Angewandte
Chemie
Tol), 128.9 (s, o-Tol) 130.0 (s, p-NHC), 135.0 (o-NHC), 136.3 (ipso-
C6H5), 136.7 (p-Tol), 138.8 (ipso-Tol), 146.9 (ipso-NHC), 152.2
(triazolide-C), 154.6 (triazolide-C), 204.7 ppm (N2CCu). MS (+p
ESI): m/z (%) = 792.406 (100.00) [M+(63Cu)+H], 793.411 (45.50)
[M+(63Cu)+2H]. IR: n˜ = 3057 (w), 2962 (s), 2924 (s), 2868 (m), 2097
(w), 1602 (w), 1513 (m), 1481 (m), 1459 (s), 1428 (s), 1385 (m), 1364
(w), 1327 (m), 1274 (s), 1182 (m), 1058 (w), 988 (m), 805 (s), 788 (m),
770 (s), 758 cmÀ1 (s). M.p. 2358C (decomp). Elemental analysis (%)
calcd for C50H58CuN5: C 75.77, H 7.38, N 8.84; found: C 75.24, H 7.33,
N 8.73. CCDC-625315 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
ac.uk/data_request/cif.
Porco, Jr., Tetrahedron 2006, 62, 6405; b) B. H. M. Kuijpers,
G. C. T. Dijkmans, S. Groothuys, P. J. L. M. Quaedflieg, R. H.
Blaauw, F. L. van Delft, F. P. J. T. Rutjes, Synlett 2005, 3059; c) J.
Deng, Y.-M. Wu, Q.-Y. Chen, Synthesis 2005, 2730.
[9] a) B. F. Straub, P. Hofmann, Angew. Chem. 2001, 113, 1328;
Angew. Chem. Int. Ed. 2001, 40, 1288; b) B. F. Straub, F.
Rominger, P. Hofmann, Organometallics 2000, 19, 4305;
c) B. F. Straub, I. Gruber, F. Rominger, P. Hofmann, J. Organo-
met. Chem. 2003, 684, 124; d) B. F. Straub, Angew. Chem. 2005,
117, 6129; Angew. Chem. Int. Ed. 2005, 44, 5974.
[10] L. A. Goj, E. D. Blue, C. Munro-Leighton, J. L. Petersen, T. B.
Gunnoe, Inorg. Chem. 2005, 44, 8647.
[11] a) N. P. Mankad, T. G. Gray, D. S. Laitar, J. P. Sadighi, Organo-
metallics 2004, 23, 1191; b) A. J. Arduengo III, R. Krafzyk, R.
Schmutzler, H. A. Craig, J. R. Goerlich, W. J. Marshall, M.
Unverzagt, Tetrahedron 1999, 55, 14523; c) G. A. Grasa, M. S.
Viciu, J. Huang, S. P. Nolan, J. Org. Chem. 2001, 66, 7729; d) L.
Jafarpour, E. D. Stevens, S. P. Nolan, J. Organomet. Chem. 2000,
606, 49.
[12] S. D. Dꢀez-Gonzꢁles, A. Correa, L. Cavallo, S. P. Nolan, Chem.
Eur. J. 2006, 12, 7558.
[13] Cross experiments are in progress to rule out fast, reversible
NHC dissociation, acetylide ligand exchange, and formation of
dinuclear complexes.
[14] With a p-acceptor ligand instead of a strong donor ligand, such
as an N-heterocyclic carbene, a coordination number of 3 at a 16-
valence-electron copper complex would certainly be a viable
alternative for intermediates in click catalysis.
[15] a) M. John, C. Auel, C. Behrens, M. Marsch, K. Harms, F.
Bosold, R. M. Gschwind, P. R. Rajamohanan, G. Boche, Chem.
Eur. J. 2000, 6, 3060; b) G. Boche, F. Bosold, M. Marsch, K.
Harms, Angew. Chem. 1998, 110, 1779; Angew. Chem. Int. Ed.
1998, 37, 1684.
[16] a) SIR97: A. Altomare, M. C. Burla, M. Camalli, G. L. Cascar-
ano, C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G.
Polidori, R. Spagna, J. Appl. Crystallogr. 1999, 32, 115;
b) SHELXL-97 (G. M. Sheldrick, University of Gꢂttingen, 97-
2 version).
Received: October 30, 2006
Revised: January 3, 2007
Published online: February 15, 2007
Keywords: alkynes · azides · click chemistry · copper ·
.
cycloadditions · reaction mechanisms
[1] A. Michael, J. Prakt. Chem. 1893, 48, 94.
[2] R. Huisgen, Angew. Chem. 1963, 75, 604.
[3] a) V. V. Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless,
Angew. Chem. 2002, 114, 2708; Angew. Chem. Int. Ed. 2002, 41,
2596; b) C. W. Tornøe, C. Christensen, M. Meldal, J. Org. Chem.
2002, 67, 3057.
[4] K. B. Sharpless, M. G. Finn, Angew. Chem. 2001, 113, 11, 2056;
Angew. Chem. Int. Ed. 2001, 40, 2004.
[5] a) W. Kirmse, L. Horner, Justus Liebigs Ann. Chem. 1958, 614, 1;
b) L. D. Pachon, J. H. van Maarseveen, G. Rothenberg, Adv.
Synth. Catal. 2005, 347, 811.
[6] V. D. Bock, H. Hiemstra, J. H. van Maarseveen, Eur. J. Org.
Chem. 2006, 51.
[7] a) F. Himo, T. Lovell, R. Hilgraf, V. V. Rostovtsev, L. Noodle-
man, K. B. Sharpless, V. V. Fokin, J. Am. Chem. Soc. 2005, 127,
210; b) V. O. Rodionov, V. V. Fokin, M. G. Finn, Angew. Chem.
2005, 117, 2250; Angew. Chem. Int. Ed. 2005, 44, 2210.
[8] For trapping of assumed copper(I) triazolide intermediates by
electrophiles, see a) B. Gerard, J. Ryan, A. B. Beeler, J. A.
[17] a) Ortep-3 for Windows: L. J. Farrugia, J. Appl. Crystallogr.
Angew. Chem. Int. Ed. 2007, 46, 2101 –2103
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2103