Specific and chemoselective multi-α-arylation reaction of benzoylformic acid with or without decarbonylation in P2O5-MsOH and related acidic media

Journal of Organic Chemistry

Volumn 65, Issue 4, 2000, Pages 941-944

  Yonezawa, Noriyuki ^a   Hino, Tetsuo ^a,b   Matsuda, Kazuhisa ^a,c   Matsuki, Toshiyuki ^a,c   Narushima, Daisuke ^a   Kobayashi, Masato ^a   Ikeda, Tomiki ^a,b  

^a TOKYO UNIVERSITY OF AGRICULTURE AND TECHNOLOGY   (Japan)

^b TOKYO INSTITUTE OF TECHNOLOGY   (Japan)

^c GUNMA UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

ACID ANHYDRIDE; BENZOPHENONE DERIVATIVE; CARBOXYLIC ACID; MESYLIC ACID; PHENYLGLYOXYLIC ACID; PHOSPHORUS PENTOXIDE;

ACYLATION; ARTICLE; CHEMICAL REACTION; CHEMICAL STRUCTURE; ELECTRON TRANSPORT; SOLUBILIZATION;

EID: 0034712217     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo990524l     Document Type: Article

References (48)

1. Olah, G. A. Friedel-Crafts and Related Reaction; Wiley-Interscience: New York, 1964; Vol. 3. Olah, G. A.; Molnár, Á. Hydrocarbon Chemistry; Wiley-Interscience: New York, 1995; p 141.
2. Olah, G. A. Friedel-Crafts and Related Reaction; Wiley-Interscience: New York, 1964; Vol. 3. Olah, G. A.; Molnár, Á. Hydrocarbon Chemistry; Wiley-Interscience: New York, 1995; p 141.
3. For a review, see: Yonezawa, N.; Hino, T.; Ikeda, T. Recent Res. Dev. Synth. Org. Chem. 1998, 1, 213 and reference cited therein.
4. For example: (a) Isumi, J.; Mukaiyama, T. Chem. Lett. 1996, 739. (b) Suzuki, K.; Kitagawa, H.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1993, 66, 3729. (c) Hachiya, I.; Moriwaki, M.; Kobayashi, S. Tetrahedron Lett. 1995, 36, 409. (d) Mukaiyama, T.; Ohno, T.; Nishimura, T.; Suda, S.; Kobayashi, S. Chem. Lett. 1991, 1059. (e) Desmurs, J. R.; Labrouillère, M.; Roux, C. Le; Gaspard, H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38, 8871.
5. For example: (a) Isumi, J.; Mukaiyama, T. Chem. Lett. 1996, 739. (b) Suzuki, K.; Kitagawa, H.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1993, 66, 3729. (c) Hachiya, I.; Moriwaki, M.; Kobayashi, S. Tetrahedron Lett. 1995, 36, 409. (d) Mukaiyama, T.; Ohno, T.; Nishimura, T.; Suda, S.; Kobayashi, S. Chem. Lett. 1991, 1059. (e) Desmurs, J. R.; Labrouillère, M.; Roux, C. Le; Gaspard, H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38, 8871.
6. For example: (a) Isumi, J.; Mukaiyama, T. Chem. Lett. 1996, 739. (b) Suzuki, K.; Kitagawa, H.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1993, 66, 3729. (c) Hachiya, I.; Moriwaki, M.; Kobayashi, S. Tetrahedron Lett. 1995, 36, 409. (d) Mukaiyama, T.; Ohno, T.; Nishimura, T.; Suda, S.; Kobayashi, S. Chem. Lett. 1991, 1059. (e) Desmurs, J. R.; Labrouillère, M.; Roux, C. Le; Gaspard, H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38, 8871.
7. For example: (a) Isumi, J.; Mukaiyama, T. Chem. Lett. 1996, 739. (b) Suzuki, K.; Kitagawa, H.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1993, 66, 3729. (c) Hachiya, I.; Moriwaki, M.; Kobayashi, S. Tetrahedron Lett. 1995, 36, 409. (d) Mukaiyama, T.; Ohno, T.; Nishimura, T.; Suda, S.; Kobayashi, S. Chem. Lett. 1991, 1059. (e) Desmurs, J. R.; Labrouillère, M.; Roux, C. Le; Gaspard, H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38, 8871.
