Structure of Organic Compound (E)-3-((S)1-Phenylethylamine)methylene R (+) Camphor
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TRUCTURE OF ORGANIC COMPOUNDS
Structure of Organic Compound (E)-3-((S)1-Phenylethylamine)methylene R (+) Camphor A. Mirandaa,*, P. Arroyob, M. Zarragab,*, S. A. Suarezc, R. Baggiod, and Y. Morenoe,* a
Departamento de Química, Facultad de Ciencias Naturales, Universidad Metropolitana de Ciencias de la Educación, Ciencias, Chile b Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad de Concepción, Edmundo Larenas 234, Concepción, Chile c INQUIMAE, CONICET and Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, Núñez (C1428EHA), CABA, Argentina d Gerencia de Investigación y Aplicaciones, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Buenos Aires, Argentina e Facultad de Ciencias Básicas, Universidad Santo Tomás, Limonares 190, Viña del Mar, Chile *e-mail: [email protected] Received December 27, 2019; revised April 26, 2020; accepted May 7, 2020
Abstract—The synthesis and crystal structure of (E)-3-((S)-1-phenylethylamine)methylene R-(+) camphor are discussed. The 1H NMR spectrum in a chloroform solution indicates the existence of a mixture of two tautomers, the main tautomer corresponds to the E-isomer. On the other hand, in the solid state, the crystal structure solved by X-ray diffraction shows only the occurrence of this latter form. Crystal data: monoclinic (P21), a = 11.019(4) Å, b = 6.782(2) Å, c = 11.186(4) Å, β = 101.843(4)°. DOI: 10.1134/S1063774520070111
INTRODUCTION Camphor is a compound that occurs in nature in both chiral forms (dextro–levo), so it is widely used as inductor of chirality in various asymmetric reactions [1]. In this regard, the nitrogen derivatives of R (+) camphor have shown great versatility in organic synthesis, forming chiral metal complexes successfully used in the synthesis of chiral alcohols [2]. That’s why it is of great interest to know the structures of this ligand in the solid state in order to analyze its ability to form complexes. One of the most characteristic derivatives of nitrogen camphor are Schiff bases, obtained from 3-formyl camphor and primary amines formed upon dissolution of a mixture of tautomers, the predominant isomer of which in dissolution is strongly dependent on steric factors for the nitrogen atom [3]. We present here the synthesis of one such compound, the E isomer of 3-((S)-1-phenylethylamine) methylene (R) (+) camphor, and its structural analysis using 1H NMR spectroscopy and X-ray diffraction. The latter technique has been complemented by a theoretical evaluation of non-covalent interactions strength via an AIM approach [4, 5].
EXPERIMENTAL Synthesis and 1H NMR Spectroscopy All isomeric reagents and solvents employed were commercially available and used as they were, without further purification (Merck reagents). 3-(1-Phenylmethylamine)methylene camphor is a condensation product of formyl camphor and S-1-phenylethylamine, which is obtained by refluxing the amine (1.21 g, 0.01 mol) with f
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