ZnCl2-Mediated Double Addition of Dialkylphosphite to Nitriles for the Synthesis of 1-Aminobisphosphonates

Efficient synthesis of α-amino-vinylphosphine oxides from alkyl nitriles via manganese-catalyzed phosphinoenamination

A protocol for the synthesis of α-amino-vinylphosphine oxides by phosphinoenamination reaction between alkyl nitriles and phosphine oxides was developed. The combination of Mn(OAc)2 as a Lewis acid and guanidine as a Lewis base was found to be an efficient catalytic system for this reaction. A series of alkyl nitriles and phosphine oxides are compatible with this conversion, furnishing the desired products in up to 95% yield under mild conditions. Furthermore, this method demonstrates the capability of gram-scale synthesis.

Synthesis of 6H-Chromeno[4,3-b]quinolin-7-ylphosphonates through Three Component Phosphonylation of Coumarin Carbaldehyde and Their Antimicrobial and Photophysical Properties

Organophosphorylated coumarin derivatives were synthesized by a three-component reaction of 4-chloro-3-formylcoumarin, aromatic amines, and dialkyl phosphite in the presence of ZnCl2. This process includes the formation of C(sp3)-P and C(sp2)-N bonds in one pot. The modular scope of the reaction allowed rapid access to a variety of 6H-chromeno[4,3-b]quinolin-7-ylphosphonate derivatives in good yields. Furthermore, photophysical studies of the products revealed their stimulating fluorescence properties.

Alpha-metalated N,N-dimethylbenzylamine rare-earth metal complexes and their catalytic applications

This perspective summarizes our group's extensive research in the realm of organometallic lanthanide complexes, while also placing the catalytic reactions supported by these species within the context of known lanthanide catalysis worldwide, with a specific focus on phosphorus-based catalytic reactions such as intermolecular hydrophosphination and hydrophosphinylation. α-Metalated N,N-dimethylbenzylamine ligands have been utilized to generate homoleptic lanthanide complexes, which have subsequently proven to be highly active lanthanum-based catalysts. The main goal of our research program has been to enhance the catalytic efficiency of lanthanum-based complexes, which began with initial successes in the stoichiometric synthesis of organometallic lanthanide complexes and utilization of these species in catalytic hydrophosphination reactions. Not only have these species supported traditional lanthanide catalysis, such as the hydrophosphination of heterocumulenes like carbodiimides, isocyanates, and isothiocyanates, but they have also been effective for a plethora of catalytic reactions tested thus far, including the hydrophosphinylation and hydrophosphorylation of nitriles, hydrophosphination and hydrophosphinylation of alkynes and alkenes, and the heterodehydrocoupling of silanes and amines. Each of these catalytic transformations is meritorious in its own right, offering new synthetic routes to generate organic scaffolds with enhanced functionality while concurrently minimizing both waste generation and energy consumption. Objectives: We aim for the research summary presented herein to inspire and encourage other researchers to investigate f-element based stoichiometric and catalytic reactions. Our efforts in this field began with the recognition that potassium salts of benzyldimethylamine preferred deprotonation at the α-position, rather than the ortho-position, and we wondered if this regiochemistry would be retained in the formation of lanthanide complexes. The pursuit of this simple idea led first to a series of structurally fascinating homoleptic organometallic lanthanide complexes with surprisingly good stability. Fundamental studies of the protonolysis chemistry of these complexes ultimately revealed highly versatile lanthanide-based precatalysts that have propelled a catalytic investigation spanning more than a decade. We anticipate that this summative perspective will animate the synthetic as well as biological communities to consider La(DMBA)3-based catalytic methods in the synthesis of functionalized organic scaffolds as an atom-economic, convenient, and efficient methodology. Ultimately, we envision our work making a positive impact on the advancement of novel chemical transformations and contributing to progress in various fields of science and technology.

α-Amino bisphosphonate triazoles serve as GGDPS inhibitors

Depletion of cellular levels of geranylgeranyl diphosphate by inhibition of the enzyme geranylgeranyl diphosphate synthase (GGDPS) is a potential strategy for disruption of protein transport by limiting the geranylgeranylation of the Rab proteins that regulate intracellular trafficking. As such, there is interest in the development of GGDPS inhibitors for the treatment of malignancies characterized by abnormal protein production, including multiple myeloma. Our previous work has explored the structure-function relationship of a series of isoprenoid triazole bisphosphonate-based GGDPS inhibitors, with modifications having impact on enzymatic, cellular and in vivo activities. We have synthesized a new series of α-amino bisphosphonates to understand the impact of modifying the alpha position with a moiety that is potentially linkable to other agents. Bioassays evaluating the enzymatic and cellular activities of these compounds demonstrate that incorporation of the α-amino group affords compounds with GGDPS inhibitory activity which is modulated by isoprenoid tail chain length and olefin stereochemistry. These studies provide further insight into the complexity of the structure-function relationship and will enable future efforts focused on tumor-specific drug delivery.