8. For example: (a) Isumi, J.; Mukaiyama, T. Chem. Lett. 1996, 739. (b) Suzuki, K.; Kitagawa, H.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1993, 66, 3729. (c) Hachiya, I.; Moriwaki, M.; Kobayashi, S. Tetrahedron Lett. 1995, 36, 409. (d) Mukaiyama, T.; Ohno, T.; Nishimura, T.; Suda, S.; Kobayashi, S. Chem. Lett. 1991, 1059. (e) Desmurs, J. R.; Labrouillère, M.; Roux, C. Le; Gaspard, H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38, 8871.
9. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
10. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
11. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
12. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
13. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
14. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
15. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
16. For example: (a) Kodomari, M.; Suzuki, Y.; Yoshida, K. Chem. Commun. 1997, 1567. (b) Clark, J. H.; Kybett, A. P.; Macquarrie, D. J. H.; Barlow, S. J.; Landon, P. J. Chem. Soc., Chem. Commun. 1985, 1353. (c) Barlow, S. J.; Clark, J. H.; Darby, M. R.; Kybett, A. P.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1991, 74. (d) Bastock, T. W.; Clark, J. H.; Landon, P.; Martin, K. J. Chem. Res. Synop. 1994, 104. (e) Chiche, B.; Finiels, A.; Gauthier, C.; Geneste, P. J. Org. Chem. 1986, 51, 212. (f) Wang, Q. L.; Ma, Y.; Ji, X.; Yan, H.; Qiu, Q. J. Chem. Soc., Chem. Commun. 1995, 2307. (g) Ranu, B. C.; Ghosk, K.; Jana, U. J. Org. Chem. 1996, 61, 9546. (h) Miller, J. M.; Wails, D.; Hartman, J. S.; Schebesh, K.; Belelie, J. L. Can. J. Chem. 1998, 76, 382.
17. TfOH is defined as a superacidic medium by Olah. See: (a) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Science 1979, 206, 13. (b) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Superacids; Wiley: New York, 1985. (c) Saito, S.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc. 1995, 117, 11081. (d) Saito, S.; Ohwada, T.; Shudo, K. J. Org. Chem. 1996, 61, 8089. (e) Olah, G. A.; Rasul, G.; York, C.; Prakash, G. K. S. J. Am. Chem. Soc. 1995, 117, 11211.
18. TfOH is defined as a superacidic medium by Olah. See: (a) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Science 1979, 206, 13. (b) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Superacids; Wiley: New York, 1985. (c) Saito, S.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc. 1995, 117, 11081. (d) Saito, S.; Ohwada, T.; Shudo, K. J. Org. Chem. 1996, 61, 8089. (e) Olah, G. A.; Rasul, G.; York, C.; Prakash, G. K. S. J. Am. Chem. Soc. 1995, 117, 11211.
19. TfOH is defined as a superacidic medium by Olah. See: (a) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Science 1979, 206, 13. (b) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Superacids; Wiley: New York, 1985. (c) Saito, S.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc. 1995, 117, 11081. (d) Saito, S.; Ohwada, T.; Shudo, K. J. Org. Chem. 1996, 61, 8089. (e) Olah, G. A.; Rasul, G.; York, C.; Prakash, G. K. S. J. Am. Chem. Soc. 1995, 117, 11211.
