COMMUNICATIONS
Easily Accessible TADDOL-Derived Bisphosphonite Ligands
Pꢄmies, C. Claver, Tetrahedron: Asymmetry 2004, 15,
2113–2122; d) C. Claver, M. Diꢃguez, O. Pꢄmies, S.
Castillꢅn, Top. Organomet. Chem. 2006, 18, 35–64; e) J.
Klosin, C. R. Landis, Acc. Chem. Res. 2007, 40, 1251–
1259; f) S. H. Chikkali, J. I. van der Vlugt, J. N. H.
Reek, Coord. Chem. Rev. 2014, 262, 1–15.
tential has been proven in the asymmetric hydrofor-
mylation of different vinylarenes where high reaction
rates, moderate to good regio- and very good enantio-
selectivities were achieved. In addition, through bene-
fits such as the ease of preparation, the stability to-
wards air and moisture and the possibility to include
structural diversity, these ligands should prove valua-
ble for asymmetric catalysis.
[3] a) C. Botteghi, S. Paganelli, A. Schionato, M. Marche-
tti, Chirality 1991, 3, 355–369; b) S. Ho, C. Bucher, J. L.
Leighton, Angew. Chem. Int. Ed. 2013, 52, 6757–6761;
c) R. M. Risi, S. D. Burke, Org. Lett. 2012, 14, 1180–
1182; d) R. M. Risi, S. D. Burke, Org. Lett. 2012, 14,
2572–2575; e) B. Breit, A. Bigot, Chem. Commun.
2008, 6498–6500.
Experimental Section
[4] N. Sakai, S. Mano, K. Nozaki, H. Takaya, J. Am. Chem.
Typical Procedure for the Asymmetric
Hydroformylation of Styrene
Soc. 1993, 115, 7033–7034.
[5] a) Y. J. Yan, X. M. Zhang, J. Am. Chem. Soc. 2006, 128,
7198–7202; b) X. W. Zhang, B. N. Cao, Y. J. Yan, S. C.
Yu, B. M. Ji, X. M. Zhang, Chem. Eur. J. 2010, 16, 871–
877.
[6] G. M. Noonan, C. J. Cobley, T. Mahoney, M. L. Clarke,
Chem. Commun. 2014, 50, 1475–1477.
To a dried Schlenk flask 11a (14.0 mg, 14.0 mmol, 1 mol%)
was added and [Rh(cod)OMe]2 (339 mg, 1.40 mmol,
0.05 mol%) was added as a THF stock solution (prepared
immediately before use), further THF was added to adjust
the total volume to 0.7 mL. The reaction mixture was trans-
ferred into a steel autoclave via syringe under an argon at-
mosphere and purged 4 times with 5 bar of CO/H2 (1:1), fol-
lowed by adjustment of the reaction pressure to 20 bar.
After 2 h at 458C, the mixture was cooled to room tempera-
ture, carefully depressurized and styrene (15a) (160 mL,
1.40 mmol) was added in THF (0.3 mL). The autoclave was
again purged and pressurized as before and the reaction was
stirred magnetically for 24 h under 20 bar and at 458C. Sub-
sequently the autoclave was cooled to room temperature,
vented, the mixture was filtered through a plug of silica gel
with Et2O and analyzed by GC.
[7] M. Dieguez, O. Pamies, A. Ruiz, S. Castillon, C.
Claver, Chem. Commun. 2000, 1607–1608.
[8] a) T. P. Clark, C. R. Landis, S. L. Freed, J. Klosin, K. A.
Abboud, J. Am. Chem. Soc. 2005, 127, 5040–5042;
b) A. L. Watkins, B. G. Hashiguchi, C. R. Landis, Org.
Lett. 2008, 10, 4553–4556.
[9] D. Seebach, A. K. Beck, A. Heckel, Angew. Chem.
2001, 113, 96–142; Angew. Chem. Int. Ed. 2001, 40, 92–
138.
[10] Prof. Xia (Lanzhou) and Prof. Ding (Shanghai) report-
ed on a structurally related bisphosphonate ligand. In-
troducing chiral diphenols as chiral modulator, also
highly active but less enantioselective catalysts have
been developed: B. Zhao, X. Peng, Z. Wang, C. Xia, K.
Ding, Chem. Eur. J. 2008, 14, 7847–7857.
Acknowledgements
[11] Prof. Reek (Amsterdam) and Prof. Schmalz (Cologne)
designed TADDOL-based hybrid phosphine/phosphites
and phosphine/phosphoramidites, showing good activity
and moderate to good selectivity: a) T. Robert, Z.
Abiri, J. Wassenaar, A. J. Sandee, S. Romanski, J. M.
Neudçrfl, H. G. Schmalz, J. N. H. Reek, Organometal-
lics 2010, 29, 478–483; b) J. Wassenaar, B. de Bruin,
J. N. H. Reek, Organometallics 2010, 29, 2767–2776.
[12] Rh(nbd)2]BF4 is better known as a precursor for hydro-
genation reactions. Nevertheless, under Syngas pressure
this precursor is converted to the neutral hydride com-
plex as well, the actual HF catalyst. During this process
two equivalents norbornane and one equivalent HBF4
are generated as side products. Due to the presence of
this acid, the enantioselectivity is most likely to be de-
graded by acid-catalyzed racemization.
This work was supported by the DFG, the International Re-
search Training Group “Catalysts and Catalytic Reactions for
Organic Synthesis” (IRTG 1038) and the Krupp Foundation.
We thank Umicore, BASF and Wacker for generous gifts of
chemicals.
References
[1] For reviews on hydroformylation see: a) Rhodium Cat-
alyzed Hydroformylation, Vol. 22, (Eds.: P. W. N. M.
Van Leeuwen, C. Claver), Kluwer Academic Publish-
ers, Dordrecht, 2000; b) B. Breit, W. Seiche, Synthesis
2001, 1–36; c) B. Breit, Angew. Chem. 2005, 117, 6976–
6986; Angew. Chem. Int. Ed. 2005, 44, 6816–6825; d) R.
Franke, D. Selent, A. Bçrner, Chem. Rev. 2012, 112,
5675–5732.
[13] Purifying the aldehyde via chromatography caused a de-
terioration of the optical purity (65% ee).
[14] The [a]D of the isolated acids indicated that virtually
no racemization occurred during oxidation.
[15] Exclusively the (S)-enantiomer of Naproxen is actually
approved as a drug. Employing the opposite enantio-
mer of ligand 11a will provide the correct configura-
tion.
[2] For reviews on AHF see: a) F. Agbossou, J. F. Carpent-
ier, A. Mortreaux, Chem. Rev. 1995, 95, 2485–2506;
b) C. Claver, P. W. N. M. Van Leeuwen, in: Rhodium
Catalyzed Hydroformylation, Vol. 22, (Eds.: P. W. N. M.
Van Leeuwen, C. Claver), Kluwer Academic Publish-
ers, Dordrecht, 2000, pp 107–124; c) M. Diꢃguez, O.
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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