Synthesis of Mixed Phosphonate Esters and Amino Acid-Based Phosphonamidates, and Their Screening as Herbicides

While organophosphorus chemistry is gaining attention in a variety of fields, the synthesis of the phosphorus derivatives of amino acids remains a challenging task. Previously reported methods require the deprotonation of the nucleophile, complex reagents or hydrolysis of the phosphonate ester. In this paper, we demonstrate how to avoid these issues by employing phosphonylaminium salts for the synthesis of novel mixed n-alkylphosphonate diesters or amino acid-derived n-alkylphosphonamidates. We successfully applied this methodology for the synthesis of novel N-acyl homoserine lactone analogues with varying alkyl chains and ester groups in the phosphorus moiety. Finally, we developed a rapid, quantitative and high-throughput bioassay to screen a selection of these compounds for their herbicidal activity. Together, these results will aid future research in phosphorus chemistry, agrochemistry and the synthesis of bioactive targets.

Beyond Amide Bond Formation: TCFH as a Reagent for Esterification

In this Communication, an investigation of the combination of N,N,N',N'-tetramethylchloroformamidinium hexafluorophosphate (TCFH) and N-methylimidazole (NMI) for the synthesis of esters and thioesters is described. This work revealed the unique challenges of the reactions of less nucleophilic alcohols and more reactive thiols with the N-acyl imidazolium intermediate and led to the identification of general enabling conditions that provide high yields and selectivity for a range of alcohols and thiols.

First GC/MS identification of aqueous ammonia: utilization of ethenesulfonyl fluoride as a selective and rapid derivatization reagent of ammonia in aqueous media

Identification as well as quantification of ammonia are required in some analytical fields including forensic science. For this purpose, gas chromatography/mass spectrometry (GC/MS) analysis is one of the most suitable techniques. Although ammonia needs to be derivatized for GC/MS analysis, conventional derivatization reagents require anhydrous conditions because they are highly reactive with water. Here, we investigated ethenesulfonyl fluoride (ESF) as a selective reagent for ammonia derivatization in aqueous media to develop a rapid identification method for ammonia in aqueous media. The Michael addition reaction of ammonia with ESF rapidly produced a tri-ESF derivative suitable for GC/MS analysis. We optimized the derivatization reaction conditions and extraction solvent. With the optimized protocol, the detection limit for aqueous ammonia was 0.05 μg mL-1. The calibration curve showed good linearity (R2 = 0.9998) in the range of 0.10-100.0 μg mL-1, and the accuracy (% bias) and the precision (% relative standard deviation) for concentrations of 0.10, 0.25, 10.0, and 75.0 μg mL-1 were within ± 10% (intra- and inter-day). The proposed ESF-based method could quantify ammonia in samples containing interfering nucleophilic substances. This method was successfully applied to ammonia-containing commercial products.

Catalytic Asymmetric Hydroalkoxylation of C-C Multiple Bonds

Asymmetric hydroalkoxylation of alkenes constitutes a redox-neutral and 100% atom-economical strategy toward enantioenriched oxygenated building blocks from readily available starting materials. Despite their great potential, catalytic enantioselective additions of alcohols across a C-C multiple bond are particularly underdeveloped, especially compared to other hydrofunctionalization methods such as hydroamination. However, driven by some recent innovations, e.g., asymmetric MHAT methods, asymmetric photocatalytic methods, and the development of extremely strong chiral Brønsted acids, there has been a gratifying surge of reports in this burgeoning field. The goal of this review is to survey the growing landscape of asymmetric hydroalkoxylation by highlighting exciting new advances, deconstructing mechanistic underpinnings, and drawing insight from related asymmetric hydroacyloxylation and hydration. A deep appreciation of the underlying principles informs an understanding of the various selectivity parameters and activation modes in the realm of asymmetric alkene hydrofunctionalization while simultaneously evoking the outstanding challenges to the field moving forward. Overall, we aim to lay a foundation for cross-fertilization among various catalytic fields and spur further innovation in asymmetric hydroalkoxylations of C-C multiple bonds.