20. TfOH is defined as a superacidic medium by Olah. See: (a) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Science 1979, 206, 13. (b) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Superacids; Wiley: New York, 1985. (c) Saito, S.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc. 1995, 117, 11081. (d) Saito, S.; Ohwada, T.; Shudo, K. J. Org. Chem. 1996, 61, 8089. (e) Olah, G. A.; Rasul, G.; York, C.; Prakash, G. K. S. J. Am. Chem. Soc. 1995, 117, 11211.
21. TfOH is defined as a superacidic medium by Olah. See: (a) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Science 1979, 206, 13. (b) Olah, G. A.; Prakash, G. K. S.; Sommer, J. Superacids; Wiley: New York, 1985. (c) Saito, S.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc. 1995, 117, 11081. (d) Saito, S.; Ohwada, T.; Shudo, K. J. Org. Chem. 1996, 61, 8089. (e) Olah, G. A.; Rasul, G.; York, C.; Prakash, G. K. S. J. Am. Chem. Soc. 1995, 117, 11211.
22. Effengerger, F.; Epple, G. Angew. Chem., Int. Ed. Engl. 1972, 11, 299.
23. 5-MsOH is a convenient alternative to PPA because of its reduced viscosity and circumstantially better solvent power. See: Eaton, P. E.; Carson, G. R.; Lee, J. T. J. Org. Chem. 1973, 38, 4071.
24. (a) Ueda, M. Synlett 1992, 605.
25. (b) Yonezawa, N.; Namie, T.; Ikezaki, T.; Hino, T.; Nakamura, H.; Tokita, Y.; Katakai, R. React. Funct. Polym. 1996, 30, 261.
26. (c) So, Y. H.; Heeschen, J. P. J. Org. Chem. 1997, 62, 3552.
27. 5-MsOH: (a) Yonezawa, N.; Tokita, Y.; Hino, T.; Nakamura, H.; Katakai, R. J. Org. Chem. 1996, 61, 3551. (b) Yonezawa, N.; Hino, T.; Tokita, Y.; Matsuda, K.; Ikeda, T. Tetrahedron 1997, 42, 14287. (c) Yonezawa, N.; Hino, T.; Ikeda, T. Recent Res. Dev. Synth. Org. Chem. 1998, 1, 213. (d) Yonezawa, N.; Hino, T.; Shimizu, M.; Matsuda, K.; Ikeda, T. J. Org. Chem. 1999, 64, 4179.
28. 5-MsOH: (a) Yonezawa, N.; Tokita, Y.; Hino, T.; Nakamura, H.; Katakai, R. J. Org. Chem. 1996, 61, 3551. (b) Yonezawa, N.; Hino, T.; Tokita, Y.; Matsuda, K.; Ikeda, T. Tetrahedron 1997, 42, 14287. (c) Yonezawa, N.; Hino, T.; Ikeda, T. Recent Res. Dev. Synth. Org. Chem. 1998, 1, 213. (d) Yonezawa, N.; Hino, T.; Shimizu, M.; Matsuda, K.; Ikeda, T. J. Org. Chem. 1999, 64, 4179.
29. 5-MsOH: (a) Yonezawa, N.; Tokita, Y.; Hino, T.; Nakamura, H.; Katakai, R. J. Org. Chem. 1996, 61, 3551. (b) Yonezawa, N.; Hino, T.; Tokita, Y.; Matsuda, K.; Ikeda, T. Tetrahedron 1997, 42, 14287. (c) Yonezawa, N.; Hino, T.; Ikeda, T. Recent Res. Dev. Synth. Org. Chem. 1998, 1, 213. (d) Yonezawa, N.; Hino, T.; Shimizu, M.; Matsuda, K.; Ikeda, T. J. Org. Chem. 1999, 64, 4179.
30. 5-MsOH: (a) Yonezawa, N.; Tokita, Y.; Hino, T.; Nakamura, H.; Katakai, R. J. Org. Chem. 1996, 61, 3551. (b) Yonezawa, N.; Hino, T.; Tokita, Y.; Matsuda, K.; Ikeda, T. Tetrahedron 1997, 42, 14287. (c) Yonezawa, N.; Hino, T.; Ikeda, T. Recent Res. Dev. Synth. Org. Chem. 1998, 1, 213. (d) Yonezawa, N.; Hino, T.; Shimizu, M.; Matsuda, K.; Ikeda, T. J. Org. Chem. 1999, 64, 4179.
31. Yonezawa, N.; Hino, T.; Kinuno, T.; Matsuki, T.; Ikeda, T. Synth. Commun. 1999, 29, 1687.
32. +-[P] (which had very stable arenium-type resonance structures) to afford phenone 7a after hydrolysis.
