SciELO - Scientific Electronic Library Online

 
vol.53 número3Towards the Stepwise Assembly of Molecular Borromean Rings: A Donor-Acceptor Ring-in-Ring ComplexOn the Origin of the Conformationally Non-Interconvertable Isomers of Bisphenyldirhodium(III) Caprolactamate índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Journal of the Mexican Chemical Society

versión impresa ISSN 1870-249X

J. Mex. Chem. Soc vol.53 no.3 México jul./sep. 2009

 

Article

 

Allylic Proton–Proton Coupling in Stereodefined Alkylidenecyclobutanes and Alkylidenecycopentanes*

 

William F. Bailey1* and Timo V. Ovaska2*

 

1 Department of Chemistry, The University of Connecticut, Storrs, Connecticut 06269–3060, USA.*Responsible author: William.Bailey@uconn.edu

2 Department of Chemistry, Connecticut College, New London, Connecticut 06320–4196, USA.*Responsible author: tvova@conncoll.edu

 

Received June 28, 2009
Accepted August 14, 2009

 

Abstract

Analysis of the 1H NMR spectra of eight stereodefined alkylidenecycloalkanes allows determination of the magnitude of allylic coupling in these compounds. In contrast to the trend normally observed, the magnitude of transoid–allylic coupling was found to be invariably greater by ~0.5 Hz than the cisoid–allylic coupling. The larger transoid–allylic coupling may be attributed to the slightly smaller dihedral angle relating allylic =C–C–H plane with the C=C–C plane in the E–isomers.

Keywords: Proton NMR, Allylic Coupling, Alkylidenecycloalkanes.

 

Resumen

El análisis de los espectros de RMN protónica de ocho alquilidéncicloalcanos estereoisoméricos permite determinar la magnitud de los acoplamientos alílicos en estos compuestos. En contraste con la tendencia normal, la magnitud de los acoplamientos en segmentos alílicos transoides es siempre mayor que la encontrada en sistemas alílicos cisoides, por aproximadamente 0.5 Hz. Los valores mas grandes en las constantes de acoplamiento para los sistemas transoides pudiera explicarse con base en el ángulo diedro existente entre el plano alílico =C–C–H y el plano en el segmento C=C–C presente en los isómeros E, que es ligeramente mas pequeño.

Keywords: RMN de protones, acoplamientos alílicos, alquilidéncicloalcanos.

 

DESCARGAR ARTÍCULO EN FORMATO PDF

 

Acknowledgment

This work was supported by the Connecticut Department of Economic Development. We thank the editorial board of this journal, and particularly Prof. Eusebio Juaristi, for arranging this memorial issue dedicated to Ernest Eliel.

 

References

1. (a) Bailey, W. F.; Ovaska, T. V.; Leipert, T. K. Tetrahedron Lett. 1989, 30, 3901.         [ Links ] (b) Bailey, W. F.; Ovaska, T. V. Tetrahedron Lett. 1990, 31, 627.         [ Links ]

2. Bailey, W. F.; Ovaska, T. V. J. Am. Chem. Soc. 1993, 115, 3080.         [ Links ]

3. (a) Barfield, M. J. Chem. Phys. 1964, 41, 3825.         [ Links ] (b) Barfield, M. J. Am. Chem. Soc. 1971, 93, 1066.         [ Links ]

4. Karplus, M. J. Chem. Phys. 1960, 33, 1842.         [ Links ]

5. Sternhell, S. Q. Rev., Chem. Soc. 1969, 23, 236.         [ Links ]

6. McConnell, H. M. J. Mol. Spectrosc. 1957, 1, 11.         [ Links ]

7. (a) Barfield, M.; Spear, R. J.; Sternhell, S. Chem Rev. 1976, 76, 593.         [ Links ] (b) Barfield, M. Magn. Reson. Chem. 2003, 41, 344.         [ Links ]

8. Gaudemer, A. Stereochemistry, Fundamentals and Methods; Kagan, H. B., Ed.; Georg Thieme: Stuttgart, 1977; Vol. 1, p. 46 and references contained therein.         [ Links ]

9. Burkert, U.; Allinger, N. L. Molecular Mechanics; ACS Monograph 177; American Chemical Society: Washington, DC, 1982.         [ Links ]

10. Chem 3D Pro, CambridgeSoft Corporation, Cambridge, MA.         [ Links ]

Note

*Dedicated to Professor Ernest L. Eliel: a giant in the field of stereochemistry and to us a mentor and friend to whom much is owed for his generous support and encouragement.