Dehydrogenative Coupling of Alkylamines with Primary Alcohols Forming α-Amino Ketones.

Acceptorless dehydrogenative coupling reactions between C-H bonds offer straightforward and atom-economical methods connecting readily available materials while liberating gaseous hydrogen as the sole byproduct. Despite the growing interest in such transformations, their realization still poses a significant challenge. Here we report a photoinduced dehydrogenative coupling reaction of alkylamines with primary alcohols. C-H bonds adjacent to nitrogen and oxygen are site-selectively cleaved, and a C-C bond is created between the carbon atoms in a cross-selective manner to produce α-amino ketones. Diverse polar functionalities such as esters, amides, and carboxylic acids survived, demonstrating the broad applicability of the present method.

Dehydrogenative Coupling of Benzylic and Aldehydic C-H Bonds.

A photoinduced dehydrogenative coupling reaction between benzylic and aldehydic C-H bonds is reported. When a solution of an alkylbenzene and an aldehyde in ethyl acetate is irradiated with visible light in the presence of iridium and nickel catalysts, a coupled α-aryl ketone is formed with evolution of dihydrogen. An analogous C-C bond forming reaction occurs between a C-H bond next to the nitrogen of an N-methylamide and an aldehydic C-H bond to produce an α-amino ketone. These reactions provide a straightforward pathway from readily available materials leading to valued structural motifs of pharmacological relevance.

Photoinduced Specific Acylation of Phenolic Hydroxy Groups with Aldehydes.

A convenient method is reported to specifically acylate phenolic hydroxyl groups through a radical pathway. When a mixture of an aldehyde and a phenol in ethyl acetate is irradiated with blue light in the presence of iridium and nickel bromide catalysts at ambient temperature, phenoxyl and acyl radicals are transiently generated in situ and cross-couple to furnish an ester. Aliphatic hydroxy groups remain untouched under the reaction conditions.

2-Arylsilacyclobutane as a Latent Carbanion Reacting with CO2.

An electronically neutral 2-arylsilacyclobutane generates a nucleophilic carbanion at room temperature through cleavage of the benzylic C-Si bond when simply dissolved in polar aprotic solvents such as N,N-dimethylformamide (DMF). The nucleophilic species is capable of capturing carbon dioxide to furnish a silalactone. The carboxylation reaction is unique in that no additional activating agents are required.

Visible-Light-Driven Dehydrogenative Coupling of Primary Alcohols with Phenols Forming Aryl Carboxylates.

A preparative method for obtaining aryl esters from aliphatic primary alcohols and phenols was developed. The reaction proceeds under the irradiation of visible light at ambient temperature, dispensing with any oxidant or hydrogen acceptor. Primary alcohols having a variety of functional groups are successfully esterified with phenols. The produced esters can be utilized as the precursor of various carbonyl compounds.

Synthetic Approach to Benzocyclobutenones Using Visible Light and a Phosphonate Auxiliary.

Reported herein is a two-step procedure to synthesize benzocyclobutenones from (o-alkylbenzoyl)phosphonates. It consists of a visible-light-driven cyclization reaction forming phosphonate-substituted benzocyclobutenols and subsequent elimination reaction of the H-phosphonate, which assumes a key role as the recyclable auxiliary. A wide variety of functionalized benzocyclobutenones, which include those difficult to synthesize by conventional methods, are efficiently synthesized.