Déroulement Anormal d'une réaction de Michaelis-Becker: Caractère ambident de l'anion diéthylphosphonate (C2H5O)2PO−; stéréochimie de la réaction de Michaelis-Becker

Abstract

The reaction of sodium diethylphosphonate NaOP(OC2H5)2 with the mesylates of cis and trans-4-t-butyl cyclohexanols has been studied in toluene, dioxane, and dimethylformamide (DMF). Beside the products expected from the reaction (elimination and P-alkylation products originating from initial O-attack have been isolated. This latter reaction competes with P-alkylation (normal Michaelis–Becker reaction) and is the only substitution reaction in DMF. Results are interpreted in terms of the HSAB (Hard and Soft Acids and Bases) theory and by preferential solvation. Since the substitution products are of inverted configuration, the SN2 mechanism seems to be well substantiated.