ALKYLATION STUDIES WITH ISOPROPYLIDENE MALONATE UNDER PTC AND DIBENZO-(18)-CROWN-6

Isopropylidene malonate (2,2-dimethyl-4,6-dioxo-1,3-dioxane, Meldrum's acid) has a high acidity(pK(1) = 4.97), a rigid cyclic structure and can undergo easy hydrolysis. It has become an attractive reagent in or ganic synthesis.(1) For (2-5) example, it can readily undergo Knoevena gel condcensation, (2-5) Michael addition,(6-7) and acylation(8,9) rea ctions. However, few reports on its alkylation are reported.(10-13) On alkylation of isopropylidene malonate under (20% aqueous sodium hydro xide (TEBA) the ring underwent cleavage and the main product was alpha ,alpha-dimethylmalonic acid methyl ester. This problem was solved by t he use of solid potassium carbonate in place of 20% aqueous sodium hyd roxide to avoid hydrolysis and let the reaction undergo under solid-li quid phase-transfer conditions.(14) However, these require reflux cond itions and prolonged reaction times (4 to 8 h.). Our results on the us e of combination of a phase-transfer catalyst and crown ether promoted us to investigate the bis alkylation studies with isopropylidene malo nate.