Job/Unit: O21601
/KAP1
Date: 14-01-13 16:50:28
Pages: 6
J. E. Glover, D. J. Martin, P. G. Plieger, G. J. Rowlands
SHORT COMMUNICATION
X-ray Crystallography: The X-ray data were recorded at low tem-
perature with a Rigaku-Spider X-ray diffractometer comprising a
Rigaku MM007 microfocus copper rotating-anode generator, high-
flux Osmic monochromating and focusing multilayer mirror optics
(Cu-Kα radiation, λ = 1.5418 Å) and a curved image-plate detector.
CrystalClear[17] was utilised for data collection and FSProcess in
PROCESS-AUTO[18] for cell refinement and data reduction. The
structure of 11b was solved by direct methods and expanded by
Fourier techniques.[19] Non-hydrogen atoms were refined anisotrop-
ically. Hydrogen atoms were placed in calculated positions and re-
pling a range of bulky and electron-rich substrates. It can
be used to prepare a number of tri-ortho-substituted biaryls
which will be necessary for future studies into atroposelec-
tive couplings. The di-tert-butylphoshane 12 showed high
activity, giving the best results for the coupling of aryl
chlorides, but struggled with more sterically demanding
coupling partners. We believe that the dicyclohexyl-
phosphane shows the most promise, presumably as its
bulky, electron-rich nature is tempered by a degree of flexi-
bility, and future studies on asymmetric couplings will focus fined by using a riding model with fixed isotropic U values.
on this ligand.
Crystal Data for Dicyclohexyl[1-([2.2]paracyclophan-4-yl)-4-pentyl-
1H-1,2,3-triazol-5-yl]phosphane Oxide (11b): C35H48N3OP, Mr
=
557.73, translucent plate, 0.20ϫ0.20ϫ0.20 mm, monoclinic,
P21/n, a = 9.2860(9), b = 17.3451(12), c = 19.1655(17) Å, α = β =
γ = 90(1)°, U = 3086.9(5) Å3, Z = 4, μ = 1.021 mm–1, F(000) =
1208, T = 143(2) K. A total of 26656 reflections were collected in
the range 6.60° Ͻ 2θ Ͻ 58.9°. The 4348 independent reflections
Conclusions
The first planar chiral [2.2]paracyclophane-derived 1,4-
disubstituted 1,2,3-triazoles have been readily prepared
from 4-azido[2.2]paracyclophane. The triazoles can be se-
lectively functionalised to give monophosphanes. The na-
ture of the C-4 substituent of the triazole has a profound
effect on the stability of the new phosphanes. The phos-
phanes show promise in palladium-mediated coupling reac-
tions, overcoming the limitations of our original planar chi-
ral imidazoles, and their application in atroposelective cou-
pling reactions will be explored. Additionally, a new route
to 4-amino[2.2]paracyclophane has been uncovered. The
full scope and limitations of this amination methodology
will be delineated and reported in due course.
[R(int) = 0.079] were used after absorption correction (Tmax
=
0.822). The refinement of 362 parameters converged to R1 = 0.1273
[for 2474 reflections having IϾ2σ(I)], wR2 = 0.3638, goodness-of-
fit is 1.21 (for all 4348 F2 data), peak/hole ratio: 0.58/–0.81 eÅ–3.
Supporting Information (see footnote on the first page of this arti-
cle): 1H, 13C and 31P NMR spectra and more detailed results of
the Suzuki–Miyaura reaction.
Acknowledgments
We thank Massey University for financial support (to G. J. R.) and
a University Technicians Award (J. E. G.). We thank KISCO Ltd.
for the donation of [2.2]paracyclophane.
Experimental Section
[1] a) A. Börner, Phosphorus Ligands in Asymmetric Catalysis:
Synthesis and Applications, Wiley, Chichester, UK, 2008, p.
1546; b) U. Christmann, R. Vilar, Angew. Chem. 2005, 117,
370; Angew. Chem. Int. Ed. 2005, 44, 366–374; c) A. Zapf, M.
Beller, Chem. Commun. 2005, 431–440; d) M. Miura, Angew.
Chem. 2004, 116, 2251; Angew. Chem. Int. Ed. 2004, 43, 2201–
2203.
[2] a) D. S. Surry, S. L. Buchwald, Angew. Chem. 2008, 120, 6438;
Angew. Chem. Int. Ed. 2008, 47, 6338–6361; b) R. Martin, S. L.
Buchwald, Acc. Chem. Res. 2008, 41, 1461–1473.
