Flexible Synthesis of Phosphoryl-Substituted Imidazolines, Tetrahydropyrimidines, and Thioamides by Sulfur-Mediated Processes

Synthesis of Phosphorus(V)-Substituted Six-Membered N-Heterocycles: Recent Progress and Challenges

Heterocycles functionalized with pentavalent phosphorus are of great importance since they include a great variety of biologically active compounds and pharmaceuticals, advanced materials, and valuable reactive intermediates for organic synthesis. Significant progress in synthesis of P(O)R2-substituted six-membered heterocycles has been made in the past decade. This review covers the synthetic strategies towards aromatic monocyclic six-membered N-heterocycles, such as pyridines, pyridazines, pyrimidines, and pyrazines bearing phosphonates and phosphine oxides, which were reported from 2012 to 2022.

Continuous-Flow Synthesis of Thioureas, Enabled by Aqueous Polysulfide Solution

We have developed the continuous-flow synthesis of thioureas in a multicomponent reaction starting from isocyanides, amidines, or amines and sulfur. The aqueous polysulfide solution enabled the application of sulfur under homogeneous and mild conditions. The crystallized products were isolated by simple filtration after the removal of the co-solvent, and the sulfur retained in the mother liquid. Presenting a wide range of thioureas synthesized by this procedure confirms the utility of the convenient continuous-flow application of sulfur.

Chromatography-Free Multicomponent Synthesis of Thioureas Enabled by Aqueous Solution of Elemental Sulfur

The development of a new three-component chromatography-free reaction of isocyanides, amines and elemental sulfur allowed us the straightforward synthesis of thioureas in water. Considering a large pool of organic and inorganic bases, we first optimized the preparation of aqueous polysulfide solution from elemental sulfur. Using polysulfide solution, we were able to omit the otherwise mandatory chromatography, and to isolate the crystalline products directly from the reaction mixture by a simple filtration, retaining the sulfur in the solution phase. A wide range of thioureas synthesized in this way confirmed the reasonable substrate and functional group tolerance of our protocol.

Poly-tetrahydropyrimidine Antibacterial Hydrogel with Injectability and Self-Healing Ability for Curing the Purulent Subcutaneous Infection

Infections caused by pathogenic microorganisms have always been the Achilles heel in the clinic. In this work, to overcome this conundrum, we proposed an injectable multifunctional hydrogel material with outstanding antibacterial properties and self-healing properties and no adverse effects on health. The cross-linked hydrogel with three-dimensional (3D) networks was quickly formed via the dynamic Schiff base between amino-modified poly-tetrahydropyrimidine (PTHP-NH2) and multiple vanillin polymer P(DMA-VA) in 30 s. This hydrogel composite presents effective defense against both Gram-positive and Gram-negative bacteria, especially for the pyogenic Staphylococcus aureus. Moreover, the hydrogel showed almost no hemolysis and cytotoxicity. In vivo investigations indicated that hydrogels effectively killed S. aureus and protected against deterioration of inflammation. Besides, bioimaging of mice demonstrated that the hydrogel could be completely metabolized within 16 h. In a nutshell, given its outstanding antibacterial property and biocompatibility, the novel hydrogel could be an ideal candidate for the subcutaneous infection application.

Sulfur-mediated synthesis of unsymmetrically substituted N-aryl oxalamides by the cascade thioamidation/cyclocondensation and hydrolysis reaction

A facile and straightforward synthesis of unsymmetrically substituted N-aryl oxalamides from 2,2'-biphenyldiamines, 2-chloroacetic acid derivatives, elemental sulfur, and water has been developed. This protocol is distinguished by efficiency in water under metal-free conditions for N-aryl oxalamides bearing a side-chain NH2-group; it can be adapted for scale-up synthesis. The scope and limitations of this transformation have been investigated.

Iodine-promoted synthesis of pyrazoles from 1,3-dicarbonyl compounds and oxamic acid thiohydrazides

A novel approach to 3,4-dicarbonyl-substituted pyrazoles from 1,3-dicarbonyl compounds and oxamic acid thiohydrazides was developed via iodine-promoted cascade imination/halogenation/cyclization/ring contraction reaction.