Thermal and photochemical transformation of conformational chirality into configurational chirality in the crystalline state

Journal of the American Chemical Society

Volumn 125, Issue 14, 2003, Pages 4040-4041

  Chong, Kenneth C W ^a   Scheffer, John R ^a  

^a UNIVERSITY OF BRITISH COLUMBIA   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

ACETONITRILE; BENZOIC ACID DERIVATIVE; KETONE DERIVATIVE; METHYL 4 ACETYLBENZOATE; NAPHTHALENE DERIVATIVE; UNCLASSIFIED DRUG;

ARTICLE; CHIRALITY; CRYSTAL STRUCTURE; ENANTIOSELECTIVITY; PHOTOCHEMISTRY; PHOTOLYSIS; REACTION ANALYSIS; STRUCTURE ANALYSIS; THERMAL ANALYSIS;

EID: 0037427292     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja029182i     Document Type: Article

References (16)

1. (a) Vaida, M.; Popvitz-Biro, R.; Leiserowitz, L.; Lahav, M. In Photochemistry in Organized and Constrained Media; Ramamurthy, V., Ed.; VCH: New York, 1991: pp 247-302.
2. (b) Scheffer, J. R. Can. J. Chem. 2001, 79, 349 and references therein.
3. (c) Tanaka, K.; Miyamoto, H.; Toda, F. In Molecular and Supramolecular Photochemistry; Ramamurthy, V., Schanze, K. S., Eds.; Marcel Dekker: New York, 2001; Vol. 8, pp 385-425.
4. (d) Sakamoto, M. Chem. Eur. J. 1997, 3, 684.
5. Tanaka, K.; Toda, F. Chem. Rev. 2000, 100, 1025 and references therein.
6. For an introduction to the use of ionic auxiliaries 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.
7. For the synthesis of compound 1a, see Supporting Information.
8. Owing to the relief of cyclopropane ring strain. Norrish type II cleavage is favored over Yang cyclization in the case of compounds of general structure 1. For a discussion of the Norrish type II chemistry of cyclopropyl ketones, see: Dauben W. G.; Schutte, L.; Wolf, R. E. J. Org. Chem. 1969, 34, 6273; For a review of the Norrish/Yang type II reaction, see: Wagner, P. J.; Park, B.-S. In Organic Photochemistry; Padwa, A., Ed.; Marcel Dekker: New York, 1991; Vol. 11, Chapter 4.
9. Owing to the relief of cyclopropane ring strain. Norrish type II cleavage is favored over Yang cyclization in the case of compounds of general structure 1. For a discussion of the Norrish type II chemistry of cyclopropyl ketones, see: Dauben W. G.; Schutte, L.; Wolf, R. E. J. Org. Chem. 1969, 34, 6273; For a review of the Norrish/Yang type II reaction, see: Wagner, P. J.; Park, B.-S. In Organic Photochemistry; Padwa, A., Ed.; Marcel Dekker: New York, 1991; Vol. 11, Chapter 4.
10. Roberts, R. M.; Landolt, R. G.; Greene, R. N.; Heyer, E. W. Am. Chem. Soc. 1967, 89, 1404.
11. To date, all attempts to determine the X-ray crystal structures of salts 1c-1h have not met with success. Because most compounds crystallize in or near their minimum-energy conformations, the analysis in this case is based on the calculated structure shown in Figure 1.
12. For a similar situation in which the enantioselectivity of Yang photocyclization in the crystalline state is governed by preferential abstraction of the geometrically favored γ-hydrogen atom, see: Leibovitch, M.; Olovvson, G.; Scheffer, J. R.; Trotter, J. J. Am. Chem. Soc. 1998, 120, 12755. The preference for abstraction of Ha over Hb in the case of ketones of general structure 1 is in accord with previous work from our laboratory on the geometric requirements for type II hydrogen transfer. See: Ihmels, H.; Scheffer, J. R. Tetrahedron 1999, 55, 885.
13. For a similar situation in which the enantioselectivity of Yang photocyclization in the crystalline state is governed by preferential abstraction of the geometrically favored γ-hydrogen atom, see: Leibovitch, M.; Olovvson, G.; Scheffer, J. R.; Trotter, J. J. Am. Chem. Soc. 1998, 120, 12755. The preference for abstraction of Ha over Hb in the case of ketones of general structure 1 is in accord with previous work from our laboratory on the geometric requirements for type II hydrogen transfer. See: Ihmels, H.; Scheffer, J. R. Tetrahedron 1999, 55, 885.
14. Because the photochemical ee's were necessarily determined under conditions where the thermal reaction was immeasurably slow, direct comparison of the thermal and photochemical ee's at the same temperature and conversion was not possible.
15. 1H NMR spectrum.
16. In agreement with this picture, the ee obtained by heating salt 1c to >98% conversion at 52-56 °C (36%) was nearly twice that obtained at 90-95 °C (20%). For a discussion of crystalline state thermal reactions, see: Paul, I. C.; Curtin, D. Y. Acc. Chem. Res. 1973, 6, 217.