Organic Letters
Letter
On the other hand, this asymmetric hydrosilylation reaction
could also be performed using a different strategy with a chiral
auxiliary (Scheme 3c). By exploiting our Si−O coupling reaction
established earlier in this work, we were able to produce chiral
silane intermediates 17 in situ from a range of chiral alcohol
auxiliaries 16. Chiral intermediates 17 could then be used to
hydrosilylate acetophenone in the same catalytic reaction system.
Subsequent Si−O cleavage of 18 with TBAF afforded 1-
phenylethanol (15) in good yields and moderate to good
enantioselectivity, depending on the chiral auxiliary used
(5) Gao, D.; Cui, C. Chem. - Eur. J. 2013, 19, 11143.
6) Selected examples: (a) Miller, R. L.; Maifeld, S. V.; Lee, D. Org. Lett.
004, 6, 2773. (b) Mirza-Aghayan, M.; Boukherroub, R.; Bolourtchian,
M. J. Organomet. Chem. 2005, 690, 2372. (c) Rendler, S.; Auer, G.;
Oestreich, M. Angew. Chem., Int. Ed. 2005, 44, 7620. (d) Mukherjee, D.;
Thompson, R. R.; Ellern, A.; Sadow, A. D. ACS Catal. 2011, 1, 698.
(
2
(
e) Weickgenannt, A.; Mohr, J.; Oestreich, M. Tetrahedron 2012, 68,
3
468. (f) Fukumoto, K.; Kasa, M.; Nakazawa, H. Inorg. Chim. Acta 2015,
4
31, 219.
(7) Selected examples: (a) Tanino, K.; Yoshitani, N.; Moriyama, F.;
Kuwajima, I. J. Org. Chem. 1997, 62, 4206. (b) Le Bideau, F.; Coradin,
T.; Henique, J.; Samuel, E. Chem. Commun. 2001, 1408. (c) Grajewska,
A.; Oestreich, M. Synlett 2010, 2010, 2482. (d) Weickgenannt, A.;
Mewald, M.; Muesmann, T. W. T.; Oestreich, M. Angew. Chem., Int. Ed.
(
Scheme 3c). Cinchonine and cinchonidine gave almost
opposite stereoselective induction as expected.
In conclusion, we have established a novel method to use N-
heterocyclic olefins as efficient Brønsted base organocatalysts for
the direct dehydrogenative coupling reactions of hydrosilanes
and hydroxyl compounds. NHO catalysts can also trigger the
reductive hydrosilylation of unsaturated alcohols and carbonyl
compounds with excellent outcomes. In a preliminary study, we
were able to induce stereoselectivity for the hydrosilylation of a
ketone using chiral auxiliaries or a chiral NHO catalyst. This work
not only offered a convenient method for the synthesis of silyl
ethers but also advanced the synthetic utility of NHOs as a
versatile class of organocatalysts.
2
010, 49, 2223. (e) Weickgenannt, A.; Mewald, M.; Oestreich, M. Org.
Biomol. Chem. 2010, 8, 1497. (f) Kruger, A.; Albrecht, M. Chem. - Eur. J.
012, 18, 652. (g) Blandez, J. F.; Primo, A.; Asiri, A. M.; Alvaro, M.;
̈
2
Garcia, H. Angew. Chem., Int. Ed. 2014, 53, 12581. (h) Cardoso, J. M. S.;
Lopes, R.; Royo, B. J. Organomet. Chem. 2015, 775, 173. (i) Dhak-
shinamoorthy, A.; Concepcion, P.; Garcia, H. Chem. Commun. 2016, 52,
2725. (j) Vijjamarri, S.; Chidara, V. K.; Rousova, J.; Du, G. Catal. Sci.
Technol. 2016, 6, 3886.
(8) Weickgenannt, A.; Oestreich, M. Chem. - Asian J. 2009, 4, 406.
(
9) Toutov, A. A.; Betz, K. N.; Haibach, M. C.; Romine, A. M.; Grubbs,
R. H. Org. Lett. 2016, 18, 5776.
10) Selected reviews: (a) Ryan, S. J.; Candish, L.; Lupton, D. W.
(
Chem. Soc. Rev. 2013, 42, 4906. (b) Hopkinson, M. N.; Richter, C.;
Schedler, M.; Glorius, F. Nature 2014, 510, 485. (c) Flanigan, D. M.;
Romanov-Michailidis, F.; White, N. A.; Rovis, T. Chem. Rev. 2015, 115,
ASSOCIATED CONTENT
Supporting Information
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*
S
9
(
307.
11) Synthetic methodology: (a) Zhao, Q.; Curran, D. P.; Malacria, M.;
Fensterbank, L.; Goddard, J.-P.; Lacote, E. Chem. - Eur. J. 2011, 17, 9911.
