Alkylation at the one available acidic hydrogen, followed by removal of the allyl group with the reagent (2-propene)Ti(O-i-Pr)2, readily prepared from Ti(O-i-Pr)4 and i-PrMgCl, gives the mono-alkyl malonate. Diethyl allylmalonate can thus be regarded as a mono-protected form of diethyl malonate: J. Org. Chem., 61, 2266 (1996):