438
Vol. 57, No. 4
(1999).
5) Kataoka N., Shelby Q., Stambuli J. P., Hartwig J. F., J. Org. Chem., 67,
5553—5566 (2002).
6) Anderson K. W., Mendez-Perez M., Priego J., Buchwald S. L., J. Org.
Chem., 68, 9563—9573 (2003).
7) Zim D., Buchwald S. L., Org. Lett., 5, 2413—2415 (2003).
8) Strieter E. R., Buchwald S. L., Angew. Chem. Int. Ed., 45, 925—928
(2006).
9) Au S.-M., Huang J.-S., Che C.-M., Yu W.-Y., J. Org. Chem., 65,
7858—7864 (2000).
10) Tsang W. C. P., Zheng N., Buchwald S. L., J. Am. Chem. Soc., 127,
14560—14561 (2005).
11) Ullmann F., Ber. Dtsch. Chem. Ges., 36, 2382—2384 (1903).
12) Beletskaya I. P., Cheprakov A. V., Coordination Chem. Rev., 248,
2337—2364 (2004).
Chart 2. Possible Mechanism
13) Ley S. V., Thomas A. W., Angew. Chem. Int. Ed., 42, 5400—5449
(2003).
14) Finet J.-P., Fedrov A. Y., Combes S., Boyer G., Current Org. Chem., 6,
597—626 (2002).
15) Yamamoto T., Kurata Y., Can. J. Chem., 61, 86—91 (1983).
16) Lam P. Y. S., Clark C. G., Saubern S., Adams J., Winters M. P., Chan
D. M. T., Combs A., Tetrahedron Lett., 39, 2941—2944 (1998).
17) Chan D. M. T., Monaco K. L., Wang R.-P., Winters M. P., Tetrahedron
Lett., 39, 2933—2936 (1998).
cept for t-butyl- (6e) and diphenylamines (6p). The fact that
no formation of triphenylamine from 6p is in good accor-
dance with the observation that only mono-phenylated prod-
uct of amines was formed in the present reaction.
Exact mechanism of this Sb-mediated N-arylation is un-
clear at present. We considered that a similar mechanism for
diaryliodonium salts by Lockhart36) and for lead(VI)22) and
bismuth(V)23) compounds by Barton et al. could be applica-
ble to our Sb-mediated N-arylation (Chart 2).
The first step of the reaction would be the generation of
Cu(I) species (A) by reduction of Cu(OAc)2 with amine or
excess TEA. The intermediate A thus formed reacts with
amine to give Cu(I)L2NHR (B). Oxidative addition of
Ar4SbOAc to B affords Cu(III) intermediate (C) which leads
to Cu(III) complex (D) accompanied by elimination of
Ar3Sb. This intermediate (D) successively undergoes reduc-
tive elimination to give the final product (E) with regenera-
tion of the Cu(I) species (A). As noted above, Ar3Sb was
formed during the course of this reaction, however, the for-
mation of Ar3Sb was not detected by GC analysis of the reac-
tion mixture. This result would be explained that Ar3Sb is
easily oxidized to Ar3SbO or Ar3Sb(OAc)2 by air or excess
Cu(OAc)2 in the reaction mixture. A similar reaction was ob-
served in the N-arylation of amines23) and hydrazones25) by
use of Ar3Bi and Cu(OAc)2.
18) Jacobsen M. F., Knudsen M. M., Gothelf K. V., J. Org. Chem., 71,
9183—9190 (2006).
19) Zhang Z., Yu Y., Libeskind L. S., Org. Lett., 10, 3005—3008 (2008).
20) Lam P. Y. S., Deudon S., Averill K. M., Li R., He M. Y., Deshong P.,
Clark P., J. Am. Chem. Soc., 122, 7600—7601 (2000).
21) Lam P. Y. S., Vincent G., Bonne D., Clark C. G., Tetrahedron Lett., 43,
3091—3094 (2002).
22) Barton D. H. R., Donnelly D. M. X., Finet J.-P., Guiry P. J., J. Chem.
Soc., Perkin Trans. I, 1991, 2095—2102 (1991).
23) Barton D. H. R., Finet J.-P., Khamsi J., Tetrahedron Lett., 28, 887—
890 (1987).
24) Arnauld T., Barton D. H. R., Doris E., Tetrahedron, 53, 4137—4144
(1997).
