Puzzling Reaction of Imidazole with Methyl Parathion: P=S versus P=O Mechanistic Shift Dilemma in Organophosphates.

Abstract

Organophosphates (OPs) constitute many toxic agrochemicals and warfare and can undergo a wide spectrum of mechanisms, some which are fairly unexplored. In this sense, concise mechanistic elucidation stands out as a strategic tool for achieving efficient detoxification and for monitoring processes. Particularly intriguing is the effect of substituting the oxygen atom of the phosphoryl moiety (P=O) in OPs with a sulfur atom to give the thio-derived OPs (i.e., OTPs, P=S). In general, imidazole (IMZ) reacts very efficiently with OPs by targeting the phosphorus atom, although herein we evidence a thio-driven shift with OTPs: IMZ undergoes unusual nucleophilic attack at the aliphatic carbon atom of methyl parathion. Alkylation of IMZ under mild conditions (aqueous weakly basic medium) is also novel and should be applicable to other novel IMZ-based architectures, and thereby, it can be a great ally for organic synthesis. Overall, a broader understanding of the mechanistic trend involved in such highly toxic agents is provided.