Organic Letters
Letter
43, 5976. (c) Ibuka, T.; Nakai, K.; Habashita, H.; Bessho, K.; Fujii, N.
Tetrahedron 1993, 49, 9479. (d) Ibuka, T.; Tanaka, M.; Nishii, S.;
Yamamoto, Y. J. Am. Chem. Soc. 1989, 111, 4864. (e) Gao, Y.; Sharpless,
K. B.J. Am.Chem. Soc.1988,110,7538.(f)Ibuka, T.;Nakao, T.;Nishii,S.;
Yamamoto, Y. J. Am. Chem. Soc. 1986, 108, 7420.
(7) (a) Sharma, P. K.; Romanczyk, L. J., Jr.; Kondaveti, L.; Reddy, B.;
Arumugasamy, J.; Lombardy, R.; Gou, Y.; Schroeter, H. Org. Lett. 2015,
17, 2306. (b) Bozell, J. J.; Miller, D.; Hames, B. R.; Loveless, C. J. Org.
Chem. 2001,66,3084. (c)Gao,Y.;Sharpless, K. B. J. Am. Chem. Soc.1988,
110, 7538.
coupling product with retention of the original configuration at
the benzylic carbon.
On the other hand, the presence of acid (HBF4 or Bu4NHSO4)
would give rise to the formation of a benzylic carbocation
intermediate.11 Direct addition of a potassium organotrifluor-
oborate from the least hindered face (Re face)20,21 would explain
the major formation of the diastereomer with inversion of the
original configuration at the benzylic carbon.22
In conclusion, we have developed for the first time the
transition metal-free, C(sp2)−C(sp3), diastereoselective cross
couplingbetweenunprotected syndiolsandalkenyl-, hetaryl-, and
arylboronic acids or potassium organotrifluoroborates. By using
boronic acids in the presence of TFAA, the reaction takes place
with retention of configuration, whereas the use of potassium
organotrifluoroborates and HBF4 favors formation ofthe reaction
products with inversion of configuration at the benzylic carbon.
Given that the starting syn diols are easily obtained in either
optically pure form by the Sharpless dihydroxylation of alkenes,
the method provides all four diastereomers of the coupling
products in a stereocomplementary approach.
(8)(a)Molander, G. A. J. Org. Chem. 2015, 80, 7837. (b)Hall, D. G., Ed.
Boronic Acids: Preparation and Applications in Organic Synthesis, Medicine
and Materials; Wiley-VCH: Weinheim, 2011.
(9) Berionni, G.; Maji, B.; Knochel, P.; Mayr, H. Chem. Sci. 2012, 3, 878.
(10) Roscales, S.; Csaky, A. G. Chem. Soc. Rev. 2014, 43, 8215.
́
̈
́
(11) (a) For reactions with epoxides, see: Roscales, S.; Csaky, A. G.
̈
Chem. Commun. 2014, 50, 454. (b) For reactions with cyclopropanes,
see: Ortega, V.; Csaky, A. G. J. Org. Chem. 2016, 81, 3917. (c) Nguyen, T.
́
̈
N.; Nguyen, T. S.; May, J. A. Org. Lett. 2016, 18, 3786. (d) For non-
diastereoselective reactions with secondary benzylic halides and
mesylates, see: Li, C.; Zhang, Y.; Sun, Q.; Gu, T.; Peng, H.; Tang, W. J.
Am. Chem. Soc. 2016, 138, 10774. (e) For non-stereoselective reactions
with benzydryl alcohols, see: Fisher, K. M.; Bolshan, Y. J. Org. Chem.
2015, 80, 12676. (f) For non-stereoselective reactions with allylic
alcohols, see: Li, X. − D.; Xie, L. − J.; Kong, D. − L.; Liu, L.; Cheng, L.
Tetrahedron 2016, 72, 1873−1880.
ASSOCIATED CONTENT
* Supporting Information
■
S
TheSupportingInformationisavailablefreeofchargeontheACS
(12) See, for example: (a) Shen, T.; Zhang, Y.; Liang, Y.-F.; Jiao, N. J.
Am. Chem. Soc. 2016, 138, 13147. (b) Palmieri, A.; Petrini, M. Org.
Biomol. Chem. 2012, 10,3486. (c)Garden, S.J.;daSilva,R.B.;Pinto, A.C.
Tetrahedron 2002, 58, 8399 and references cited therein.
Fullexperimentaldetails, synthesisofthestartingmaterials,
characterization data, and copies of NMR spectra (PDF)
(13)Obtainedbydihydroxylationofthecorresponding(E)-alkenewith
(15)Obtainedbydihydroxylationofthecorresponding(E)-alkenewith
(16) Bergman, J.; Lidgren, J. Tetrahedron Lett. 1989, 30, 4597.
(17) See, for example: (a) Huang, K.; Sheng, G.; Lu, P.; Wang, Y. Org.
Lett. 2017, 19, 4114. (b) Liu, H.; Jiang, G.; Pan, X.; Wan, X.; Lai, Y.; Ma,
D.; Xie, W. Org. Lett. 2014, 16, 1908. (c) Han, L.; Liu, C.; Zhang, W.; Shi,
X.-X.; You, S.-L. Chem. Commun. 2014, 50, 1231.
