8656
T. Maki et al. / Tetrahedron 63 (2007) 8645–8657
96 MHz) d 29.1; 13C NMR (CDCl3, 75 MHz) d 117.0 (2C),
127.8 (2C), 143.7 (2C).
Ohara, S.; Yamamoto, H. Org. Synth. 2002, 79, 176–185; (d)
Maki, T.; Ishihara, K.; Yamamoto, H. Synlett 2004, 1355–
1358; (e) Ishihara, K.; Kondo, S.; Yamamoto, H. Synlett
2001, 1371–1374.
4.14. Typical procedure for the amide condensation
reaction of an equimolar mixture of carboxylic acids
and amines catalyzed by 4b (Table 13)
4. Maki, T.; Ishihara, K.; Yamamoto, H. Org. Lett. 2005, 7, 5043–
5046.
5. Maki, T.; Ishihara, K.; Yamamoto, H. Org. Lett. 2005, 7, 5047–
5050.
6. Maki, T.; Ishihara, K.; Yamamoto, H. Org. Lett. 2006, 8, 1431–
1434.
A dry, 20-mL round-bottom flask equipped with a Teflon-
coated magnetic stirring bar and a Dean–Stark apparatus sur-
mounted by a reflux condenser was charged with carboxylic
acids (2.0 mmol), amines (2.0 mmol), and 4b (26 mg,
0.10 mmol, 5.0 mol %) in toluene or o-xylene (10 mL).
The mixture was brought to heat at azeotropic reflux with
the removal of water. After the reaction was completed,
the resulting mixture was cooled to ambient temperature
and washed with both aqueous solutions of ammonium chlo-
ride and sodium hydrogen carbonate, and the product was
extracted with ethyl acetate. The combined organic layers
were dried over magnesium sulfate. The solvent was evapo-
rated, and the residue was purified by column chromato-
graphy on silica gel to give the desired amides.
7. (a) Ohara, S.; Ishihara, K.; Yamamoto, H. The 77th Spring
Meeting of Chem. Soc. Jpn., 2000; (b) Ishihara, K.;
Yamamoto, H. Jpn. Kokai Tokkyo Koho JP 270939, 2001
(2001-10-02); Application: JP 87495, 2000 (2000-03-27).
8. Latta, R.; Springsteen, G.; Wang, B. Synthesis 2001, 1611–
1613.
9. (a) Ishiyama, T.; Ishida, K.; Miyaura, N. Tetrahedron 2001, 57,
9813–9816; (b) Bouillon, A.; Lancelot, J.-C.; de Oliveria
Santos, J. S.; Collot, V.; Bovy, P. R.; Rault, S. Tetrahedron
2003, 59, 10043–10049; (c) Gros, P.; Doudouth, A.; Fort, Y.
Tetrahedron Lett. 2004, 45, 6239–6241.
10. According to the report by Wang and co-workers,8 the amide
condensation of less-reactive benzoic acid (1 equiv) with benz-
ylamine (1.2 equiv) gave the product in 92% isolated yield in
the presence of 1 mol % of 3-pyridineboronic acid or 5 in
toluene. However, we could not duplicate Wang’s results, and
obtained the amide in less than 10% yield under the same
conditions.
11. Houston, T. A.; Wilkinson, B. L.; Blanchfield, J. T. Org. Lett.
2004, 6, 679–681.
12. Tertiary alcohols were not condensed with a-hydroxycarb-
oxylic acids.
4.15. Typical procedure for Ritter reaction catalyzed by
4c (Table 14)
A dry, 10-mL round-bottom flask equipped with a Teflon-
coated magnetic stirring bar and a reflux condenser was
charged with B(OH)3 (6.2 mg, 0.10 mmol), tetrachlorocate-
chol (50 mg, 0.20 mmol), and benzylic alcohols (2.0 mmol)
in nitriles (5 mL). The mixture was brought to reflux. After
the reaction was completed, the resulting mixture was
cooled to ambient temperature and washed with an aqueous
solution of sodium hydrogen carbonate, and the product was
extracted with ethyl acetate. The combined organic layers
were dried over magnesium sulfate. The solvent was evapo-
rated, and the residue was purified by column chromato-
graphy on silica gel to give the desired amides.
