Understanding Synthesis Parameters for Thionation of Phosphonates Associated with the Chemical Weapons Convention through Principal Component Analysis

Abstract

Thiophosphonates, a class of the organophosphate compounds, are of pharmaceutical and agricultural significance. Albeit their broad scope for peaceful uses, they may also be precursors and markers to toxic chemicals, such as the nerve agent VX and other V-series agents, leading to their inclusion into the Annex on Chemicals of the Chemical Weapons Convention (CWC). Considering that they are related to chemical warfare agents and the position of our laboratory as an Organization for the Prohibition of Chemical Weapons (OPCW) Designated Laboratory for analysis of authentic environmental samples, this study aims to contribute to the understanding of the synthesis of thiophosphonates through O,O’-diethyl methylphosphonate conversion to O,O’-diethyl methylphosphonothioate using Lawesson’s reagent, exploring different conditions previously reported by the literature, in order to further build a compound library for CWC verification purposes. Synthesis of the compounds has been carried out in sealed, pressure tubes, adding novelty to the present study. Reactions were followed by gas chromatography and 31P nuclear magnetic resonance, and principal component analysis was employed to understand the intricate factors influencing thiophosphonate synthesis yield as duration, temperature and solvent. The research aims to reinforce or challenge existing scientific knowledge, providing insights into parameters related to phosphonate thionation using Lawesson’s reagent, contributing to a deeper understanding of this chemical reaction.