Solvent-Free Synthesis of Cyanoformamides from Carbamoyl Imidazoles

From dithiocarbamates to branched dithiocarbazates: Compounds with potent antischistosomal activity

Schistosomiasis or bilharzia is caused by blood flukes of the genus Schistosoma and represents a considerable health and economic burden in tropical and subtropical regions. The treatment of this infectious disease relies on one single drug: praziquantel (PZQ). Therefore, new and potent antischistosomal compounds need to be developed. In our previous work, starting with the drug disulfiram, we developed dithiocarbamates with in vitro antischistosomal activities in the low micromolar range. Based on these results, we report in this study on the synthesis and biological testing of the structurally related dithiocarbazates against Schistosoma mansoni, one of the major species of schistosomes. In total, three series of dithiocarbazate derivatives were examined, and we found that the antischistosomal activity of N-unbranched dithiocarbazates increased by further N-substitution. Comparable tetra-substituted dithiocarbazates were rarely described in the literature, thus a synthesis route was established. Due to the elaborate synthesis, the branched dithiocarbazates (containing an N-aminopiperazine) were simplified, but the resulting branched dithiocarbamates (containing a 4-aminopiperidine) were considerably less active. Taken together, dithiocarbazate-containing compounds with an in vitro antischistosomal activity of 5 µM were obtained.

A versatile way for the synthesis of monomethylamines by reduction of N-substituted carbonylimidazoles with the NaBH4/I2 system

An economical and versatile protocol for the one-pot synthesis of monomethylamines by reduction of N-substituted carbonylimidazoles with NaBH₄/I₂ in THF at reflux temperature is described. This method used no special catalyst and various monomethylamines can be easily obtained in moderate to good yields from a wide range of raw materials including amines (primary amines and secondary amines), carboxylic acids and isocyanates. Besides, an interesting reduction selectivity was observed. Exploration of the reaction process shows that it undergoes a two-step pathway via a formamide intermediate and the reduction of the formamide intermediate to monomethylamine as the rate-determining step. This work can contribute significantly expanding the applications of N-substituted carbonylimidazoles.

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.

The synthesis of cyanoformamides via a CsF-promoted decyanation/oxidation cascade of 2-dialkylamino-malononitriles

The synthesis of cyanoformamides via a CsF-promoted decyanation/oxidation cascade of N,N-disubstituted aminomalononitriles.

Cubanes in Medicinal Chemistry

Cubane is a highly strained saturated hydrocarbon system that has historically been of interest in theoretical organic chemistry. More recently it has become a molecule of interest for biological applications due to its inherent stability and limited toxicity. Of greater significance is the ability to potentially functionalize cubane at each of its carbon atoms, providing complex biologically active molecules with unique spatial arrangements for probing active sites. These characteristics have led to an increased use of cubane in pharmaceutically relevant molecules. In this Perspective we describe synthetic methodology for accessing a range of functionalized cubanes and their applications in pharmaceuticals. We also provide some perspectives on challenges and future directions in the advancement of this field.