Phase-Transfer Catalysis: Phosphorylation of β-Dicarbonyl Compounds

Abstract

Although we have found that diethyl phosphorochloridate and diethyl phosphorochloridothionate react exothermically with hydroxide ions under phase-transfer conditions to yield the corresponding pyrophosphates (I-II), we now report that the phase-transfer catalysed phosphorylation of pentan-2, 4-dione and of ethyl acetoacetate produces the enol phosphates (III and IV). The yields are generally better than those obtained using the sodium or copper salts and, in contrast with the heterogeneous reactions, the E-enol phosphates are the predominant products of the phase-transfer catalysed reactions (Table 1). In the case of the phosphorylation of ethyl acetoacetate, the E-enol phosphate is formed to the complete exclusion of the Z-isomer. These observations parallel those reported for the phase-transfer catalysed acetylation and benzoylation of β-dicarbonyl compounds.³