4,5-Dioxo-imidazolinium Cation Activation of 1-Acyl-1-carbamoyl Oximes: Access to Cyanoformamides Using Dichloroimidazolidinedione

DCID-mediated esterification of carboxylic acids with alcohols under mild conditions

DCID (Dichloroimidazolidinedione) 2 is used as a novel coupling reagent for the esterification of carboxylic acids with alcohols at room temperature. The reaction represents the first DCID-promoted esterification under mild conditions with good to excellent yields. Reactions can proceed smoothly with those bearing electron-withdrawing and donating group(s) on the carboxylic acids and benzyl alcohols at ambient temperature. Furthermore, we proposed a plausible mechanism and confirmed it by isolating and characterizing intermediates 3a and 7. The structures of the synthesized compounds were confirmed by comparison of melting points and NMR spectra.

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.

Synthesis of Acyl Fluorides via DAST-Mediated Fluorinative C-C Bond Cleavage of Activated Ketones

A new protocol for preparation of acyl fluorides was developed by recognizing activated ketones as starting materials. The method provides a different scope compared with previously reported methods that employ carboxylic acids as substrates. A working hypothesis of pull-and-push-driven fluorinative C-C bond cleavage was successfully demonstrated by the simple addition of diethylaminosulfur trifluoride (DAST) derivatives to α-oximinoketones. The designed reaction system led to a highly efficient and chemoselective reaction. The wide availability of the ketones allowed for a range of synthetically useful aryloyl and aliphatic acyl fluorides including those containing chiral skeletons. The method is mild, fast, scalable, and potentially one-pot operative.