On the structure of 3‐acetylamino‐5‐methyl‐1,2,4‐oxadiazole and on the fully degenerate rearrangements (FDR) of its anion: a stimulating comparison between the results of ‘in‐silicon chemistry’ and ‘laboratory chemistry’ |
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Authors: | Angelo Mugnoli Giampaolo Barone Silvestre Buscemi Camilla Zaira Lanza Andrea Pace Marcella Pani Domenico Spinelli |
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Institution: | 1. Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, 16146 Genova, Italy;2. Dipartimento di Chimica Inorganica e Analitica ‘S. Cannizzaro’, Università di Palermo, Viale delle Scienze, Parco d'Orleans 2, 90128 Palermo, Italy;3. Dipartimento di Chimica Organica ‘E. Paternò’, Università di Palermo, Viale delle Scienze, Parco d'Orleans 2, 90128 Palermo, Italy;4. Dipartimento di Chimica Organica ‘A. Mangini’, Università di Bologna, Via San Giacomo 11, 40126 Bologna, Italy |
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Abstract: | An accurate crystal structure determination has provided evidence for a planar conformation for 3‐acetylamino‐5‐methyl‐1,2,4‐oxadiazole ( 5 ), in agreement with quantum‐mechanical calculations in the gas phase. In the crystal, a series of strong intermolecular N7H7….O9 hydrogen bonds link the amido groups of different molecules, causing the formation of infinite parallel ordered chains. The effect of the DMSO solvent on the energy and charge distribution of compound 5 and on its relevant 5 ? anion, involved in a fully degenerate rearrangement (FDR), has been deepened by quantum‐mechanical DFT calculations. The calculated energy barrier for the FDR increases in going from in vacuo to DMSO, in agreement with previsions based on the Hughes and Ingold rules concerning the nucleophilic substitution of an anionic reagent (the deprotonated amido group in the side chain) on a neutral substrate (the 1,2,4‐oxadiazole ring). Copyright © 2009 John Wiley & Sons, Ltd. |
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Keywords: | azole‐to‐azole interconversion Boulton– Katritzky reactions density functional calculations rearrangements X‐ray diffraction |
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