[3] a) A. S. K. Hashmi, Angew. Chem. 2010, 122, 5360; Angew.
Chem. Int. Ed. 2010, 49, 5232–5241; b) P. K. Dhondi, P. Car-
berry, L. B. Choi, J. D. Chisholm, J. Org. Chem. 2007, 72,
9590–9596; c) M. Movassaghi, M. D. Hill, J. Am. Chem. Soc.
2006, 128, 14254–14255; d) J. Haider, K. Kunz, U. Scholz, Adv.
Synth. Catal. 2004, 346, 717–722.
[4] a) S. Harkal, F. Rataboul, A. Zapf, C. Fuhrmann, T. Riermeier,
A. Monsees, M. Beller, Adv. Synth. Catal. 2004, 346, 1742–
1748; b) T. Schulz, C. Torborg, S. Enthaler, B. Schaffner, A.
Dumrath, A. Spannenberg, H. Neumann, A. Borner, M. Beller,
Chem. Eur. J. 2009, 15, 4528–4533; c) T. Schulz, C. Torborg,
B. Schaffner, J. Huang, A. Zapf, R. Kadyrov, A. Borner, M.
Beller, Angew. Chem. 2009, 121, 936; Angew. Chem. Int. Ed.
2009, 48, 918–921; d) C. Torborg, J. Huang, T. Schulz, B.
Schaffner, A. Zapf, A. Spannenberg, A. Borner, M. Beller,
Chem. Eur. J. 2009, 15, 1329–1336; e) A. Sergeev, G. T. Schulz,
C. Torborg, A. Spannenberg, H. Neumann, M. Beller, Angew.
Chem. 2009, 121, 7731; Angew. Chem. Int. Ed. 2009, 48, 7595–
7599.
Preparation of 1-([2.2]Paracyclophan-4-yl)-4-pentyl-1H-1,2,3-tri-
azole (8) as a Representative Procedure: A suspension of 4-
azido[2.2]paracyclophane (6; 6.0 g, 24.1 mmol, 1.0 equiv.), CuI
(9.2 g, 48.1 mmol, 2.0 equiv.), sodium ascorbate (2.38 g, 12.0 mmol,
0.5 equiv.), Bu4NBr (3.87 g, 12.0 mmol, 0.5 equiv.) in Et3N
(20.1 mL, 144.4 mmol, 6.0 equiv.) and CH2Cl2/H2O (1:1, 240 mL)
was degassed by bubbling N2 through the solution. Hept-1-yne
(4.7 mL, 36.1 mmol, 1.5 equiv.) was added and the suspension
heated at 80 °C overnight. The suspension was cooled to room
temp., EtOAc (150 mL) was added and the layers separated. The
aqueous layer was extracted with EtOAc (150 mL) and the organic
layers were filtered and washed with satd. aq. NH4Cl followed by
H2O (2ϫ 100 mL). The organic phase was dried (MgSO4), concen-
trated and the residue purified by column chromatography (5%
EtOAc/hexane to 10% EtOAc/hexane). Triazole 8 was isolated as
a white solid (6.75 g, 81%).
Preparation of 5-(Dicyclohexylphosphanyl)-1-([2.2]paracyclophan-4-
yl)-4-pentyl-1H-1,2,3-triazole (11) as a Representative Procedure:
nBuLi (2.5 m in hexanes; 1.4 mL, 3.5 mmol, 1.2 equiv.) was added
dropwise to a solution of triazole 8 (1.0 g, 2.9 mmol, 1.0 equiv.)
in THF (30 mL) at 0 °C. The red solution was stirred for 15 min
whereupon Cy2PCl (0.8 mL, 3.5 mmol, 1.2 equiv.) was added. The
solution was stirred at room temp. for 2 h and then poured into
satd. aq. NH4Cl (50 mL). The layers were separated and the aque-
ous phase extracted with EtOAc (2ϫ 50 mL). The combined or-
ganic layers were washed with brine (100 mL), dried (MgSO4) and
concentrated. The orange residue was purified by column
chromatography (5% EtOAc/hexanes) to give 11 as a white solid
(0.9 g, 55%).
[5] a) W. K. Chow, O. Y. Yuen, C. M. So, W. T. Wong, F. Y.
Kwong, J. Org. Chem. 2012, 77, 3543–3548; b) C. M. So, C. P.
Lau, A. S. C. Chan, F. Y. Kwong, J. Org. Chem. 2008, 73, 7731–
7734; c) C. M. So, C. P. Lau, F. Y. Kwong, Org. Lett. 2007, 9,
4
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0