Direct Aryloxylation/Alkyloxylation of Dialkyl Phosphonates for the Synthesis of Mixed Phosphonates

Coupling of 1-Chloro-N,N-diisopropylphosphanamine-Based Reagents with Alcohols and Thiosulfonates: A Precise Construction of O-P(O)-S Bonds

Herein, we present the first mild, one-step direct synthesis of mixed phosphorothioates through selective generation of O-P(O)-S bonds at rt under additive-free condition. Further, reactions of different model natural products with 1,1-dichloro-N,N-diisopropylphosphanamine helped to present an alternative dimerization strategy. The synthetic utility of the methodology was extended for the synthesis of mixed phosphoroselenoates as well. The potential of the reaction was further demonstrated for the synthesis of mixed phosphorothioate bearing two different alcohols.

Selective Esterification of Phosphonic Acids

Here, we report straightforward and selective synthetic procedures for mono- and diesterification of phosphonic acids. A series of alkoxy group donors were studied and triethyl orthoacetate was found to be the best reagent as well as a solvent for the performed transformations. An important temperature effect on the reaction course was discovered. Depending on the reaction temperature, mono- or diethyl esters of phosphonic acid were obtained exclusively with decent yields. The substrate scope of the proposed methodology was verified on aromatic as well as aliphatic phosphonic acids. The designed method can be successfully applied for small- and large-scale experiments without significant loss of selectivity or reaction yield. Several devoted experiments were performed to give insight into the reaction mechanism. At 30 °C, monoesters are formed via an intermediate (1,1-diethoxyethyl ester of phosphonic acid). At higher temperatures, similar intermediate forms give diesters or stable and detectable pyrophosphonates which were also consumed to give diesters. ³¹P NMR spectroscopy was used to assign the structure of pyrophosphonate as well as to monitor the reaction course. No need for additional reagents and good accessibility and straightforward purification are the important aspects of the developed protocols.

Fluorophosphonates on-Demand: A General and Simplified Approach toward Fluorophosphonate Synthesis

Herein, we report a general and simplified synthesis of fluorophosphonates directly from p-nitrophenylphosphonates. This FP on-demand reaction is mediated by a commercially available polymer-supported fluoride reagent that produces a variety (25 examples) of fluorophosphonates in high yields while only requiring reagent filtration for pure fluorophosphonate isolation. This reaction protocol facilitates the rapid profiling of serine hydrolases with diverse and novel sets of activated phosphonates with differential proteome reactivity. Moreover, slight modification of the procedure into a reaction-to-assay format has enabled additional screening efficiency.

Selective hydrolysis of phosphorus(V) compounds to form organophosphorus monoacids

An azide and transition metal-free method for the synthesis of elusive phosphonic, phosphinic, and phosphoric monoacids has been developed. Inert pentavalent P(v)-compounds (phosphonate, phosphinate, and phosphate) are activated by triflate anhydride (Tf2O)/pyridine system to form a highly reactive phosphoryl pyridinium intermediate that undergoes nucleophilic substitution with H2O to selectively deprotect one alkoxy group and form organophosphorus monoacids.

Stability and Efficiency of Mixed Aryl Phosphonate Prodrugs

A set of phosphonate prodrugs of a butyrophilin ligand was synthesized and evaluated for plasma stability and cellular activity. The mixed aryl acyloxy esters were prepared either via a standard sequence through the phosphonic acid chloride, or through the more recently reported, and more facile, triflate activation. In the best of cases, this class of prodrugs shows cellular potency similar to that of bis-acyloxyalkyl phosphonate prodrugs and plasma stability similar to that of aryl phosphonamidates. For example, {[((3E)-5-hydroxy-4-methylpent-3-en-1-yl) (naphthalen-2-yloxy)phosphoryl]oxy}methyl 2,2-dimethylpropanoate can activate BTN3A1 in K562 cells after just 15 minutes of exposure (at an EC₅₀ value of 31 nm) and is only partially metabolized (60 % remaining) after 20 hours in human plasma. Other related novel analogues showed similar potency/stability profiles. Therefore, mixed aryl acyloxyalkyl phosphonate prodrugs are an exciting new strategy for the delivery of phosphonate-containing drugs.

Acetonitrile Activation: An Effective Two-Carbon Unit for Cyclization

A novel activation of acetonitrile for the construction of cyclobutenones by [2+2] cyclization was developed. Acetonitrile is utilized for the first time as two-carbon (C2) cyclization building block. The present protocol successfully inhibits the competitive cycloaddition with the C≡N bond of acetonitrile, but enables the in situ formation of an unsaturated carbon-carbon bond and the subsequent cycloaddition as a C2 unit. This chemistry features simple reaction conditions, high chemoselectivities, wide substrate scope, and offers a new and practical approach to cyclobutenones and cyclobuteneimines.

Metal- and chloride reagent-free synthesis of mixed thiophosphates

Systematic synthesis of mixed thiophosphates from thiophosphates was developed.

Chemoselective Activation of Diethyl Phosphonates: Modular Synthesis of Biologically Relevant Phosphonylated Scaffolds

Phosphonates have garnered considerable attention for years owing to both their singular biological properties and their synthetic potential. State-of-the-art methods for the preparation of mixed phosphonates, phosphonamidates, phosphonothioates, and phosphinates rely on harsh and poorly selective reaction conditions. We report herein a mild method for the modular preparation of phosphonylated derivatives, several of which exhibit interesting biological activities, that is based on chemoselective activation with triflic anhydride. This procedure enables flexible and even iterative substitution with a broad range of O, S, N, and C nucleophiles.