25) Starkov P., Zemskov I., Sillard R., Ts˘ubrik O., Mäeorg U., Tetrahedron
Lett., 48, 1155—1157 (2007).
26) Kakusawa N., Tobiyasu Y., Yasuike S., Yamaguchi K., Seki H., Kurita
J., J. Organomet. Chem., 691, 2953—2968 (2006).
27) Kakusawa N., Kurita J., Chem. Pharm. Bull., 56, 1502—1504 (2008).
28) Qin W., Yasuike S., Kakusawa N., Sugawara Y., Kawahata M., Yama-
guchi K., Kurita J., J. Organomet. Chem., 693, 109—116 (2008).
29) Stolyarova T. E., Shavyrin A. S., Federov A. Y., Russ. Chem. Bull. Int.
Ed., 52, 1736—1739 (2003).
30) Dodonov V. A., Gushchin A. V., Tolstova O. G., Organomet. Chem.
U.S.S.R., 5, 274—277 (1992).
31) Yamamoto H., Oshima K., “Main Group Metals in Organic Synthesis,”
Wiley-VCH, Weinheim, 2004.
32) Akiba K.-y., “Chemistry of Hypervalent Compounds,” Wiley-VCH,
New York, 1999.
33) Typical procedure: To a solution of 2 (0.75 mmol), 6a (0.5 mmol), and
TEA (3.0 mmol) in CH2Cl2 (5 ml) was added Cu(OAc)2 (0.55 mmol),
and the mixture was stirred for 6 h at 40 °C (bath temperature). The
mixture was diluted with CH2Cl2 (50 ml) and NH3 aq. (1.5 mol/l,
50 ml) and then stirred for 30 min. The organic layer was separated,
washed with brine and dried over anhydrous MgSO4. After removal of
the solvent in vacuo, the residue was separated by SiO2 column chro-
matography (hexane : CH2Cl2ꢂ3 : 1) to give 7a (77 mg, 84% yield).
34) The tetraarylantimony acetates (2, 10, 11) were prepared by dis-
proportination reaction on heating 1 : 1 mixture of Ar5Sb and
Ar3Sb(OAc)2 in toluene (100 °C) for 3—6 h. 2: (C6H5)4SbOAc, mp
135—136 °C (lit.37) 129—131 °C), 10: (4-CH3C6H4)4SbOAc, mp
160—163 °C (lit.38) 157—158.1 °C), 11: (4-ClC6H4)4SbOAc, mp
184—187 °C.
In conclusion, we disclosed that hypervalent Ar4SbOAc is
a new N-arylating agent which can be used under mild condi-
tions without special care of exogenous oxygen. We have
also recently found that a similar N-arylation took place
when a mixture of Ar3Sb and amine (6) was heated with
large excess (2.5—5 eq) of Cu(OAc)2 in acetonitrile, how-
ever, the reaction requires a longer reaction time (6—24 h) at
higher temperature (60—70 °C). The details including its re-
action mechanism and further application of this simple and
mild N-arylation will be discussed in due course.
Acknowledgements This work was supported by a Grants-in-Aid for
Scientific Research (C) from Japan Society for the Promotion of Science
(JK), The “Academic Frontier” Project for Private Universities from the
Ministry of Education, Culture, Sports, Science and Technology of Japan
(WQ and SY), and Specific Research Fund of Hokuriku University (NK).
References and Notes
35) Lu W., Xi C., Tetrahedron Lett., 49, 4011—4015 (2008).
36) Lockhart T. P., J. Am. Chem. Soc., 105, 1940—1946 (1983).
37) Goel R. G., Can. J. Chem., 47, 4607—4612 (1969).
38) Affsprung H. E., Gainer A. B., Anal. Chim. Acta, 27, 578—584
(1962).
1) Ma D., Xia C., Jiang J., Zhang J., Tang W., J. Org. Chem., 68, 442—
451 (2003).
2) Ghosh A., Sieser J. E., Caron S., Couturier M., Dupont-Gaudet K., Gi-
rardin M., J. Org. Chem., 71, 1258—1261 (2006).
3) Hartwig J. F., Angew. Chem. Int. Ed., 37, 2046—2067 (1998).
4) Yang B. H., Buchwald S. L., J. Organomet. Chem., 576, 125—126