Palladium-Catalyzed Phosphonylation: Synthesis of C3-, C4-, and C5-Phosphonylated Pyrazoles

Comprehensive Biosafety Profile of Carbomer-Based Hydrogel Formulations Incorporating Phosphorus Derivatives

Determining the safety of a newly developed experimental product is a crucial condition for its medical use, especially for clinical trials. In this regard, four hydrogel-type formulations were manufactured, all of which were based on carbomer (Blank-CP940) and encapsulated with caffeine (CAF-CP940), phosphorus derivatives (phenyl phosphinic (CAF-S1-CP940) and 2-carboxyethyl phenyl phosphinic acids (CAF-S2-CP940)). The main aim of this research was to provide a comprehensive outline of the biosafety profile of the above-mentioned hydrogels. The complex in vitro screening (cell viability, cytotoxicity, morphological changes in response to exposure, and changes in nuclei morphology) on two types of healthy skin cell lines (HaCaT-human keratinocytes and JB6 Cl 41-5a-murine epidermal cells) exhibited a good biosafety profile when both cell lines were treated for 24 h with 150 μg/mL of each hydrogel. A comprehensive analysis of the hydrogel's impact on the genetic profile of HaCaT cells sustains the in vitro experiments. The biosafety profile was completed with the in vivo and in ovo assays. The outcome revealed that the developed hydrogels exerted good biocompatibility after topical application on BALB/c nude mice's skin. It also revealed a lack of toxicity after exposure to the hen's chicken embryo. Further investigations are needed, regarding the in vitro and in vivo therapeutic efficacy and safety for long-term use and potential clinical translatability.

Facile Synthesis of H-Phosphinates from P(OR)3 or ClP(OR)2 via SiO2-Promoted Hydrolysis

H-Phosphinates represent a valuable class of organophosphorus building blocks and catalytic ligands. The existing synthetic approaches are generally associated with the use of strong acids, the need for meticulous treatment of intermediates, and the limitation of only P-aryl introductions. Following a comprehensive investigation into the unexpected SiO2-promoted hydrolysis observed during the chromatography workup of the crude R'P(OR)2 intermediates, we have developed an extremely simple and general synthetic route to H-phosphinates from commercially available Grignard reagents and P(OR)3. An alternative approach involved the use of ClP(OR)2 in place of P(OR)3, which proved to be a valuable strategy for the preparation of sterically hindered ArMgBr substrates bearing bulky ortho-substituted motifs. A library of 36 structurally diverse P-(cyclo)alkyl and P-(hetero)aryl H-phosphinates was thus obtained in moderate to high yields using this practical protocol. Furthermore, the CuCl2-mediated P(O)-H bond derivations were also examined, resulting in the formation of the corresponding EtOPhP(O)-X (X = O, N, S) compounds in nearly quantitative yields.

Kinetically Controlled Stereoselective Synthesis of 2-Oxo-2-aryl-1,3,2-dioxaphosphorinane Derivatives via a Palladium-Catalyzed Reaction

Chiral phosphonate esters have been widely applied in the fields of organic chemistry, medicine, and photoelectric materials. However, it requires the challenging enantioselective synthesis of cyclic phosphonate esters with the desired chiral configuration. The two epimers of 2-oxo-2H-1,3,2-dioxaphosphorinane derivatives should have different reactivities in Pd-catalyzed coupling reactions, which could lead to an effective methodology for the asymmetric synthesis of 2-oxo-2-aryl-1,3,2-dioxaphosphorinane derivatives. A thorough investigation of the coupling reactions both computationally and experimentally led to the stereoselective synthesis of chiral cyclic phosphonate esters. The axial isomer of products can be obtained with both high diastereoselectivity and good chemical yields from the mixture of 2-oxo-2H-1,3,2-dioxaphosphorinane derivatives under kinetically controlled conditions.

Diversity-Oriented Synthesis toward Aryl- and Phosphoryl-Functionalized Imidazo[1,2-a]pyridines

We report herein an efficient synthesis of diversely polysubstituted imidazo[1,2-a]pyridines, a family of aza-heterocycles endowed with numerous biological properties, through a sequence involving two consecutive palladium-catalyzed cross-coupling reactions. First, we demonstrated that a Hirao coupling occurred straightforwardly in high yields at positions 3, 5, and 6 of imidazopyridine derivatives, giving access to a wide variety of substituted phosphonates, phosphinates, and phosphine oxides. In a second step, direct CH-arylation of phosphorylimidazopyridines with aryl halides was found to be effective and fully selective, leading to 3-aryl-substituted imidazopyridines in moderate to high yields depending on steric hindrance.