COMMUNICATIONS
6954; f) D. S. Surry, S. L. Buchwald, Chem. Sci. 2010, 1,
13; g) I. P. Beletskaya, A. Cheprakov, Coord. Chem.
Rev. 2004, 248, 2337–2364; h) D. Ma, Y. Jiang, Chimia
2011, 65, 914–918; i) G. E. Job, S. L. Buchwald, Org.
Lett. 2002, 4, 3703–3706; j) J. W. Grate, G. C. Frye, in:
Sensors Update, Vol. 2, (Eds.: H. Baltes, W. Gçpel, J.
Hesse), Wiley-VCH, Weinheim, 1996, pp 10–20; k) C.
Sambiagio, S. P. Marsden, A. J. Blacker, P. C. McGo-
wan, Chem. Soc. Rev. 2014, 43, 3525–3550; l) V. MagnØ,
T. Garnier, M. Danel, P. Pale, S. Chassaing, Org. Lett.
2015, 17, 4494–4497.
[9] For NHC as Pd or Ni ligands in cross-coupling reac-
tions, see below and references cited therein; a) A.
À
À
Chartoire, S. P. Nolan, Advances in C C and C -X cou-
pling using palladium-N-heterocyclic carbene (Pd-
NHC) complexes, in: RSC Catalysis Series, 2015, 21
(New Trends in Cross-Coupling), pp 139–227; b) M.
Henrion, V. Ritleng, M. J. Chetcuti, ACS Catal. 2015, 5,
1283–1302; c) D. Colosimo, M. Dominguez, G. Rowe,
Synthesis of palladium(II)-NHC compounds and their
employment as cross-coupling catalysts, in: Abstracts of
Papers, 249th ACS National Meeting & Exposition,
Denver, CO, USA, March 22–26, 2015, INOR-268.
[10] The potential of NHCs as Ullmann ligands was re-
vealed in recent publications that described the NMR
mechanistic studies of trifuoromethylation using pre-
formed (IPr)Cu-CF3 complex. See G. G. Dubinina, H.
Furutachi, D. A. Vicic, J. Am. Chem. Soc. 2008, 130,
8600–8601; G. G. Dubinina, J. Ogikubo, D. A. Vicic,
Organometallics 2008, 27, 6233–6235.
[3] The classic Ullmann coupling reaction was documented
as early as 1901, see: F. Ullmann, J. Bielecki, Ber.
Dtsch. Chem. Ges. 1901, 34, 2174–2185; P. E. Fanta,
Synthesis 1974, 9–21.
[4] Per info from InfoMine.com, price ratio of Pd/Cu in
January 2015 was ~4000.
[5] The EMEA option 1 limits for palladium and copper
are 10 ppm and 250 ppm, respectively, for a daily dose
of less than 10 grams. See: Guideline on the Specifica-
tion Limits for Residues of Metal Catalysts or Metal Re-
[6] a) R. K. Gujadhur, C. G. Bates, D. Venkataraman, Org.
Lett. 2001, 3, 4315; b) M. Wolter, G. Nordmann, G. E.
Job, S. L. Buchwald, Org. Lett. 2002, 4, 973.
[11] Preformed trinuclear copper(I) complexes with triscar-
bene ligands were reported to catalyze Ullman-type ar-
ylations of azoles and phenols. These catalysts require
special preparation, are limited in reaction scope, and
therefore may have limited potential for synthetic ap-
plications. See: A. Biffis, C. Tubaro, E. Scattolin, M.
Basato, G. Papini, C. Santini, E. Eleuterio Alvarezc, S.
Conejero, Dalton Trans. 2009, 7223–7229.
[12] A. Abeywardane, M. Burke, S. Kapadia, T. Kirrane, M.
Netherton, H. Razavi;. S. Rodrigues, A. Saha, L. Smith
Keenan, H. Takahashi, M. Turner, J.-P. Wu, E. Young,
Q. Zhang, R. Zindell, Benzodioxane Inhibitors of Leu-
kotriene Production, WO Patent WO 2013134226, 2013.
[13] S. P. Nolan, in: N-Heterocyclic Carbenes: Effective
Tools for Organometallic Synthesis, 1st edn., Wiley-
VCH, Weinheim, 2014.
[7] With CuI/1,10-phenanthroline as the catalyst, as much
as 15% chiral erosion at C-2 was observed when the
solvent volume (toluene) was less than 20 L/kilogram
of substrate. The reaction volume must be maintained
at or above 20 LkgÀ1 in order to reduce racemization
to the acceptable level of less than 2–3% chiral ero-
sion.
[8] a) S. Díez-Gonzµlez, S. P. Nolan, Aldrichimica Acta
2008, 41, 43–51; b) N. Germain, M. Magrez, S. Kehrli,
M. Mauduit, A. Alexakis, Eur. J. Org. Chem. 2012,
5301–5306; c) M. Yoshida, H. Ohmiya, M. Sawamura,
J. Am. Chem. Soc. 2012, 134, 11896–11899.
Adv. Synth. Catal. 2016, 358, 1924 – 1928
1928
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim