Ketene Dithioacetals in the Aza-Diels-Alder Reaction with N-Arylimines: A Versatile Approach to Tetrahydroquinolines, 2,3-Dihydro-4-quinolones, and 4-Quinolones

Organic Letters

Volumn 4, Issue 25, 2002, Pages 4411-4414

  Cheng, Dai ^a   Zhou, Jinglan ^a   Saiah, Eddine ^a   Beaton, Graham ^a  

^a Deltagen Research Laboratories   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE;

EID: 0141665549     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol020179d     Document Type: Article

References (44)

1. For reviews on hetero Diels-Alder reactions, see: (a) Boger, D. L.; Weinreb, S. M. Hetero Diels-Alder Methodology in Organic Synthesis; Academic Press: San Diego, 1987. (b) Weinreb, S. M. Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergmon: Oxford, 1991; Vol. 5, p 401.
2. For reviews on hetero Diels-Alder reactions, see: (a) Boger, D. L.; Weinreb, S. M. Hetero Diels-Alder Methodology in Organic Synthesis; Academic Press: San Diego, 1987. (b) Weinreb, S. M. Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergmon: Oxford, 1991; Vol. 5, p 401.
3. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
4. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
5. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
6. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
7. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
8. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
9. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
10. For leading references for aza-Diels-Alder reaction between alkenes and N-arylimines or iminium salts, see: (a) Povarov, L. S. Russ. Chem. Rev. 1967, 36, 56-670. (b) Grieco, P. A.; Bahsas, A. Tetrahedron Lett. 1988, 29, 5855-5858. (c) Mellor, J. M.; Merriman, G. D. Tetrahedron 1995, 51, 6115-6132 and references therein. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Chem. Lett. 1995, 423-424. (e) Kobayashi, S.; Nagayama, S. J. Am. Chem. Soc. 1996, 118, 8977-8978. (f) Narasaka, K.; Shibata, T. Heterocycles 1993, 35 (2), 1039-1053. (g) Crousse, B.; Begue, J.-P.; Bonnet-Delpon, D. J. Org. Chem. 2000, 65, 5009-5013. (h) Sundararajan, G.; Prabagaran, N.; Varghese, B. Org. Lett. 2001, 3, 1973-1976.
11. For a review on the synthesis and applications of 1,2,3,4-tetrahydroquinolines, see: Katritzky, A. R.; Rachwal, S.; Rachwal, B. Tetrahedron 1996, 52, 15031-15070 and references therein.
12. For the most recent developments of tetrahydroquinoline synthesis via other strategies, see: (a) Larock, R. C.; Yang, H.; Pace, P. Tetrahedron Lett. 1998, 39, 1885-1888. (b) Padwa, A.; Brodney, M. A.; Liu, B.; Satake, K.; Wu, T. J. Org. Chem. 1999, 64, 3595-3607. (c) Bunce, R. A.; Herron, D. M.; Johnson, L. B.; Kotturi, S. J. Org. Chem. 2001, 66, 2822-2827.
13. For the most recent developments of tetrahydroquinoline synthesis via other strategies, see: (a) Larock, R. C.; Yang, H.; Pace, P. Tetrahedron Lett. 1998, 39, 1885-1888. (b) Padwa, A.; Brodney, M. A.; Liu, B.; Satake, K.; Wu, T. J. Org. Chem. 1999, 64, 3595-3607. (c) Bunce, R. A.; Herron, D. M.; Johnson, L. B.; Kotturi, S. J. Org. Chem. 2001, 66, 2822-2827.
14. For the most recent developments of tetrahydroquinoline synthesis via other strategies, see: (a) Larock, R. C.; Yang, H.; Pace, P. Tetrahedron Lett. 1998, 39, 1885-1888. (b) Padwa, A.; Brodney, M. A.; Liu, B.; Satake, K.; Wu, T. J. Org. Chem. 1999, 64, 3595-3607. (c) Bunce, R. A.; Herron, D. M.; Johnson, L. B.; Kotturi, S. J. Org. Chem. 2001, 66, 2822-2827.
15. 2c,3 rather than at the 3-position. The ketene dithioacetal approach described in this paper successfully places the phenyl group at the 3-position as demonstrated on product 4a, providing a formally "reversed" substitution pattern.
16. 2O.
17. (a) For a review on the preparations and synthetic applications of ketene dithioacetals, see: Kolb, M. Synthesis 1990, 171-190.
18. (b) Barbero, M.; Cadamuro, S.; Ceruti, M.; Degani, I.; Fochi, R.; Regondi, V. Gazz. Chim. Ital. 1987, 117, 227-235.
19. (c) Bellesia, F.; Boni, M.; Ghelfi, F.; Pagnoni, U. M. J. Heterocycl. Chem. 1994, 31, 1721-1723.
20. There have been reports on ketene dithioacetals in Diels-Aider reactions with other hetero dienes. See, for example: (a) Denmark, S. E.; Sternberg, J. A. J. Am. Chem. Soc. 1986, 108, 8277-8279 and references therein. (b) Tietze, L. F.; Schuffenhauer, A. Eur. J. Org. Chem. 1998, 1629-1637.
21. There have been reports on ketene dithioacetals in Diels-Aider reactions with other hetero dienes. See, for example: (a) Denmark, S. E.; Sternberg, J. A. J. Am. Chem. Soc. 1986, 108, 8277-8279 and references therein. (b) Tietze, L. F.; Schuffenhauer, A. Eur. J. Org. Chem. 1998, 1629-1637.
22. For applications of 4-quinolones, see: (a) Pesci, E. C.; Milbank, J. B. J.; Pearson, J. P.; McKnight, S.; Kende, A. S.; Greenberg, E. P.; Iglewski, B. H. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 11229-11234. (b) Xia, Y.; Yano, Z.-Y.; Xia, P.; Hackl, T.; Hamel, E.; Mauger, A.; Wu, J.-H.; Lee, K.-H. J. Med. Chem. 2001, 44, 3932-3936. (c) Cecchetti, V.; Parolin, C.; Moro, S.; Pecere, T.; Filipponi, E.; Calistri, A.; Tabarrini, O.; Gatto, B.; Palumbo, M.; Fravolini, A.; Palu, G. J. Med. Chem. 2000, 43, 3799-3802. (d) Wang, J.-P.; Raung, S.-L.; Huang, L.-J.; Kuo, S.-C. Biochem. Pharmacol. 1998, 56, 1505-1514. (e) Ruiz, M.; Ortiz, R.; Perello, L.; LaTorre, F.; Server-Carrio, F. J. Inorg. Biochem. 1997, 65, 87-96.
23. For applications of 4-quinolones, see: (a) Pesci, E. C.; Milbank, J. B. J.; Pearson, J. P.; McKnight, S.; Kende, A. S.; Greenberg, E. P.; Iglewski, B. H. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 11229-11234. (b) Xia, Y.; Yano, Z.-Y.; Xia, P.; Hackl, T.; Hamel, E.; Mauger, A.; Wu, J.-H.; Lee, K.-H. J. Med. Chem. 2001, 44, 3932-3936. (c) Cecchetti, V.; Parolin, C.; Moro, S.; Pecere, T.; Filipponi, E.; Calistri, A.; Tabarrini, O.; Gatto, B.; Palumbo, M.; Fravolini, A.; Palu, G. J. Med. Chem. 2000, 43, 3799-3802. (d) Wang, J.-P.; Raung, S.-L.; Huang, L.-J.; Kuo, S.-C. Biochem. Pharmacol. 1998, 56, 1505-1514. (e) Ruiz, M.; Ortiz, R.; Perello, L.; LaTorre, F.; Server-Carrio, F. J. Inorg. Biochem. 1997, 65, 87-96.
