140
S. Doran et al. / Journal of Organometallic Chemistry 717 (2012) 135e140
CH2Cl2). IR (KBr): ymax: 2944 (large), 1588, 1471, 1037 cmꢀ1 1H NMR
(400 MHz, CDCl3):
References
d
7.84 (d, J ¼ 8.1 Hz, 2H), 7.22 (d, J ¼ 7.9 Hz, 2H),
[1] (a) A. Börner (Ed.), Phosphorous Ligands in Asymmetric Catalysis, vol. IeIII,
Wiley-WCH, Weinheim, 2008;
5.40e5.25 (m, 2H), 4.20e4.02 (m, 2H), 2.51e2.40 (m, 1H), 2.37 (s,
3H), 2.40e2.26 (m, 4H), 2.19e1.88 (m, 3H), 1.34 (d, J ¼ 13.2 Hz, 9H),
(b) T.C. Nugent, M. El-Shazly, Adv. Synth. Catal. 352 (2010) 753;
(c) J. Xie, S. Zhu, Q. Zhou, Chem. Rev. 111 (2011) 1713;
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(b) A. Grabulosa, P-Stereogenic Ligands in Asymmetric Catalysis, RSC
Publishing, Cambridge, 2011.
0.92 (d, J ¼ 13.3 Hz, 9H) ppm. 13C NMR (400 MHz, CDCl3):
d 151.70
(s, C), 139.58 (s, C), 128.71 (s, CH), 124.62 (s, CH), 99.82 (d, J ¼ 8.1 Hz,
CH), 96.01 (s, CH), 67.67 (d, J ¼ 14.7 Hz, CH), 61.51 (d, J ¼ 15.6 Hz,
CH), 40.75 (d, J ¼ 22.3 Hz, C), 37.22 (dd, J ¼ 17.4, 3.8 Hz, C), 33.64 (s,
CH2), 33.27 (s, CH2), 29.48 (d, J ¼ 5.4 Hz, CH3 X 3), 28.51 (d,
J ¼ 5.6 Hz, CH3 X 3), 27.82 (s, CH2), 27.49 (s, CH2), 21.31 (s, CH3) ppm.
[3] (a) H. Hoge, H. Wu, W.S. Kissel, D.A. Pflum, D.J. Greene, J. Bao, J. Am. Chem. Soc.
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(b) G. Hoge, H. Wu, Org. Lett. 6 (2004) 3645;
(c) I.D. Gridnev, T. Imamoto, G. Hoge, M. Kouchi, H. Takahashi, J. Am. Chem.
Soc. 130 (2008) 2560.
31P NMR (300 MHz, CDCl3):
701 [(PNSO)Rh(PNSO)]þ.
d
148.74 (d, J ¼ 149.4 Hz) ppm. MS ESI:
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X. Verdaguer, Angew. Chem. Int. Ed. 49 (2010) 9452;
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M.A. Cortés, B. Colás, A. Riera, ChemBioChem 12 (2011) 625;
(c) T. León, A. Riera, X. Verdaguer, J. Am. Chem. Soc. 133 (2011) 5740.
[5] For other ligands with 3-hindred quadrant architecture, see: (a) W. Tang,
A.G. Capacci, A. White, S. Ma, S. Rodriguez, B. Qu, J. Savoie, N.D. Patel, X. Wei,
N. Haddad, N. Grinberg, N.K. Yee, D. Krishnamurthy, C.H. Senanayake, Org.
Lett. 12 (2010) 1104;
3.6. [Rh(PNSO)(COD)][BF4] (9)
The complex 8 (0.042g, 0.078mmol)was stirredinanhydrous Et2O
(3 mL) under N2 and HBF4$OEt2 (0.11 mL of a 1:10, HBF4$OEt2:Et2O
solution, 0.078 mmol) was then added A yellow precipitate quickly
formed and fell out of solution. This precipitate was washed several
times with anhydrous Et2O to yield pure product in quantitative yield
(b) K. Huang, X. Zhang, T.J. Emge, G. Hou, B. Cao, X. Zhang, Chem. Commun. 46
(2010) 8555.
(0.051 g, 99%). [
a
]D ¼ þ55.6 (c 0.85, CH2Cl2). IR (KBr): ymax 3506, 3199,
[6] The synthesis of the TCFP ligand was uncomplicated but not without draw-
backs as it involves a racemic procedure followed by separation of enantio-
mers by chiral preparative HPLC, which could be considered disadvantageous
on a larger scale. For other preparations of TCFP relying on asymmetric
synthesis, see: (a) T. Imamoto, K. Tamura, T. Ogura, Y. Ikematsu, D. Mayama,
M. Sugiya, Tetrahedron: Asymmetry 21 (2010) 1522;
(b) J. Granander, F. Secci, S.J. Canipa, P. O’Brien, B.J. Kelly, Org. Chem. 76 (2011)
4794.
