Stereoelectronic effects and chiral recognition, II: Kinetic and thermodynamic control in the formation of chiral thioacetals and chiral thioethers

Liebigs Annales

Volumn , Issue 6, 1996, Pages 1009-1013

  Noe, Christian R ^a   Knollmüller, Max ^b   Ziebarth Schroth, Irene ^b   Letschnig, Marion ^b  

^a GOETHE UNIVERSITY   (Germany)

^b VIENNA UNIVERSITY OF TECHNOLOGY   (Austria)

Author keywords

Enantiomer selectivity; Kinetic effect; Stereoelectronic effect; Thioacetals; Thioethers

Indexed keywords

EID: 33748954429     PISSN: 09473440     EISSN: None     Source Type: Journal    
DOI: 10.1002/jlac.199619960622     Document Type: Article

References (20)

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5. Angew. Chem. Int. Ed. Engl. 1987, 26, 442.
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8. R. P. Volante, Tetrahedron Lett. 1981, 22, 3119-3122.
9. G. Ecker, C. R. Noe, W. Fleischhacker, Sci. Pharm. 1989, 57, 171. Use of a 90-MHz NMR spectrometer allowed easy detection of about 1% of the other diastereomer. In the case of 2a/ ent-2a and 2b/ent-2b the only impurity was a small amount (less than 5%) of the other enantiomer.
10. V. Bolitt, C. Mioskowski, Tetrahedron Lett. 1988, 29, 4583. This catalyst allows the reaction rate to be adjusted much more easily than the commonly used p-toluenesulfonic acid.
11. [2]. This result can now be related to an early work-up of the reaction mixture before the thermodynamic equilibrium was reached.
12. C. R. Noe, M. Knollmüller, E. Wagner, H. Völlenkle, Chem. Ber. 1985, 118, 3299-3310.
13. B, respectively] (F = face), if in the addition of a R-X-H compound (X = multivalent hetero atom) an A-type [and B-type, respectively] chirality centre is generated.
14. M. Letchnig, Diploma Thesis, TU Wien 1987.
15. K. Dungler, Doctorate Thesis, TU Wien 1988.
16. E. Jangg, Doctorate Thesis, TU Wien 1990.
17. The importance of ground and transition state π-π interactions is well established, see for example: C. R. Noe, C. Miculka, H. Völlenkle, Monatsh. Chem. 1994, 125, 983-990;
18. B. Mezrhab, F. Dumas, J. d'Angelo, C. Riche, J. Org. Chem. 1994, 59, 500-503.
19. 2 is situated antiperiplanar to 2 σ* orbitals of pl-C bonds and therefore has an increased acidity. A prerequisite of this approach is however that in the kinetic case deprotonation in the transition state plays a decisive role: Similarly, it might be assumed that in the reaction mixture protonation of X required for retroreaction of diastereomers AA/AB occurs preferably at the second free X electron pair of the AB diastereomer, which is the most basic electron pair, because it is not involved into a n-σ* interaction. This would favor retroreaction of the AB diastereomer and accelerate in addition the establishment of the thermodynamic equilibrium.
20. C. R. Noe, Chem. Ber. 1982, 115, 1576-1590.