33. 5-MsOH mediated specific decarbonylative α,α-diarylation of 2-methoxypropanoic acid, giving 1,1-diarylethane and 1,1-diarylethene, was concluded to proceed only after the formation of carboxylic-phosphoric anhydride at the initial step.
34. Because the resultant cation 13 from an α-monoarylated intermediate is highly electrophilic, the second α-arylation is considered to proceed more readily. In contrast, the first α,α-arylation in TFA is hardly even considered to proceed at 60 °C (Table 1, run 2).
35. +-[P] derived from arene 2d. This is due to the 1,4-substitution pattern and, consequently, its lack of selectivity when reacting with the nucleophile in the last step (see Scheme 2). On the other hand, we supposed that the lower reactivity of the arene (2d), than that of other dimethoxybenzene isomers, should give rise to the lack of selectivity. (Matrix presented)
36. Decarbonylation of α,α-trisubstituted carboxylic acids: (a) Gillespie, R. J. J. Chem. Soc. 1950, 2997. (b) Burton, H.; Praill, P. F. G. J. Chem. Soc. 1951, 726.
37. Decarbonylation of α,α-trisubstituted carboxylic acids: (a) Gillespie, R. J. J. Chem. Soc. 1950, 2997. (b) Burton, H.; Praill, P. F. G. J. Chem. Soc. 1951, 726.
38. 3: (a) March, J. Advanced Organic Chemistry, Reaction, Mechanisms, and Structure, 3rd ed.; Wiley-Interscience: New York, 1985. (b) Wegmann, J.; Dahn, H. Helv. Chim. Acta 1946, 29, 415.
39. 3: (a) March, J. Advanced Organic Chemistry, Reaction, Mechanisms, and Structure, 3rd ed.; Wiley-Interscience: New York, 1985. (b) Wegmann, J.; Dahn, H. Helv. Chim. Acta 1946, 29, 415.
40. 4 and TfOH: (a) Olah, G. A. Friedel-Crafts and Related Reaction; Wiley-Interscience: New York, 1964, Vol. 2, pp 597-640. (b)Yamazaki, T.; Saito, S.; Ohwada, T.; Shudo, K. Tetrahedron Lett. 1995, 36, 5749.
41. 4 and TfOH: (a) Olah, G. A. Friedel-Crafts and Related Reaction; Wiley-Interscience: New York, 1964, Vol. 2, pp 597- 640. (b)Yamazaki, T.; Saito, S.; Ohwada, T.; Shudo, K. Tetrahedron Lett. 1995, 36, 5749.
42. The predominant formation of phenones 7d-h in the reactions with arenes 2d-h at 60 °C indicates that the relative nucleophilicity of phosphoryloxy moiety (O-[P]) in the reaction system, after the first arylation, is enhanced to a level able to overcome the second arylation (Table 1, runs 16, 18, 20, 22, 24).
43. Our consideration about the main reaction pathway is that a stepwise manner, via cation intermediates formed by the elimination of carbon monoxide, should somewhat implausible, because such cations will be too inert to propagate electrophilic aromatic substitution reactions. On the other hand, one of the reviewers insisted that the stepwise manner was best one when arenium ions were involved.
44. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.
45. For this extraction procedure, ether is not an effective solvent. Aromatic solvents are more suitable. We have ascertained that toluene, the solvent preferred over benzene, is also employable without causing a large drop in efficiency.
46. Hellwinkel, D.; Heidelberg, U. Chem. Ber. 1989, 2351.
47. 1H FT-NMR Spectra; Aldrich Chemical: Milwaukee, 1992.
48. Ottenheijm, H. C. J.; de Man, J. H. M. Synthesis 1975, 163.