Synthesis of Aminobisphosphinates through a Cascade Reaction between Hypophosphorous Acid and Bis(trimethylsilyl)imidates Mediated by ZnI2

Among phosphorylated derivatives, phosphinates occupy a prominent place due to their ability to be bioisosteres of phosphates and carboxylates. These properties imply the necessity to develop efficient methodologies leading to phosphinate scaffolds. In recent years, our team has explored the nucleophilic potential of silylated phosphonite towards various electrophiles. In this paper, we propose to extend our study to other electrophiles. We describe here the implementation of a cascade reaction between (trimethylsilyl)imidates and hypophosphorous acid mediated by a Lewis acid allowing the synthesis of aminomethylenebisphosphinate derivatives. The present study focuses on methodological development including a careful NMR monitoring of the cascade reaction. The optimized conditions were successfully applied to various aliphatic and aromatic substituted (trimethylsilyl)imidates, leading to the corresponding AMBPi in moderate to good yields.

A method for the synthesis of unsymmetric bisphosphoric analogs of α-amino acids

Herein, we describe the first universal strategy for the synthesis of unsymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogs of N-protected 1-aminobisphosphonates. The proposed user-friendly procedure, based on a one-pot reaction of the α-ethoxy derivatives of phosphorus analogs of protein and non-protein α-amino acids with triphenylphosphonium tetrafluoroborate and an appropriate phosphorus nucleophile (diethyl phenylphosphonite or methyl diphenylphosphinite), provides good to very good yields of 53-91% under mild catalyst-free conditions (temperature: rt to 40 °C, time: 1 to 6 hours). The progress of the transformation, running through the corresponding phosphonium salt as a reactive intermediate, was monitored by ³¹P NMR spectroscopy, which is a convenient tool for the identification of the transient species formed here. In this paper, we present the full characteristics of the spectroscopic properties of all 13 synthesized models of structurally diverse N-protected unsymmetric bisphosphoric analogs of α-amino acids. Therefore, these results contribute to increasing the practical applicability of our recently reported synthesis protocol of symmetric models of α-aminobisphosphonates derivatives and thus justify its universality.

One-Pot Synthesis of α-Amino Bisphosphonates from Nitriles via Tf2O/HC(OR)3-Mediated Interrupted Ritter-Type Reaction

A versatile synthesis of α-amino bisphosphonates has been achieved through one-pot interrupted Ritter-type reaction under mild conditions. The reactive Ritter intermediate nitrilium is in situ generated by treatment of nitrile with readily accessible Tf₂O/HC(OR¹)₃, which is trapped by phosphite ester to deliver the desired product. This protocol is efficient, scalable, and well compatible with a broad scope of substrates. In addition, plentiful characteristic J_P-C couplings including unusual five-bond long-range ⁵J_P-C and ³J_P-C across quaternary carbon and hetero (N) atoms were observed in ¹³C NMR spectra.

One-Pot and Catalyst-Free Transformation of N-Protected 1-Amino-1-Ethoxyalkylphosphonates into Bisphosphonic Analogs of Protein and Non-Protein α-Amino Acids

Herein, we describe the development of one-pot transformation of α-ethoxy derivatives of phosphorus analogs of protein and non-protein α-amino acids into biologically important N-protected 1-aminobisphosphonates. The proposed strategy, based on the three-component reaction of 1-(N-acylamino)-1-ethoxyphosphonates with triphenylphosphonium tetrafluoroborate and triethyl phosphite, facilitates good to excellent yields under mild reaction conditions. The course of the reaction was monitored by ³¹P NMR spectroscopy, allowing the identification of probable intermediate species, thus making it possible to propose a reaction mechanism. In most cases, there is no need to use a catalyst to provide transformation efficiency, which increases its attractiveness both in economic and ecological terms. Furthermore, we demonstrate that the one-pot procedure can be successfully applied for the synthesis of structurally diverse N-protected bisphosphonic analogs of α-amino acids. As shown, the indirect formation of the corresponding phosphonium salt as a reactive intermediate during the conversion of 1-(N-acylamino)-1-ethoxyphosphonate into a 1-aminobisphosphonate derivative is a crucial component of the developed methodology.

