Alkylation reactions of ethyl malonate, ethyl acetoacetate, and acetylacetone by gas–liquid phase-transfer catalysis (G.L.–P.T.C.)
Malonyl, acetoacetyl, and acetylacetonyl alkylation reactions have been carried out in the gaseous state under gas–liquid phase-transfer catalysis (g.l.–p.t.c.) conditions using potassium carbonate or sodium hydrogen carbonate as the base. No alkali metal was used to generate the reactive anion. No solvents are used in the process, and the reaction mixture requires no stirring. The phase-transfer catalysts which promote the reaction: phosphonium salts, crown ethers, and poly(ethylene glycol) are also the medium in which the reaction occurs; they direct C- or O-alkylation, as a function of the methylene compound and the alkylating agent used. The malonic ester alkylation using poly(ethylene glycol) gives rise to improved selectivity for C-monoalkylation compared with the other catalysts.