24. For applications of 4-quinolones, see: (a) Pesci, E. C.; Milbank, J. B. J.; Pearson, J. P.; McKnight, S.; Kende, A. S.; Greenberg, E. P.; Iglewski, B. H. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 11229-11234. (b) Xia, Y.; Yano, Z.-Y.; Xia, P.; Hackl, T.; Hamel, E.; Mauger, A.; Wu, J.-H.; Lee, K.-H. J. Med. Chem. 2001, 44, 3932-3936. (c) Cecchetti, V.; Parolin, C.; Moro, S.; Pecere, T.; Filipponi, E.; Calistri, A.; Tabarrini, O.; Gatto, B.; Palumbo, M.; Fravolini, A.; Palu, G. J. Med. Chem. 2000, 43, 3799-3802. (d) Wang, J.-P.; Raung, S.-L.; Huang, L.-J.; Kuo, S.-C. Biochem. Pharmacol. 1998, 56, 1505-1514. (e) Ruiz, M.; Ortiz, R.; Perello, L.; LaTorre, F.; Server-Carrio, F. J. Inorg. Biochem. 1997, 65, 87-96.
25. For applications of 4-quinolones, see: (a) Pesci, E. C.; Milbank, J. B. J.; Pearson, J. P.; McKnight, S.; Kende, A. S.; Greenberg, E. P.; Iglewski, B. H. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 11229-11234. (b) Xia, Y.; Yano, Z.-Y.; Xia, P.; Hackl, T.; Hamel, E.; Mauger, A.; Wu, J.-H.; Lee, K.-H. J. Med. Chem. 2001, 44, 3932-3936. (c) Cecchetti, V.; Parolin, C.; Moro, S.; Pecere, T.; Filipponi, E.; Calistri, A.; Tabarrini, O.; Gatto, B.; Palumbo, M.; Fravolini, A.; Palu, G. J. Med. Chem. 2000, 43, 3799-3802. (d) Wang, J.-P.; Raung, S.-L.; Huang, L.-J.; Kuo, S.-C. Biochem. Pharmacol. 1998, 56, 1505-1514. (e) Ruiz, M.; Ortiz, R.; Perello, L.; LaTorre, F.; Server-Carrio, F. J. Inorg. Biochem. 1997, 65, 87-96.
26. For applications of 4-quinolones, see: (a) Pesci, E. C.; Milbank, J. B. J.; Pearson, J. P.; McKnight, S.; Kende, A. S.; Greenberg, E. P.; Iglewski, B. H. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 11229-11234. (b) Xia, Y.; Yano, Z.-Y.; Xia, P.; Hackl, T.; Hamel, E.; Mauger, A.; Wu, J.-H.; Lee, K.-H. J. Med. Chem. 2001, 44, 3932-3936. (c) Cecchetti, V.; Parolin, C.; Moro, S.; Pecere, T.; Filipponi, E.; Calistri, A.; Tabarrini, O.; Gatto, B.; Palumbo, M.; Fravolini, A.; Palu, G. J. Med. Chem. 2000, 43, 3799-3802. (d) Wang, J.-P.; Raung, S.-L.; Huang, L.-J.; Kuo, S.-C. Biochem. Pharmacol. 1998, 56, 1505-1514. (e) Ruiz, M.; Ortiz, R.; Perello, L.; LaTorre, F.; Server-Carrio, F. J. Inorg. Biochem. 1997, 65, 87-96.
27. Soder, L.; Wizinger, R. Helv. Chim. Acta. 1959, 42, 1733-1737 and 1779-1785.
28. For the mechanistic aspect of this type of reactions, see: (a) refs 1a (pp 258-260) and 2c,d,g. (b) Cheng, Y.-S.; Ho, E.; Mariano, P. S.; Ammon, H. L. J. Org. Chem. 1985, 50, 5678-5686. (c) Lucchini, V.; Prato, M.; Scorrano, G.; Stivanello, M.; Valle, G. J. Chem. Soc., Perkin Trans. 2 1992, 259-266. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Synthesis 1995, 1195-1202. (e) Linkert, F.; Laschat, S.; Kotila, S.; Fox, T. Tetrahedron 1996, 52, 955-970.
29. For the mechanistic aspect of this type of reactions, see: (a) refs 1a (pp 258-260) and 2c,d,g. (b) Cheng, Y.-S.; Ho, E.; Mariano, P. S.; Ammon, H. L. J. Org. Chem. 1985, 50, 5678-5686. (c) Lucchini, V.; Prato, M.; Scorrano, G.; Stivanello, M.; Valle, G. J. Chem. Soc., Perkin Trans. 2 1992, 259-266. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Synthesis 1995, 1195-1202. (e) Linkert, F.; Laschat, S.; Kotila, S.; Fox, T. Tetrahedron 1996, 52, 955-970.