Mechanistic studies: (b) Gatineau, D.; Zhao, Q.; Curran, D. P.; Malacria,
M.; Lacote, E.; Fensterbank, L.; Goddard, J.-P. Dalton Trans. 2013, 42,
7458.
Experimental details; analytical data; NMR spectra (PDF)
AUTHOR INFORMATION
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*
(
12) See review: He, L.; Guo, H.; Wang, Y.; Du, G.-F.; Dai, B.
Tetrahedron Lett. 2015, 56, 972.
13) (a) Blumel, M.; Crocker, R. D.; Harper, J. B.; Enders, D.; Nguyen,
T. V. Chem. Commun. 2016, 52, 7958. (b) Blumel, M.; Noy, J.-M.;
Enders, D.; Stenzel, M. H.; Nguyen, T. V. Org. Lett. 2016, 18, 2208.
14) (a) Recent literature on NHOs as organocatalysts: (a) Crocker, R.
ORCID
(
̈
Author Contributions
(
D.; Nguyen, T. V. Chem. - Eur. J. 2016, 22, 2208. (b) Wang, Y.-B.; Wang,
Y.-M.; Zhang, W.-Z.; Lu, X.-B. J. Am. Chem. Soc. 2013, 135, 11996.
(c) Naumann, S.; Thomas, A. W.; Dove, A. P. Angew. Chem., Int. Ed.
U.K. and U.P.N.T. contributed equally.
Notes
2
015, 54, 9550. (d) Wang, Y.-B.; Sun, D.-S.; Zhou, H.; Zhang, W.-Z.; Lu,
X.-B. Green Chem. 2015, 17, 4009. (e) Naumann, S.; Thomas, A. W.;
Dove, A. P. ACS Macro Lett. 2016, 5, 134. (f) Saptal, V. B.; Bhanage, B.
M. ChemSusChem 2016, 9, 1980. (g) Naumann, S.; Wang, D.
Macromolecules 2016, 49, 8869.
(15) Selected recent examples: (a) Weickgenannt, A.; Mewald, M.;
Muesmann, T. W. T.; Oestreich, M. Angew. Chem., Int. Ed. 2010, 49,
2223. (b) Rendler, S.; Plefka, O.; Karatas, B.; Auer, G.; Froehlich, R.;
Mueck-Lichtenfeld, C.; Grimme, S.; Oestreich, M. Chem. - Eur. J. 2008,
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
J.H. thanks A*STAR for support and NCI for computer time.
The project was supported by the Australian Research Council
Grant DE150100517 awarded to T.V.N. U.K. thanks the DAAD
and the ERC for funding the research exchange to UNSW.
1
(
4, 11512.
16) For example, see: Karatas, B.; Rendler, S.; Froehlich, R.;
REFERENCES
■
(
(
1) (a) Protection for the Hydroxyl Group. Greene’s Protective Groups
in Organic Synthesis, 5th ed.; Wuts, P. G. M., Ed. John Wiley & Sons, Inc.:
t
(18) Tertiary alcohols are not activated by NHOs; therefore, NaO Bu
can be used to deprotonate the NHO precursor in situ (see ref 13). This
feature can potentially be used in selective silylation of primary or
secondary alcohols in mixtures with tertiary alcohols.
2
014; pp 17−471. (b) Kocienski, P. J. Hydroxyl Protecting Groups,
Protecting Groups, 3rd ed.; Georg Thieme Verlag: 2003; pp 187−350.
2) (a) Pouget, E.; Tonnar, J.; Lucas, P.; Lacroix-Desmazes, P.;
Ganachaud, F.; Boutevin, B. Chem. Rev. 2010, 110, 1233. (b) Cheng, C.;
Watts, A.; Hillmyer, M. A.; Hartwig, J. F. Angew. Chem., Int. Ed. 2016, 55,
(
(
2
(
2
19) Levens, A.; An, F.; Breugst, M.; Mayr, H.; Lupton, D. W. Org. Lett.
016, 18, 3566.
20) Melaimi, M.; Soleilhavoup, M.; Bertrand, G. Angew. Chem., Int. Ed.
010, 49, 8810.
1
(
(
1872.
3) Lejars, M.; Margaillan, A.; Bressy, C. Chem. Rev. 2012, 112, 4347.
4) (a) Zou, H.; Wu, S. S.; Shen, J. Chem. Rev. 2008, 108, 3893.
b) Brook, M. A. Silicon in Organic, Organometallic, and Polymer
(21) Rendler, S.; Oestreich, M. Synthesis 2005, 2005, 1727.
(22) Tan, M.; Zhang, Y.; Ying, J. Y. Adv. Synth. Catal. 2009, 351, 1390.
(
Chemistry; Wiley: New York, 2000. (c) Xu, L.-W.; Chen, Y.; Lu, Y.
Angew. Chem., Int. Ed. 2015, 54, 9456.
D
Org. Lett. XXXX, XXX, XXX−XXX