0022-4766/10/5102-0251 © 2010 Springer Science+Business Media, Inc. 251 Journal of Structural Chemistry. Vol. 51, No. 2, pp. 251-257, 2010 Original Russian Text Copyright © 2010 by T. M. Barhoumi-Slimi, M. T. Ben Dhia, M. Nsangou, M. M. El Gaied, and M. R. Khaddar CHARACTERIZATION AND STEREOCHEMISTRY OF ALKYL 2-CHLORO-3-FORMYLACRYLATES: EXPERIMENTAL NMR AND THEORETICAL DFT STUDIES T. M. Barhoumi-Slimi, 1 M. T. Ben Dhia, 1 M. Nsangou, 2 M. M. El Gaied, 1 and M. R. Khaddar 1 UDC 547-32;544.122;544.176;539.19 The synthesis of alkyl 2-chloro-3-formylacrylates 1 from alkyl pyruvates was carried out using Vilsmeier reaction. The reaction is highly stereoselective and leads to a 95:5 mixture of Z and E stereoisomers. Both stereoisomers were characterized by 1 H and 13 C NMR. In CDCl 3 solution, the NMR data, particularly the NOEDIFF experiments, show that the major species formed is the Z stereoisomer. Heating compound 1 in THF at reflux afforded the cyclic product 2 in 90 % yield. The interpretation of the experimental data were further supported by DFT/B3LYP calculations. Keywords: synthesis, Vilsmeier reaction, stereoisomerism, stereoselectivity, cyclization, NMR, NOEDIFF, B3LYP. INTRODUCTION ,-Unsaturated carbonyl systems form part of the most interesting synthons in organic synthesis [1]. When other functions are present together with these systems, a large variety of supplementary reactions may take place leading to interesting molecules. For instance, the ethyl 3-formylprop-2-enoate is a useful precursor for the synthesis of natural products such as fruity flavours [2] used in food industry, natural insecticides [3] and hypoglycins [4]. The Vilsmeier reaction is widely used for the synthesis of many heterocyclic compounds [5, 6], particularly for the synthesis of substituted -chloroacrylaldehydes [6-8] which are much less reported in the literature. Surprisingly, very few authors have reported the synthesis of the chlorinated derivative of ethyl 3-formylbut-2-enoate, the alkyl 2-chloro-3- formylacrylate 1 [9] which could be used as a precursor for the synthesis of heterocyclic molecules and biomolecules. Fariña et al. [9a] have reported the synthesis of methyl 2-chloro-3-formylacrylate starting from pseudoesters in several steps. In this paper, we describe the synthesis of compound 1 through a one-pot Vilsmeier reaction on alkyl pyruvates and investigate its stereochemistry using both experimental NMR technique and theoretical DFT calculations. 1 Laboratory of Structural Organic Chemistry: Organic Synthesis, Faculty of Sciences of Tunis, 1060 Tunis, Tunisia; b.sthouraya@yahoo.com. 2 Department of Physics, Faculty of Science, University of Ngaoundere, Cameroon. The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 51, No. 2, pp. 266-271, March-April, 2010. Original article submitted April 14, 2008.