30. For the mechanistic aspect of this type of reactions, see: (a) refs 1a (pp 258-260) and 2c,d,g. (b) Cheng, Y.-S.; Ho, E.; Mariano, P. S.; Ammon, H. L. J. Org. Chem. 1985, 50, 5678-5686. (c) Lucchini, V.; Prato, M.; Scorrano, G.; Stivanello, M.; Valle, G. J. Chem. Soc., Perkin Trans. 2 1992, 259-266. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Synthesis 1995, 1195-1202. (e) Linkert, F.; Laschat, S.; Kotila, S.; Fox, T. Tetrahedron 1996, 52, 955-970.
31. For the mechanistic aspect of this type of reactions, see: (a) refs 1a (pp 258-260) and 2c,d,g. (b) Cheng, Y.-S.; Ho, E.; Mariano, P. S.; Ammon, H. L. J. Org. Chem. 1985, 50, 5678-5686. (c) Lucchini, V.; Prato, M.; Scorrano, G.; Stivanello, M.; Valle, G. J. Chem. Soc., Perkin Trans. 2 1992, 259-266. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Synthesis 1995, 1195-1202. (e) Linkert, F.; Laschat, S.; Kotila, S.; Fox, T. Tetrahedron 1996, 52, 955-970.
32. For the mechanistic aspect of this type of reactions, see: (a) refs 1a (pp 258-260) and 2c,d,g. (b) Cheng, Y.-S.; Ho, E.; Mariano, P. S.; Ammon, H. L. J. Org. Chem. 1985, 50, 5678-5686. (c) Lucchini, V.; Prato, M.; Scorrano, G.; Stivanello, M.; Valle, G. J. Chem. Soc., Perkin Trans. 2 1992, 259-266. (d) Kobayashi, S.; Ishitani, H.; Nagayama, S. Synthesis 1995, 1195-1202. (e) Linkert, F.; Laschat, S.; Kotila, S.; Fox, T. Tetrahedron 1996, 52, 955-970.
33. Structure assignments were based on NOE experiments and coupling constants.
34. Back, T. G.; Baron, D. L.; Yang, K. J. Org. Chem. 1993, 58, 2407-2413.
35. Degani, I.; Fochi, R.; Regondi, V. Synthesis 1981, 51-53.
36. For methods of 4-quinolone synthesis, see: (a) Reynolds, G.; Hausner, C. In Organic Syntheses; Wiley & Sons: New York, 1955; Collect. Vol. III., pp 593 and 374. (b) Heindel, N. D.; Kennewell, P. D.; Fish, V. B. J. Heterocycl. Chem. 1969, 6, 77-81 and references therein. (c) Potts, K. T.; Ehlinger, R.; Nichols, W. M. J. Org. Chem. 1975, 40, 2596-2600. (d) Chen, B.-C.; Huang, X.; Wang, J. Synthesis 1987, 482-483.
37. For methods of 4-quinolone synthesis, see: (a) Reynolds, G.; Hausner, C. In Organic Syntheses; Wiley & Sons: New York, 1955; Collect. Vol. III., pp 593 and 374. (b) Heindel, N. D.; Kennewell, P. D.; Fish, V. B. J. Heterocycl. Chem. 1969, 6, 77-81 and references therein. (c) Potts, K. T.; Ehlinger, R.; Nichols, W. M. J. Org. Chem. 1975, 40, 2596-2600. (d) Chen, B.-C.; Huang, X.; Wang, J. Synthesis 1987, 482-483.
38. For methods of 4-quinolone synthesis, see: (a) Reynolds, G.; Hausner, C. In Organic Syntheses; Wiley & Sons: New York, 1955; Collect. Vol. III., pp 593 and 374. (b) Heindel, N. D.; Kennewell, P. D.; Fish, V. B. J. Heterocycl. Chem. 1969, 6, 77-81 and references therein. (c) Potts, K. T.; Ehlinger, R.; Nichols, W. M. J. Org. Chem. 1975, 40, 2596-2600. (d) Chen, B.-C.; Huang, X.; Wang, J. Synthesis 1987, 482-483.