Hydroxy- and Amino-Phosphonates and -Bisphosphonates: Synthetic Methods and Their Biological Applications

Phosphonates and bisphosphonates are stable analogs of phosphates and pyrophosphates that are characterized by one and two carbon–phosphorus bonds, respectively. Among the various phosphonates and bisphosphonates, hydroxy and amino substitutes are of interest as effective in medicinal and industrial chemistry. For example, hydroxy bisphosphonates have proven to be effective for the prevention of bone loss, especially in osteoporotic disease. On the other hand, different substitutions on the carbon atom connected to phosphorus have led to the synthesis of many different hydroxy- and amino-phosphonates and -bisphosphonates, each with its distinct physical, chemical, biological, therapeutic, and toxicological characteristics. Dialkyl or aryl esters of phosphonate and bisphosphonate compounds undergo the hydrolysis process readily and gave valuable materials with wide applications in pharmaceutical and agriculture. This review aims to demonstrate the ongoing preparation of various classes of hydroxy- and amino-phosphonates and -bisphosphonates. Furthermore, the current review summarizes and comprehensively describes articles on the biological applications of hydroxyl- and amino-phosphonates and -bisphosphonates from 2015 until today.

Nickel-Catalyzed 1,1-Dihydrophosphinylation of Nitriles with Phosphine Oxides

Treatment of phosphine oxides with nitriles usually furnishes 1,2-dihydrophosphinylation products. Herein, we developed a nickel-catalyzed 1,1-dihydrophosphinylation of nitriles with phosphine oxides to access primary amines. This reaction proceeded smoothly under very mild conditions. A series of nitriles and phosphine oxides were compatible with this conversion, and the desired products were obtained in moderate to good yields.

ZnCl2-mediated stereo- and chemoselective synthesis of vinylphosphonates

A highly chemo- and stereoselective synthesis of diethyl (E)-2-(alkylidene)-2-phosphonoacetonitriles via the Knoevenagel condensation reaction of carbonyl compounds with diethyl cyanomethylphosphonate in the presence of zinc chloride has been achieved. By the presented method, various E-isomers of arylmethylidene phosphonates rather than Horner-Wadsworth-Emmons olefination products were obtained in good to excellent yields. Their E configurations were determined by X-ray diffraction and NMR analyses. In addition, DFT calculations provided insights into the chemo- and stereoselectivity of the reaction.

Removal performance and mechanisms of toxic hexavalent chromium (Cr(VI)) with ZnCl2 enhanced acidic vinegar residue biochar

Acidic vinegar residue (VR) and toxic hexavalent chromium (Cr(VI)) are unfavorable substances due to their toxicity against the environment. In this study, modified biochar was prepared to investigate the removal mechanisms of Cr(VI). The results showed that ZnCl₂ could yield highly aromatic products with improved pore structures. The adsorption capacity of modified biochar reached the highest efficiency (236.81 mg g^-1) when the mass ratio of ZnCl₂/VR was 1, which is higher than the control (9.96 mg g^-1). In addition, Cr(VI) adsorption coexisted with physical and chemical adsorption. The mechanisms of modified biochar to Cr(VI) removal included electrostatic attraction, pore filing, reduction and surface complexation. Notably, as a fermented product, VR biochar was a nitrogen-rich product; the formation of the amino group could provide a direct solid site for Cr(VI) adsorption. Subsequently, amorphous silica could be converted into silanol to provide additional adsorption sites. This work establishes the theoretical basis for efficient Cr(VI) removal and VR reuse.

Synthesis of New Highly Functionalized 1H-Indole-2-carbonitriles via Cross-Coupling Reactions

An approach for the preparation of polysubstituted indole-2-carbonitriles through a cross-coupling reaction of compounds 1-(but-2-ynyl)-1H-indole-2-carbonitriles and 1-benzyl-3-iodo-1H-indole-2-carbonitriles is described. The reactivity of indole derivatives with iodine at position 3 was studied using cross-coupling reactions. The Sonogashira, Suzuki–Miyaura, Stille and Heck cross-couplings afforded a variety of di-, tri- and tetra-substituted indole-2-carbonitriles.

Synthesis of Aminomethylene-gem-bisphosphonates Containing an Aziridine Motif: Studies of the Reaction Scope and Insight into the Mechanism

A broad range of N-carbamoylaziridines were obtained and then treated by the diethyl phosphonate anion to afford α-methylene-gem-bisphosphonate aziridines. Study of the reaction's scope and additional experiments indicates that the transformation proceeds via a new mechanism involving the chelation of lithium ion. This last step is crucial for the reaction to occur and disfavors the aziridine ring-opening. A phosphonate-phosphate rearrangement from a α-hydroxybisphosphonate aziridine intermediate is also proposed for the first time. This reaction provides a simple and convenient method for the synthesis of a highly functionalized phosphonylated aziridine motif.