Synthesis of alkenylphosphine oxides via Tf2O promoted addition-elimination of ketones and secondary phosphine oxides.

Herein, we describe an efficient method for the synthesis of alkenylphosphine oxides via a Tf2O promoted addition-elimination process. Various diarylphosphine oxides and alkylarylphosphine oxides react with ketones smoothly and produce alkenylphosphine oxides in moderate to excellent yields with abundant functional group compatibility. In addition, several transformations and applications of the product also demonstrate the potential value of the methodology.

Dual Photoredox/Nickel-Catalyzed Dehydrative Difluoroalkylation of Benzyl Alcohols for the Synthesis of Allylic gem-Difluorides.

A photoredox/Lewis acid cooperative catalytic system has been developed for the construction of Cvinyl-CRf bonds through the dehydrative difluoroalkylation of benzyl alcohols. A variety of allylic gem-difluorides could be obtained in moderate yields with good to excellent E/Z selectivity. In addition, several control experiments have been explored, and a possible mechanism was proposed for this process.

Copper-Catalyzed Asymmetric Cyanation of Propargylic Radicals via Direct Decarboxylation of Propargylic Carboxylic Acids.

Chiral propargylic cyanides are often used as small-molecule feedstocks for the introduction of chiral centers into various valuable products and complex molecules. Here, we have developed a highly atom-economical strategy for the chiral copper complex-catalyzed synthesis of chiral propargylic cyanides. Propargylic radicals can be smoothly obtained by direct decarboxylation of the propargylic carboxylic acids without preactivation. The reactions show excellent selectivity and functional group compatibility. Gram-scale reaction and several conversion reactions from chiral propargylic cyanide have demonstrated the synthetic value of this strategy.

Copper-Catalyzed 1,2-Dicarbonylative Cyclization of Alkenes with Alkyl Bromides via Radical Cascade Process.

Herein, we developed a new procedure on 1,2-dicarbonylative cyclization of 4-aryl-1-butenes with alkyl bromides. Using simple copper catalyst, two molecules of carbon monoxide were introduced into the double bond with the formation of four new C-C bonds and a new ring. Various α-tetralones and 2,3-dihydroquinolin-4-ones were formed in moderate to good yields.

Copper-Catalyzed Substrate-Controlled Carbonylative Synthesis of α-Keto Amides and Amides from Alkyl Halides.

Controllable production of α-keto amides and amides from the same substrates is an attractive goal in the field of transition-metal-catalyzed (double-)carbonylation. Herein, a novel copper-catalyzed highly selective double carbonylation of alkyl bromides has been developed. Moderate to good yields of α-keto amides were obtained as the only products. In the case of alkyl iodides, double- and mono-carbonylation can be achieved controllably under different conditions.

Copper-catalyzed enantioselective carbonylation toward α-chiral secondary amides.

Secondary amides are omnipresent structural motifs in peptides, natural products, pharmaceuticals, and agrochemicals. The copper-catalyzed enantioselective hydroaminocarbonylation of alkenes described in this study provides a direct and practical approach for the construction of α-chiral secondary amides. An electrophilic amine transfer reagent possessing a 4-(dimethylamino)benzoate group was the key to the success. This method also features broad functional group tolerance and proceeds under very mild conditions, affording a set of α-chiral secondary amides in high yields (up to 96% yield) with unprecedented levels of enantioselectivity (up to >99% ee). α,ß-Unsaturated secondary amides can also be produced though the method by using alkynes as the substrate.

NHC ligand-powered palladium-catalyzed carbonylative C-S bond cleavage of vinyl sulfides: efficient access to tert-butyl arylacrylates.

A method for palladium-catalyzed carbonylative C-S bond activation of divinyl sulfides to synthesize numerous tert-(E)-butyl arylacry-lates under 1 bar of CO has been developed. Employing electron-rich NHC as the ligand, the electron-rich and stabilized palladium complex trend to oxidative addition to the relatively inert C-S bond and decreased the poisoning effect of sulfide and CO; a series of tert-(E)-butyl acrylates were obtained in moderate to good yields.

Rhodium-Catalyzed Carbonylative Synthesis of Aryl Salicylates from Unactivated Phenols.

A rhodium-catalyzed carbonylative transformation of unactivated phenols to aryl salicylates is described. This protocol is characterized by utilizing 1,3-rhodium migration as the key step to provide direct access to synthesize o-hydroxyaryl esters. Various desired aryl o-hydroxybenzoates were produced in moderate to excellent yields with bis(dicyclohexylphosphino)ethane (DCPE) as the ligand. Interestingly, diphenyl carbonate was formed as the main product when 1,3-bis(diphenylphosphino)propane (DPPP) was used as the ligand. A plausible reaction mechanism is proposed.

Deaminative carbonylative coupling of alkylamines with styrenes under transition-metal-free conditions.

A transition-metal-free deaminative carbonylation of alkylamines with styrenes has been developed. The reaction shows good functional group compatibility and various α,ß-unsaturated ketones were obtained in moderate to good yields. The alkyl radical generated from Katritzky salts via base-promoted C-N bond cleavage is one of the key intermediates in this reaction.

Nucleophilic Aromatic Substitution of Unactivated Aryl Fluorides with Primary Aliphatic Amines by Organic Photoredox Catalysis.

In this work, a mild and transition-metal-free approach for the nucleophilic aromatic substitution (SN Ar) of unactivated fluoroarenes with primary aliphatic amines to form aromatic amines is reported. This reaction is facilitated by the formation of cationic fluoroarene radical intermediates in the presence of an acridinium-based organic photocatalyst under blue-light irradiation. Various electron-rich and electron-neutral fluoroarenes are competent electrophiles for this transformation. A wide range of primary aliphatic amines, including amino acid esters, dipeptides, and linear and branched amines are suitable nucleophiles. The synthetic utility of this protocol is demonstrated by the late-stage functionalization of several complex drug molecules.

Ruthenium-Catalyzed Carbonylative Coupling of Anilines with Organoboranes by the Cleavage of Neutral Aryl C-N Bond.

Herein, we report the first ruthenium-catalyzed Suzuki-type carbonylative reaction of electronically neutral anilines via C(aryl)-N bond cleavage. Without any ligand and base, diaryl ketones can be obtained in moderate to high yields by using Ru3(CO)12 as the catalyst and chelation assisted by pyridine. The pyridine ring has a significant effect on both high efficiency and high regioselectivity in the cleavage of the aryl C-N bond in anilines.

Photocatalytic Hydrogen-Evolving Cross-Coupling of Arenes with Primary Amines.

Herein, we described a cooperative catalyst system consisting of an acridinium photoredox catalyst and a cobalt-based proton-reduction catalyst that is effective for the C-H amination of arenes with concomitant generation of hydrogen. This oxidant-free method allows a variety of amines with diverse functional groups to be converted to aromatic amines. Additionally, this protocol can also be extended to hydrolytically unstable benzophenone imines.

Mild dynamic kinetic resolution of amines by coupled visible-light photoredox and enzyme catalysis.

Herein, we described photoenzymatic dynamic kinetic resolution (DKR) of amines under mild conditions. The racemization of amines via a photoredox-mediated hydrogen atom transfer (HAT) protocol in conjunction with an enzyme catalyst to achieve the DKR of amines allows a variety of primary amines to be converted into a single enantiomer in high yield and with excellent enantioselectivity. Notably, this protocol can also be extended to 1,4-diamine derivatives with high levels of diastereo- and enantioselectivity.