a b s t r a c tThe treatment of cerium metal with ethyl bromosuccinate (1) forms the stabilized organolanthanoid intermediate (2), which reacts with carbonyl compounds in a Reformatsky-type reaction, under mild conditions, to produce functionalized c-substituted paraconic acids (4) in good yields.Ó 2012 Elsevier Ltd. All rights reserved.The synthesis of c-butyrolactones is important not only because they occur widely in nature, but also because they constitute a particularly useful class of synthons of numerous compounds possessing biological activies. 1 In this context, paraconic acids (bearing a carboxylic acid function at the position b to the carbonyl, see Scheme 1), constitute an important class of c-butyrolactones that showed antitumor and antibiotic activies. 2 Due to the important biological activities of paraconic acids, several methods have been described for the synthesis of natural products containing b-carboxylated c-butyrolactones, including a variation of the Perkin-Fittig condensation, 3 multicomponent reactions, 4 ring-closing metathesis of two electron deficient olefins, 5 free-radical-mediated conjugate additions, 6 and aldol reactions of dioxanes. 7The Reformatsky reaction in its original form uses a-halo esters as substrates to form the stabilized zinc enolates which will be added to carbonyl compounds generating b-hydroxy esters. This is a well-known synthetic methodology, with widespread use in a number of multistep syntheses. 8 Many other metals have been used in Reformatsky-type reactions, such as cerium, 9-11 magnesium, 12 nickel, 13 lithium, 14 and mischmetal 15 to allow the use of milder reaction conditions or obtaining better yields.More recently, however, Fukuzawa and co-workers 9 have demonstrated that b-halo esters can also be used in a kind of homoReformatsky reaction, because the anion in the b-position can also be stabilized, particularly if zinc is replaced by certain metals such as cerium or samarium. In these cases, due to the relative position of the groups, c-lactones are obtained instead of hydroxy-esters.We have thus decided to study the synthesis of paraconic acids through a Reformatsky-type reaction of ethyl bromosuccinate with carbonyl compounds mediated by cerium, which could stabilize the anion both as an enolate and as a complex with the b-carbonyl ester group (Scheme 1).The reaction as depicted in Scheme 2 was performed with ethyl bromosuccinate, cerium metal, and several different carbonyl substrates. Diols 5 form as by-products probably through free radical dimerization 8,16 of the carbonyl substrates. The results are summarized in Table 1. 17 0040-4039/$ -see front matter Ó