Transition-Metal-Free Conversion of Trifluoropropanamides into Cyanoformamides through C–CF3 Bond Cleavage and Nitrogenation

Carbon-carbon triple bond cleavage and reconstitution to achieve aryl amidation using nitrous acid esters

C-C bond cleavage and recombination provide an efficient strategy for the modification and reconstruction of molecule structures. Herein, we present a method for achieving amidation of aryl C(sp2)-H bond through the cleavage and recombination of C-C triple bond with the involvement of nitrous acid esters. This method marks the instance of precise and controlled stepwise cleavage of C-C triple bond, offering a fresh perspective for the cleavage of such bonds. Nitrous acid ester serves as both a radical source and a hydrogen atom transfer (HAT) reagent to functionalize and utilize the two carbon atoms of the C-C triple bond. The alkoxy radical captures the hydrogen atom from the aryl C(sp2)-H bond or N-hydroxyl to induce the 1,3-oxygen radical migration, which is crucial for the subsequent cleavage of the C-C bond.

Cu-Catalyzed Carbocyclization for General Synthesis of N-Containing Heterocyclics Enabled by BrCF2COOEt as a C1 Source

A practical and efficient copper-catalyzed carbocyclization of 2-functionalized anilines with ethyl bromodifluoroacetate has been developed. Ethyl bromodifluoroacetate is employed as the C1 source via quadruple cleavage in this transformation. This reaction can afford a variety of N-containing heterocyclics with satisfactory yields and excellent functional group compatibility.

Amine-Induced Selective C-C Bond Cleavage of 2,2,2-Trifluoroethyl Carbonyls for the Synthesis of Ureas and Amides

An efficient and selective transformation of 2,2,2-trifluoroethyl carbonyls into ureas/amides with amines is reported. This protocol allows the selective cleavage of the C-C bond of 2,2,2-trifluoroethyl carbonyls under transition metal-free and oxidant-free conditions, which is in contrast to the analogous C-F or C-CF₃ bond functionalization. This reaction reveals the unexplored reactivity of 2,2,2-trifluoroethyl carbonyls and exhibits a broad substrate range and good functional group tolerance.

Reductive Cleavage of C(sp2)-CF3 Bonds in Trifluoromethylpyridines

A reductive detrifluoromethylation protocol has been developed making use of an earth-abundant alkoxide base and silicon hydride species. A variety of pyridine and quinoline substrates bearing alkyl, aryl, and amino functional groups are reduced in moderate to high yields. The reaction is chemoselective for C(sp²)-CF₃ groups located at the 2-position on the pyridine ring, leaving trifluoromethyl groups located elsewhere on the molecule intact. Preliminary mechanistic studies demonstrate that the combination of silane and base generates a strongly reducing system that may transfer an electron to electron-deficient π systems.

Iodine-DMSO mediated conversion of N-arylcyanothioformamides to N-arylcyanoformamides and the unexpected formation of 2-cyanobenzothiazoles

Cyanoformamides are ubiquitous as useful components for assembling key intermediates and bioactive molecules. The development of an efficient and simple approach to this motif is a challenge. Herein, we demonstrate the effectiveness of the I₂-DMSO oxidative system in the preparation of N-arylcyanoformamides from N-arylcyanothioformamides. The synthetic method features mild conditions, broad substrate scope, and high reaction efficiency. Furthermore, this method provides an excellent entry to exclusively afford 2-cyanobenzothiazoles which are useful substrates to access new luciferin analogs. The structures of all new products were elucidated by multinuclear NMR spectroscopy and high accuracy mass spectral analysis. Crystal-structure determination by means of single-crystal X-ray diffraction was carried out on (4-bromophenyl)carbamoyl cyanide, 5,6-dimethoxybenzo[d]thiazole-2-carbonitrile, 5-(benzyloxy)benzo[d]oxazole-2-carbonitrile, 4,7-dimethoxybenzo[d]thiazole-2-carbonitrile, and (5-iodo-2,4-dimethoxyphenyl)carbamoyl cyanide, a key intermediate with mechanistic implications.

Conversion of N-arylcyanothioformamides to N-arylcyanoformamides and 2-cyanobenzothiazoles has been achieved with I₂-DMSO oxidative system.

Electrochemical Synthesis of Cyanoformamides from Trichloroacetonitrile and Secondary Amines Mediated by the B12 Derivative

The B₁₂ derivative, heptamethyl cobyrinate, -mediated electrochemical synthesis of cyanoformamides has been developed. Aerobic oxygenation of the carbon-centered radical initiated in situ generation of the reactive acyl chloride intermediate, which led to cyanoformamides in the presence of an amine. This one-pot and scalable synthetic method has been demonstrated with 41 examples up to 94% yields with 21 new compounds. The mechanism of electrolysis mediated by the B₁₂ derivative has been proposed based on the DFT calculations.

Palladium-catalyzed selective defluorinative arylation for the efficient stereospecific synthesis of (E)-β-fluoroacrylamides

A practical and efficient method for the synthesis of (E)-β-fluoroacrylamides was developed by the selective defluorinative arylation of trifluoropropanamides with arylboronic acids.

Copper-Catalyzed Selective Defluorinative Sulfuration of Trifluoropropanamides Leading to α-Fluorothioacrylamides

A practical and efficient method for the synthesis of α-fluorothioacrylamide was developed from selective defluorinative sulfuration of trifluoropropanamides with disulfides. The N-chelation-assisted copper-catalyzed defluorination and sulfurization reactions feature excellent functional group tolerance and incorporation of both sulfur atoms of disulfides into acrylamides.