Asymmetric hetero-Diels-Alder reactions. Mechanism of the reaction of alkenyloxazolines with isocyanates

Tetrahedron Letters

Volumn 39, Issue 48, 1998, Pages 8911-8914

  Elliott, Mark C ^a   Kruiswijk, Elbertus ^a   Willock, David J ^a  

^a CARDIFF UNIVERSITY   (United Kingdom)

Author keywords

Asymmetric synthesis; Diels Alder reactions

Indexed keywords

ALKENYL GROUP; ISOCYANIC ACID DERIVATIVE; OXAZOLINE DERIVATIVE; PYRIMIDINE DERIVATIVE;

ARTICLE; CHEMICAL BOND; CHEMICAL REACTION; DECOMPOSITION; DIASTEREOISOMER; HEATING; ISOMERISM; NUCLEAR MAGNETIC RESONANCE; STEREOCHEMISTRY; STRUCTURE ANALYSIS; SYNTHESIS; THERMODYNAMICS;

BETULACEAE;

EID: 0032569815     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)01949-2     Document Type: Article

References (8)

1. 1. M. C. Elliott and E. Kruiswijk, Chem. Commun. 1997, 2311; M. C. Elliott, D. E. Hibbs, D. S. Hughes, M. B. Hursthouse, E. Kruiswijk and K. M. A. Malik, J. Chem. Crystallogr. 1998, in press.
2. 1. M. C. Elliott and E. Kruiswijk, Chem. Commun. 1997, 2311; M. C. Elliott, D. E. Hibbs, D. S. Hughes, M. B. Hursthouse, E. Kruiswijk and K. M. A. Malik, J. Chem. Crystallogr. 1998, in press.
3. 2. For a review of the hetero-Diels-Alder reaction see: L. Tietze and G. Kettschau, Top. Curr. Chem., 1997, 189, 1.
4. 3. W. M. F. Fabian and G. Kollenz, J. Phys. Org. Chem., 1994, 7, 1.
5. +, 21%), 362 (100), 285 (34) and 166 (73).
6. 5. There is a balance between isomerisation and decomposition. The isomerisations must be carried out above the melting point of the pure 3R,7R isomer (3a, 150°C; 3b, 220°C; 3c, 140°C; 3d, 64°C; 3e, 68°C), although if this is above 150°C decomposition predominates and only a trace of the 3R,7S isomer can be detected (with the exception of 4b which can be prepared directly from the alkenyloxazoline at 150°C despite 3b having a melting point of 220°C).
7. 6. Simple energy minimisations were performed using the semi-empirical package (PM3) in MacSpartan Plus 1.1.7 (Wavefunction Inc.). For each isomer the minimisation was repeated starting at each gauche conformation of the ethyl group in order to be confident that the global minimum had been found.
8. 7. Transition state calculations performed on a Silicon Graphics multiprocessor Origin 2000.