifications. The use of bench-top reagents, operational simplicity, and high level of chemo-selectivity with respect to oxidation of the least preferred aldehyde functionality, in the presence of more susceptible functional groups, are some of the highlights of this strategy.

Understanding cyclic(alkyl)(amino)carbene-copper complex catalysed N-H and O-H bond addition to electron deficient olefins

The hydroamination of electron-deficient olefins was carried out using the (CAAC)Cu-Cl (CAAC = cyclic (alkyl)(amino)carbene) catalyst with an excellent yield at room temperature and under an open atmosphere. Furthermore, the catalyst shows excellent efficiency in the hydroaryloxylation and hydroalkoxylation of alkenes under mild conditions. The efficiency of the catalyst was tested for a wide range of substrates with different electronic and steric functionalities. Detailed computational studies have been carried out to understand the mechanism of these Cu(I) catalyzed reactions, which revealed that the reaction proceeds via either a four-membered or a six-membered cyclic transition state containing the copper ion.

Realizing 1,1-Dehydration of Secondary Alcohols to Carbenes: Pyrrolidin-2-ols as a Source of Cyclic (Alkyl)(Amino)Carbenes

Herein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-CuI -complexes and cyclic thiones when reacted with CuI -salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based CuI -salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH2 ) by 1,1-dehydration of methanol. Addressed is also the reactivity of water towards CAACs, which proceeds through an oxidative addition of the O-H bond to the carbon(II)-center. This emphasizes the ability of carbon-compounds to mimic the reactivity of transition-metal complexes: reversible oxidative addition and reductive elimination of the O-H bond to/from the C(II)/C(IV)-centre.

Selective oxidation of aldehydes by oxygen over macroporous alkaline resin

In this reaction, the oxidation of aldehydes is selectively catalyzed by basic resin D201-OH for the first time. Moreover, mild and high-yield oxidation of aldehydes can be achieved without any cocatalyst.