Dynamic NMR and X-ray diffraction study of (N-B)-diphenyl(2-aminoethoxy) borane derivatives of ephedrines and pseudoephedrines
Por:
Höpfl H., Farfán N., Castillo D., Santillan R., Contreras R., Martínez-Martínez F.J., Galván M., Alvarez R., Fernández L., Halut S., Daran J.-C.
Publicada:
1 ene 1997
Resumen:
The preparation and characterization of various (N-B)-diphenyl-(2-aminoethoxy)boranes derived from ephedrine and pseudoephedrine derivatives (1b-6b) are reported: (N-B)-diphenyl(1-(R)-phenyl-2-(S)-methyl-2-aminoethoxy)borane (1b), (N-B)-diphenyl(1-(R)-phenyl-2-(R)-methyl-2-aminoethoxy)borane (2b), (N-B)-diphenyl[N-(R)-methyl-(1-(R)-phenyl-2-(S)-methyl-2-aminoethoxy)]borane (3b-trans), (N-B)-diphenyl[N-(S)-methyl-(1-(R)-phenyl-2-(S)-methyl-2-aminoethoxy)]borane (3b-cis) (N-B)-diphenyl[N-(S)-methyl-(1-(R)-phenyl-2-(R)-methyl-2-aminoethoxy)]borane (4b-trans) (N-B)-diphenyl[N,N-dimethyl-(1-(R)-phenyl-2-(S)-methyl-2-aminoethoxy)]borane (5b) and (N-B)-diphenyl[N,N-dimethyl-(1-(R)-phenyl-2-(R)-methyl-2-aminoethoxy)]borane (6b). The five membered N ? B cyclic structures 1b-6b were assigned based on 1H-, 13C-, 11B- and 15N-NMR data and all compounds except for 3b-trans were subjected to X-ray diffraction analysis showing N ? B bond lengths of 1.66(2) and 1.64(2) Å for 1b, 1.657(9) and 1.664(9) Å for 2b, 1.68(2) Å for 3b-cis, 1.66(1) Å for 4b-trans, 1.744(8) Å for 5b and 1.74(1) Å for 6b. The study of the intramolecular N ? B coordination by means of dynamic NMR spectroscopy afforded AG* values of 67.9, 70.9, 64.8, 68,2, 49.7 and 52.7kJmol~' for the dissociation of the N ? B bond in compounds 1b-6b respectively. The results show that steric interactions between the substituents at the (2-aminoethoxy)borane ring determine the stability of the N ? B bond as well as the nitrogen configuration. Theoretical calculations of the electrostatic charges for the boron and nitrogen atoms in 1b, 2b, 3b-cis, 3b-trans, 4b-cis, 5b and 6b show that the increase of positive charge on the nitrogen atom causes a shift to lower frequencies in the I5N NMR spectra. © 1997 Elsevier Science S.A.
Filiaciones:
Höpfl H.:
Departamento de Química, Ctro. de Invest. y de Estud. A., Apdo. Postal 14-740, 07000 México, D.F., Mexico
Farfán N.:
Departamento de Química, Ctro. de Invest. y de Estud. A., Apdo. Postal 14-740, 07000 México, D.F., Mexico
Castillo D.:
Departamento de Química, Ctro. de Invest. y de Estud. A., Apdo. Postal 14-740, 07000 México, D.F., Mexico
Santillan R.:
Departamento de Química, Ctro. de Invest. y de Estud. A., Apdo. Postal 14-740, 07000 México, D.F., Mexico
Contreras R.:
Departamento de Química, Ctro. de Invest. y de Estud. A., Apdo. Postal 14-740, 07000 México, D.F., Mexico
Martínez-Martínez F.J.:
Departamento de Química, U. Profesional I., Av. Acueducto s / n, 07340 México, D.F., Mexico
Galván M.:
Depto. Química, Unidad Iztapalapa, Univ. Autónoma Metropolitana, Apdo. Postal 55-534, 09340 México, D.F., Mexico
Alvarez R.:
Depto. Química, Unidad Iztapalapa, Univ. Autónoma Metropolitana, Apdo. Postal 55-534, 09340 México, D.F., Mexico
Fernández L.:
Unidad Azcapotzalco, Av. San Pablo No. 180, México, D.F., Mexico
Halut S.:
Lab. de Chim. des Metaux de T., Universite Pierre et Marie Curie, 4, Place Jussieu, Boite No. 42, 75252 Paris, Cedex 05, France
Daran J.-C.:
Lab. de Chim. des Metaux de T., Universite Pierre et Marie Curie, 4, Place Jussieu, Boite No. 42, 75252 Paris, Cedex 05, France
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