[7] (a) J. Solà, M. Revés, A. Riera, X. Verdaguer, Angew. Chem. Int. Ed. 46 (2007)
5020;
2940 (broad), 1482, 1051 cmꢀ1 1H NMR (400 MHz, CDCl3):
d
8.19 (d,
J ¼ 8.2 Hz, 2H), 7.43 (d, J ¼ 8.0 Hz, 2H), 5.57e5.47 (m, 1H), 5.34e5.23
(m, 1H), 4.25 (d, J ¼ 49.5 Hz, 2H), 2.64e2.47 (m, 4H), 2.46 (s, 3H),
2.28e2.03 (m, 4H), 1.56 (d, J ¼ 14.6 Hz, 9H), 0.90 (d, J ¼ 15.0 Hz, 9H)
ppm. 13C NMR (400 MHz, CDCl3):
d 143.96 (s, C), 130.00 (s, CH), 125.10
(s, CH), 109.98 (s, C), 105.87 (s, CH), 100.54 (dd, J ¼ 12.0, 7.3 Hz, CH),
73.82 (s, CH), 64.58 (s, CH), 38.10 (s, C) 34.26 (s, CH2), 32.12 (s, CH2),
29.50 (d, J ¼ 5.9 Hz, CH3 X 3), 28.35 (s, CH2), 27.77 (d, J ¼ 6.1 Hz, CH3 X
3), 26.71 (s, CH2), 21.60 (s, CH3) ppm. 31P NMR (300 MHz, CDCl3):
(b) M. Revés, T. Achard, J. Solà, A. Riera, X. Verdaguer, J. Org. Chem. 73 (2008)
7080;
(c) Y. Ji, A. Riera, X. Verdaguer, Org. Lett. 11 (2009) 4346;
(d) A. Vázquez-Romero, J. Rodríguez, A. Lledó, X. Verdaguer, A. Riera, Org. Lett.
10 (2008) 4509.
d
140.11 (d, J ¼ 150.2 Hz) ppm. MS ESI: 701 [(PNSO)Rh(PNSO)]þ.
[8] For the use of sulfinamides in synthesis and catalysis, see: (a) M.T. Robak,
M.A. Herbage, J.A. Ellman, Chem. Rev. 110 (2010) 3600;
(b) D.A. Cogan, G. Liu, K. Kim, B.J. Backes, J.A. Ellman, J. Am. Chem. Soc. 120
(1998) 8011;
(c) I. Fernandez, N. Khiar, Chem. Rev. 103 (2003) 3651;
(d) Y. Zhang, S. Chitale, N. Goyal, G. Li, Z.S. Han, S. Shen, S. Ma, N. Grinberg,
H. Lee, B.Z. Lu, C.H. Senanayake, J. Org. Chem. 77 (2012) 690.
[9] (a) T. Achard, J. Benet-Buchholz, A. Riera, X. Verdaguer, Organometallics 28
(2009) 480;
(b) T. Achard, J. Benet-Buchholz, E.C. Escudero-Adán, A. Riera, X. Verdaguer,
Organometallics 30 (2011) 3119.
[10] To work as a three-hindered quadrant ligand, 2 should work preferentially as
a P, S ligand. For the successful use of P, S ligands in asymmetric hydroge-
nation see: D.A. Evans, F.E. Michael, J.S. Tedrow, K.R. Campos, J. Am. Chem. Soc.
125 (2003) 3534.
3.7. General procedure for hydrogenations
A glass sample tube fitted with a stirring bar was loaded with
the MAC substrate and the catalyst (5 mol %). The sample tube was
placed in a pressure vessel. In open air, anhydrous degassed MeOH
was added to the sample tube to a substrate concentration of
0.228 ꢂ 10ꢀ3 M. The reaction vessel was sealed tightly and, with the
aid of vacuum, purged with nitrogen. The vessel was then con-
nected to a hydrogen gas manifold where with the aid of vacuum
was filled with hydrogen at the designated pressure. The closed
vessel was left to stir for 24 h. Then, the pressure was released from
the vessel and the reaction mixture was diluted EtOAc and filtered
through a short pad of silica. The solvent was removed in vacuo to
yield an off-white solid. HPLC: CHIRALPAK AD-H, 90% Heptane-10%
[11] Structurally related neutral Rh complexes have been reported, see: (a)
K.A. Chatziapostolou, K.A. Vallianatou, A. Grigoropoulos, C.P. Raptopoulou,
A. Terzis, I.D. Kostas, P. Kyritsis, G.J. Pneumatikakis, J. Organomet. Chem. 692
(2007) 4129;
(b) A.M.Z. Slawin, M.B. Smith, J.D. Woollins, J. Chem. Soc. Dalton Trans. (1996)
4575.
IPA, 1 mL/min,
l
¼ 220 nm, tR isomer ¼ 8.8, tS isomer ¼ 12.3 min.
[12] Monochelated cationic complex 6, previously reported by our group,
provides full conversion to the hydrogenated compound with 0% enantio-
meric excess (5 mol% of 6, CH2Cl2, 20 bar of H2, rt, 22 h). The corresponding
bis-chelated complex 7 fails to provide the hydrogenation product under the
same reaction conditions.
[13] The quadrant analysis method was initially proposed by Knowles for C2
symmetric diphosphines, see: W.S. Knowles, Acc. Chem. Res. 16 (1983)
106 For examples of three-hindered quadrant phosphines see Refs. [3]
and [5].
Acknowledgments
We thank the MEC (CTQ2011-23620), Generalitat de Catalunya
(2009SGR-00901) and Enantia S. L. for financial support. S.D. Thanks
“La Caixa” Foundation for a fellowship.
[14] It is also possible that the S-coordinated complex is not the most abun-
dant but rather the most active in the hydrogenation process that results
in the formation of the R enantiomer of 11. The results obtained with
higher hydrogen pressure are in concordance with this assumption. By
enhancing the hydrogen pressure, the most abundant less reactive O-
coordinated complex may become reactive inducing erosion of the
enantioselectivity.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in