Effect of the nature of solid metal fluorides on the alkylation kinetics of CH-acids in the presence of onium salts

The selective C-alkylation of ethyl 2-methylacetoacetate by prenyl chloride in the presence of solid metal fluorides proceeds at room temperature with yields of from 2.5 to 87.5% depending on the nature of the deprotonating agent. The alkylation rate increases in going from LiF to CsF. A linear correlation was found between the activation free energy for the alkylation reaction and the crystal lattice energy of the solid metal fluorides. Ion exchange was not observed between tetrabutylammonium chloride and solid KF, CsF, and CaF₂ in acetonitrile. The extent of the exchange with KF·2H₂O over 10 h did not exceed 6%. Deprotonation of ethyl 2-methylacetoacetate by the action of the solid metal fluorides was not observed. Loss of the CH-acid is found in the presence of an onium salt, which varies upon, changing the nature of the deprotonating agent: LiF-NaF=KF (30%), RbF (54%), CsF (90%), CaF₂ (35%).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2690–2696, December, 1989.