39. For methods of 4-quinolone synthesis, see: (a) Reynolds, G.; Hausner, C. In Organic Syntheses; Wiley & Sons: New York, 1955; Collect. Vol. III., pp 593 and 374. (b) Heindel, N. D.; Kennewell, P. D.; Fish, V. B. J. Heterocycl. Chem. 1969, 6, 77-81 and references therein. (c) Potts, K. T.; Ehlinger, R.; Nichols, W. M. J. Org. Chem. 1975, 40, 2596-2600. (d) Chen, B.-C.; Huang, X.; Wang, J. Synthesis 1987, 482-483.
40. For methods of 2,3-dihydro-4-quinolone synthesis, see: (a) Elderfield, R. C.; Maggiolo, A. J. Am. Chem. Soc. 1949, 78, 1906-1910. (b) Kano, S.; Ebata, T.; Shibuya, S. J. Chem. Soc., Perkin Trans. 1 1980, 2105-2111. (c) Ongania, K.; Hohenlohe-Oehringen, K. Chem. Ber. 1981, 114, 1203-1205. (d) Donnelly, J. A.; Farrell, D. F. J. Org. Chem. 1990, 55, 1757-1761. (c) Nieman, J. A.; Ennis, M. D. J. Org. Chem. 2001, 66, 2175-2177 and references therein.
41. For methods of 2,3-dihydro-4-quinolone synthesis, see: (a) Elderfield, R. C.; Maggiolo, A. J. Am. Chem. Soc. 1949, 78, 1906-1910. (b) Kano, S.; Ebata, T.; Shibuya, S. J. Chem. Soc., Perkin Trans. 1 1980, 2105-2111. (c) Ongania, K.; Hohenlohe-Oehringen, K. Chem. Ber. 1981, 114, 1203-1205. (d) Donnelly, J. A.; Farrell, D. F. J. Org. Chem. 1990, 55, 1757-1761. (c) Nieman, J. A.; Ennis, M. D. J. Org. Chem. 2001, 66, 2175-2177 and references therein.
42. For methods of 2,3-dihydro-4-quinolone synthesis, see: (a) Elderfield, R. C.; Maggiolo, A. J. Am. Chem. Soc. 1949, 78, 1906-1910. (b) Kano, S.; Ebata, T.; Shibuya, S. J. Chem. Soc., Perkin Trans. 1 1980, 2105-2111. (c) Ongania, K.; Hohenlohe-Oehringen, K. Chem. Ber. 1981, 114, 1203-1205. (d) Donnelly, J. A.; Farrell, D. F. J. Org. Chem. 1990, 55, 1757-1761. (c) Nieman, J. A.; Ennis, M. D. J. Org. Chem. 2001, 66, 2175-2177 and references therein.
43. For methods of 2,3-dihydro-4-quinolone synthesis, see: (a) Elderfield, R. C.; Maggiolo, A. J. Am. Chem. Soc. 1949, 78, 1906-1910. (b) Kano, S.; Ebata, T.; Shibuya, S. J. Chem. Soc., Perkin Trans. 1 1980, 2105-2111. (c) Ongania, K.; Hohenlohe-Oehringen, K. Chem. Ber. 1981, 114, 1203-1205. (d) Donnelly, J. A.; Farrell, D. F. J. Org. Chem. 1990, 55, 1757-1761. (c) Nieman, J. A.; Ennis, M. D. J. Org. Chem. 2001, 66, 2175-2177 and references therein.
44. For methods of 2,3-dihydro-4-quinolone synthesis, see: (a) Elderfield, R. C.; Maggiolo, A. J. Am. Chem. Soc. 1949, 78, 1906-1910. (b) Kano, S.; Ebata, T.; Shibuya, S. J. Chem. Soc., Perkin Trans. 1 1980, 2105-2111. (c) Ongania, K.; Hohenlohe-Oehringen, K. Chem. Ber. 1981, 114, 1203-1205. (d) Donnelly, J. A.; Farrell, D. F. J. Org. Chem. 1990, 55, 1757-1761. (c) Nieman, J. A.; Ennis, M. D. J. Org. Chem. 2001, 66, 2175-2177 and references therein.