An efficient, high-yield, three-step preparation of 4-0~0 carboxyllc acids from ybutyrolactone via silylatlon and reactlon with a Gngnard reagent is presented. The preparation of 4-0~0 carboxyllc acids 1s of interest since these compounds are, among other things, important precursors to substituted y-butyrolactones via the Y-hydroxy acid.* We report, herein on the efflclent conversion of y-butyrolactone to 4-0~0 carboxyllc acids as outlined in Scheme 1. The key factors to the success of this synthetic approach are the C-silylation of the lithium enolate of y-butyrolactone3 and the reaction of the a-sllylated lactone with a Gngnard reagent.4 Clean C-silylation of the lithium enolate of y-butyrolactone 1s accomplished by quenching with dlphenylmethylchlorosllane 335 to give 2 in 94.9% isolated yield. Treatment of t with an excess of a Gngnard reagent ln ether followed by Jones oxidation of the crude material, extraction with sodium hydroxlde solution and acldlflcatlon of the aqueous layer gives the 4-0~0 acid in good yield. The results are shown in Table I. The reaction seems to be rather general although no reaction was observed with lsopropylmagneslum bromide and tert-butylmagneslum chloride gave reduction rather than addition to the carbonyl, yleldlng succinic acid as the ultimate product. We propose that the Gngnard reagent adds to the carbonyl preferentlally from the least hindered side to give cl+u-alkoxysllane, ,$ as an intermediate. Intermediate 2 is ideally arranged to lose diphenylmethylslloxide in a cis manner6 forming the dlhydrofuran,7 3, which 1s then oxidized to the keto acid, 2.