(18) See, for example: (a) Molinaro, C.; Scott, J. P.; Shevlin, M.; Wise,
C.; Menard, A.; Gibb, A.; Junker, E. M.; Lieberman, D. J. Am. Chem. Soc.
́
AUTHOR INFORMATION
■
Corresponding Author
ORCID
́
Notes
The authors declare no competing financial interest.
2015,137,999.(b)Chen, G.;Shigenari,T.;Jain, P.;Zhang, Z.;Jin,Z.;He,
J.; Li, S.; Mapelli, C.; Miller, M. M.; Poss, M. A.; Scola, P. M.; Yeung, K. −
S.; Yu, J. Q. J. Am. Chem. Soc. 2015, 137, 3338. (c) He, F. S.; Jin, J. − H.;
Yang, Z. −T.;Yu, X.; Fossey, J. S.;Deng, W. −P. ACSCatal. 2016, 6, 652.
(d) Zheng, B. H.; Ding, C. − H.; Hou, X. − L.; Dai, L. X. Org. Lett. 2010,
12, 1688.
(19) (a) Al-Zoubi, R. M.; Marion, O.; Hall, D. G. Angew. Chem., Int. Ed.
2008, 47, 2876. (b) Arnold, K.; Davies, B.; Giles, R. L.; Grosjean, C.;
Smith, G. E.; Whiting, A. Adv. Synth. Catal. 2006, 348, 813.
(20) Bachs model for the reaction of chiral benzylic cations. See:
(a) Stadler, D.; Bach, T. Chem. - Asian J. 2008, 3, 272. (b) Wilcke, D.;
Bach, T. Org. Biomol. Chem. 2012, 10, 6498 See also:. (c) Bozell, J. J.;
Miller, D.; Hames, B. R.; Loveless, C. J. Org. Chem. 2001, 66, 3084.
(21) Trifluoroborates are nucleophilic enough to transfer their organic
backbone to electrophilic centers directly without the need of
coordination. See, for example: Lee, S.; MacMillan, D. W. C. J. Am.
Chem. Soc. 2007, 129, 15438. See also ref 11.
(22) Although oxonium stabilization of the benzylic carbocation
intermediate is possible, we have previously demonstrated (ref 11a) that
epoxides react with organotrifluoroboronic acids under TFAA
promotion via formation of a B-unsaturated RBF2 species, following a
borderline SNi mechanism with inversion of the configuration. Reaction
via the epoxide would require coordination of an unsaturated boron
species to the oxygen of the epoxide. This is unlikely to happen under the
present reaction conditions (RBF3K, HBF4, or Bu4NHSO4).
ACKNOWLEDGMENTS
This work was supported by project CTQ2014-52213-R from the
Spanish government (MICINN).
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REFERENCES
■
(1) See, for example: Jozwiak, K., Lough, W. J., Wainer, I. W., Eds. Drug
Stereochemistry: Analytical Methods and Pharmacology, 3rd ed.; Informa:
New York, 2012.
(2) See, for example: Singh, K.; Shakya, P.; Kumar, A.; Alok, S.; Kamal,
M.; Singh, S. P. Int. J. Pharm. Sci. Res. 2014, 5, 4644.
(3) See, for example: (a) Bihani, M.; Zhao, J. C.-G. Adv. Synth. Catal.
2017, 359, 534. (b) Oliveira, M. T.; Luparia, M.; Audisio, D.; Maulide, N.
Angew. Chem., Int. Ed. 2013, 52, 13149. (c) Oliveira, M. T.; Audisio, D.;
Niyomchon, S.; Maulide, N. ChemCatChem 2013, 5, 1239. (d) Jacobsen,
E. N., Pfaltz, A., Yamamoto, H., Eds. Comprehensive Asymmetric Catalysis;
Springer: New York, 1999; Vols. I−III, Suppl. I−II. (e) Luparia, M.;
́
Oliveira, M. T.; Audisio, D.; Frebault, F.; Goddard, R.; Maulide, N.
Angew. Chem., Int. Ed. 2011, 50, 12631. (f) Krautwald, S.; Sarlah, D.;
Schafroth, M. A.; Carreira, E. M. Science 2013, 340, 1065.
(4) Carreira, E. M.; Kvaerno, L. Classics in Stereoselective Synthesis;
Wiley: Weinheim, 2009.
(5) Johnson, R. A., Sharpless, K. B. In Catalytic Asymmetric Synthesis,
2nd ed.; Ojima, I., Ed.; Wiley-VCH: Weinheim, 2000, Chapter 6A, p 357.
(6) (a) Bozell, J. J.; Miller, D.; Hames, B. R.; Loveless, C. J. Org. Chem.
2001, 66, 3084. (b) Katz, J. E.; Dumlao, D. S.; Wasserman, J. I.;
Lansdown, M. G.; Jung, M. E.; Faull, K. F.; Clarke, S. Biochemistry 2004,
D
Org. Lett. XXXX, XXX, XXX−XXX