13. After the reaction, 3a must be washed with 1 M HCl aqueous
solution. Without this manipulation, the catalytic activity of
3a is diminished.
14. (a) Babcock, L.; Pizer, R. Inorg. Chem. 1980, 19, 56–61; (b)
ꢀ
Lamande, L.; Boyer, D.; Munoz, A. J. Organomet. Chem.
ꢀ
ꢀ
1987, 329, 1–29; (c) Bello-Ramırez, M. A.; Martınez,
M. E. R.; Flores-Parra, A. Heteroat. Chem. 1993, 4, 613; (d)
Pizer, R.; Ricatto, P. J. Inorg. Chem. 1994, 33, 2402–2406.
15. It is not clear whether 11 or 12 is the more active intermediate.
16. Collum, D. B.; Chen, S.; Ganem, B. J. Org. Chem. 1978, 43,
4393–4394.
LBA 4c: 11B NMR (DMSO-d6, 96 MHz) d 14.7; 13C NMR
(DMSO-d6, 75 MHz) d 111.7 (4C), 120.3 (4C), 147.6 (4C).
Acknowledgements
17. (a) Ishihara, K.; Yamamoto, H. J. Am. Chem. Soc. 1994, 116,
1561–1562; (b) Ishihara, K.; Miyata, M.; Hattori, K.; Tada,
T.; Yamamoto, H. J. Am. Chem. Soc. 1994, 116, 10520–
10524; (c) Ishihara, K.; Kurihara, H.; Yamamoto, H. J. Am.
Chem. Soc. 1996, 118, 3049–3050; (d) Ishihara, K.; Kondo,
S.; Kurihara, H.; Yamamoto, H. J. Org. Chem. 1997, 62,
3026–3027; (e) Ishihara, K.; Kurihara, H.; Matsumoto, M.;
Yamamoto, H. J. Am. Chem. Soc. 1998, 120, 6920–6930.
18. (a) Tang, P. Org. Synth. 2005, 81, 262–272; (b) Arnold, K.;
Davies, B.; Giles, R. L.; Grosjean, C.; Smith, G. E.; Whiting,
A. Adv. Synth. Catal. 2006, 348, 813–820. In this paper,
Whiting and co-workers reported that o-(N,N-diisopropyl-
aminomethyl)benzeneboronic acid was more effective for the
amide condensation reaction of benzoic acid than boric acid
and 3,4,5-trifluorobenzeneboronic acid.
We thank Dr. M. Hatano (Nagoya University) for performing
X-ray single-crystal analysis. Financial support for this pro-
ject was provided by SORST and Research for Promoting
Technological Seeds from JST, the 21st Century COE Pro-
gram of MEXT, and the Iwatani Naoji Foundation. T.M.
also acknowledges a JSPS Fellowship for Japanese Junior
Scientists.
References and notes
1. Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and
Practice; Oxford University: Oxford, 1988.
2. Benz, G. Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: New York, NY, 1991; Vol. 6,
p 323.
3. (a) Ishihara, K.; Ohara, S.; Yamamoto, H. J. Org. Chem. 1996,
61, 4196–4197; (b) Ishihara, K.; Ohara, S.; Yamamoto, H.
Macromolecules 2000, 33, 3511–3513; (c) Ishihara, K.;
19. 4,5,6,7-Tetrafluoro- and 4,5,6,7-tetrabromobenzo[d][1,3,2]-
dioxaborol-2-ols could not be isolated by distillation tech-
niques.
€
20. Lang, A.; Noth, H.; Thomann-Albach, M. Chem. Ber./Recueil.
1997, 130, 363–369. In this paper, 4b was prepared from