Self-Sensitized Diastereodifferentiating Z-E Photoisomerization of 3-, 4-, and 5-Benzoyloxycyclooctenes: Intra- versus Intermolecular Photosensitization [1]

Abstract

Upon irradiation at 254 nm, (Z)-3-, 4-, and 5-benzoyloxycyclooctenes (1Z-3Z) efficiently isomerized through intra- and/or intermolecular sensitization to the corresponding diastereomeric E-isomers (1E-3E) with low to moderate diastereomeric excesses (de’s) of up to 43 %. The major diastereomer produced from 1Z was switched from (1R*,3R*)-1E (26 % de) to (1R*,3S*)-1E (-11 % de) by simply increasing the substrate concentration from 1 mM to 50 mM. This unusual switching of product chirality is attributed to the opposite diastereoselectivities for intra- and intermolecular photosensitization. In contrast, 2Z and 3Z did not show such switching behavior, but consistently gave a single diastereomer of up to 9 % and 43 % de, respectively, over a wide range of substrate concentrations (0.04-50 mM), for which totally different mechanisms are responsible. Thus, the intra- and intermolecular sensitizations of 2Z exhibit the same diastereoselectivity, while only the intermolecular sensitization of 3Z can occur as a result of the hindered intramolecular approach of the benzoate substituent to the cyclooctene moiety.

Keywords

cyclooctene - diastereoselectivity - isomerization - photochemistry - self-sensitization

References

• 1 Preliminary report: Inoue T. Matsuyama K. Inoue Y. J. Am. Chem. Soc.  1999,  121:  9877 
• 2 Rau H. Chem. Rev.  1983,  83:  535 
• 3 Inoue Y. Chem. Rev.  1992,  92:  741 
• 4 Pete J.-P. Adv. Photochem.  1996,  21:  135 
• 5 Everitt SRL. Inoue Y. In Organic Molecular Photochemistry   Ramamurthy V. Schanze KS. Marcel Dekker; New York: 1999.  p.71-130  
• 6 Inoue Y. Wada T. Asaoka S. Sato H. Pete J.-P. Chem. Commun.  2000,  251 
• 8 Hayashi T. Tomioka K. Yonemitsu O. Asymmetric Synthesis: Graphical Abstracts and Experimental Methods   Kodansha/Gordon & Breach; Tokyo/Amsterdam: 1998. 
• 9 Gawley RE. Aubè J. In Principles of Asymmetric Synthesis   Baldwin JE. Magnus FRS. Magnus PD. Pergamon; Oxford: 1996. 
• 10 Ager DJ. East MB. Asymmetric Synthetic Methodology   CRC Press; Boca Raton: 1996. 
• 11 Seyden-Penne J. Chiral Auxiliaries and Ligands in Asymmetric Synthesis   Wiley; New York: 1995. 
• 12 Nógrádi M. Stereoselective Synthesis   2nd ed:  VCH; Weinheim: 1995. 
• 13 Noyori R. Asymmetric Catalysis in Organic Synthesis   Wiley; New York: 1994. 
• 14 Wong CH. Whitesides GM. Enzymes in Synthetic Organic Chemistry   Pergamon; Oxford: 1994. 
• 15 Collins AN. Sheldrake GN. Crosby J. Chirality in Industry   Vol. 1/Vol. 2:  Wiley; Chichester: 1992/1997. 
• 16 Sheldon RA. Chirotechnology-Industrial Synthesis of Optically Active Compounds   Marcel Dekker; New York: 1993. 
• 17 Inoue Y. Yokoyama T. Yamasaki N. Tai A. J. Am. Chem. Soc.  1989,  111:  6480 
• 18 Inoue Y. Yamasaki N. Yokoyama T. Tai A. J. Org. Chem.  1992,  57:  1332 
• 19 Inoue Y. Yamasaki N. Yokoyama T. Tai A. J. Org. Chem.  1993,  58:  1011 
• 20a Tsuneishi H. Hakushi T. Tai A. Inoue Y. J. Chem. Soc., Perkin Trans 2  1995,  2057 
• 20b Inoue Y. Tsuneishi H. Hakushi T. Tai A. J. Am. Chem. Soc.  1997,  119:  472 
• 21 Hoffmann R. Inoue Y. J. Am. Chem. Soc.  1999,  121:  10702 
• 22a Asaoka S. Ooi M. Jiang P. Wada T. Inoue Y. J. Chem. Soc., Perkin Trans. 2  2000,  77 
• 22b Asaoka S. Horiguchi H. Wada T. Inoue Y. J. Chem. Soc., Perkin Trans. 2  2000,  737 
• 23 Asaoka S. Kitazawa T. Wada T. Inoue Y. J. Am. Chem. Soc.  1999,  121:  8486 
• 24 Inoue Y. Matsushima E. Wada T. J. Am. Chem. Soc.  1998,  120:  10687 
• 25 Inoue Y. Ikeda H. Kaneda M. Sumimura T. Everitt SRL. Wada T. J. Am. Chem. Soc.  2000,  122:  406 
• 26 We have reported a similar intramolecular photosensitized diastereodifferentiating isomerization of 1-alkoxymethyl-cyclooctene derivatives tethered to a benzenecarboxylate chromophore with an enantiopure pentane-2,4-diyl bridge. Possessing a long flexible tether, these cyclooctenes efficiently undergo the intramolecular photosensitization to give the corresponding diastereomeric Z-isomers in high photostationary-state Z/E ratios of up to 0.8 for the benzoate derivative at 25 °C and moderate diastereomeric excesses of up to 44 % for the terephthalate derivative at -65 °C: Sugimura T. Shimizu H. Umemoto S. Tsuneishi H. Hakushi T. Inoue Y. Tai A. Chem. Lett.  1998,  323 
• 28 Yamasaki N. Inoue Y. Yokoyama T. Tai A. Ishida A. Takamuku S. J. Am. Chem. Soc.  1991,  113:  1933 
• 29 Tsuneishi H. Hakushi T. Inoue Y. J. Chem. Soc., Perkin Trans. 2  1996,  1601 
• 30 Whitham GH. Wright M. J. Chem. Soc. (C)  1971,  883 
• 32 Koltun WL. Biopolymers  1965,  3:  665 
• 33 Inoue Y. Takamuku S. Kunitomi Y. Sakurai H. J. Chem. Soc., Perkin Trans. 2  1980,  1672 
• 34 Cope AC. Estes LL. J. Am. Chem. Soc.  1950,  72:  1129 
• 35 Crandall JK. Banks DB. Colyer RA. Watkins RJ. Arrington JP. J. Org. Chem.  1968,  33:  423 
• 36 Hatchard CG. Parker CA. Proc. R. Soc. London, Ser. A  1956,  235A:  518 
• 37 Vesley GF. Mol. Photochem.  1971,  3:  193 

7

Inoue Y., Sugahara N., Wada T.; Pure Appl. Chem.; in press

27

The asterisk represents the relative configuration of the two stereogenic centers

31

We reported the opposite configuration in our previous paper, [1] which is erroneous and should be corrected