In the footsteps of pasteur: Asymmetric induction in the solid-state photochemistry of ammonium carboxylate salts

Journal of the American Chemical Society

Volumn 121, Issue 12, 1999, Pages 2919-2920

  Cheung, Eugene ^a   Netherton, Matthew R ^a   Scheffer, John R ^a   Trotter, James ^a  

^a UNIVERSITY OF BRITISH COLUMBIA   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

AMINOKETONE; AMMONIUM DERIVATIVE; CARBOXYLIC ACID DERIVATIVE;

ARTICLE; CHEMICAL REACTION; CHEMICAL STRUCTURE; CHIRALITY; ENANTIOMER; PHOTOCHEMISTRY; PHOTOLYSIS; X RAY CRYSTALLOGRAPHY;

EID: 0033620452     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja9834327     Document Type: Article

References (18)

1. Pasteur, L. C. R. Acad. Sci. 1853, 37, 162.
2. It is to be expected that the conformationally flexible carboxylic acids (amines) that possess average achirality in solution will crystallize in homochiral conformations upon salt formation with optically pure amines (carboxylic acids). This thermodynamic component of the process, shown as the first step in Figure 1. may bias the reactant toward one of two possible diastereomeric pathways in the solid state. In the present example, the bias is large, but this need not always be the case. In general, therefore, the preference for formation of one product salt (n or p) over the other is best viewed as a kinetic differentiation between diastereomeric transition states of unequal energy.
3. For previous examples of the utilization of the ionic chiral auxiliary approach to asymmetric synthesis in solid-state organic photochemistry, see: Gamlin, J. N.; Jones, R.; Leibovitch, M.; Patrick, B.; Scheffer, J. R.; Trotter, J. Acc. Chem. Res. 1996, 29, 203 and references therein.
4. Macrocycle 1, an apparently unknown compound, mp 33-34 °C, was synthesized by conventional Dieckmann condensation methodology. All new compounds described in the present paper gave spectroscopic data and elemental analyses completely in accord with their assigned structures. Details will be provided in a subsequent full paper.
5. Reviews: (a) Wagner, P.; Park, B.-S. In Organic Photochemistry; Padwa, A., Ed.; Marcel Dekker: New York, 1991; Vol. 11, Chapter 4, (b) Wagner, P. J. Acc. Chem. Res. 1989, 22, 83.
6. Reviews: (a) Wagner, P.; Park, B.-S. In Organic Photochemistry; Padwa, A., Ed.; Marcel Dekker: New York, 1991; Vol. 11, Chapter 4, (b) Wagner, P. J. Acc. Chem. Res. 1989, 22, 83.
7. singlet ratios in benne: 3,1 (2), 6.9 (3), 2.7 (4). Photolysis of the salts in solution leads to product ratios that are essentially anion independent and very similar to those quoted above for the free amine.
8. 1: a = 10.209(1) Å. b = 8.6709-(6) A, c = 10.972(1) A; β= 104.675(9)°: Z = 2; R = 3.9%. This structure is disordered in the niacrocycle. X-ray crystallographic refinement of the populations gives a ratio of 72:28 for the two conformers (see text).
9. While crystallographic data obviously do not provide exact information on the situation in the excited state or in the biradical, there is every reason to believe that crystal structure-solid-state reactivity correlations for the Norrish/Yang reaction are approximately correct and can be used in a predictive sense. See: (a) Scheffer, J. R. In Organic Solid State Chemistry; Desiraju, G. R., Ed.; Elsevier: New York, 1987: Chapter 1. (b) Ihmels, H.; Scheffer, J. R. Tetrahedron 1999, 55, 885.
10. While crystallographic data obviously do not provide exact information on the situation in the excited state or in the biradical, there is every reason to believe that crystal structure-solid-state reactivity correlations for the Norrish/Yang reaction are approximately correct and can be used in a predictive sense. See: (a) Scheffer, J. R. In Organic Solid State Chemistry; Desiraju, G. R., Ed.; Elsevier: New York, 1987: Chapter 1. (b) Ihmels, H.; Scheffer, J. R. Tetrahedron 1999, 55, 885.
11. For a discussion of the conformational analysis of 14-membered ring containing compounds, ace: Keller, T. H.; Neeland, E. G.; Rettig, S.; Trotter, J.; Weiler, L. J. Am. Chem. Soc. 1988, 110, 7858.
12. γ abstraction distance, was found to be 2.74 ± 0.04 Å. See: Gudmundsdottir, A. D.; Lewis, T. J.; Randall, L. H.; Scheffer, J. R.; Rettig, S. J.; Trotter, J.; Wu, C.-H. J. Am. Chem. Soc. 1996, 118, 6167.
13. For related examples of topochemically controlled cyclizations of photochemically generated pre-cis and pre-trans 1,4-biradicals, see ref 10.
14. a energetically prohibitive.
15. For an example of complete discrimination in the type II abstraction of the nearer of two γ-hydrogen atoms whose d values differ by 0.27 Å, see ref 10.
16. c. An alternative scenario is one in which the 44% ee is the accidental result of the minor conformer reacting more efficiently (more favorable abstraction parameters) than the major one, but with less than 100% enantioselectivity. Regardless of the details, it is clear that competing reactions from independent conformers are responsible for the low ee.
17. For reviews on methods of asymmetric induction in organic photochemistry, see: (a) Inoue, Y. Chem. Rev. 1992, 92, 741. (b) Rau, H. Chem. Rev. 1983, 83, 535.
18. For reviews on methods of asymmetric induction in organic photochemistry, see: (a) Inoue, Y. Chem. Rev. 1992, 92, 741. (b) Rau, H. Chem. Rev. 1983, 83, 535.