Journal of the American Chemical Society
Page 4 of 5
1
2
3
4
5
6
7
8
9
(b) Negishi, E.; Williams, R. M.; Lew, G.; Yoshida, T. J. Organomet.
Scheme 5. Proposed mechanism for the formation of (Z)ꢀ
Chem. 1975, 92, C4. (c) Campbell, J. B. Jr.; Molander, G. A. J.
Organomet. Chem. 1978, 156, 71. (d) Matteson, D. S.; Majumdar, D.
Organometallics 1983, 2, 230. (e) Brown, H. C.; Srebnik, M.; Bhat, N.
G. Tetrahedron Lett. 1988, 29, 2635. (f) Gano, J. E.; Srebnik, M.
Tetrahedron Lett. 1993, 34, 4889. (g) Deloux, L.; Srebnik, M.; Bhat, N.
G. J. Org. Chem. 1994, 59, 6871. (h) Soderquist, J. A.; Rane, A. M.;
Matos, K.; Ramos, J. Tetrahedron Lett. 1995, 36, 6847. (i) Molander,
G. A.; Ellis, N. M. J. Org. Chem. 2008, 73, 6841.
vinylboronates with 2.
2
H
R
CH4
R
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
R
BPin
H
HBPin
H
(
CyAPDI)Co
(6) (a) Molybdenumꢀcatalyzed alkene cross metathesis has recently been
described as a direct route to (Z)ꢀvinylboronates although excess
vinylBPin and partial vacuum were required for high selectivity, see:
Kiesewetter, E. T.; O'Brien, R. V.; Yu, E. C.; Meek, S. J.; Schrock, R.
R.; Hoveyda, A. H. J. Am. Chem. Soc. 2013, 135, 6026. (b) A
palladiumꢀcatalyzed Zꢀselective hydroboration of an enyne, methylꢀ1ꢀ
butenꢀ3ꢀyne, using HBCat was reported, see: Xu, S.; Haeffner, F.; Li,
B.; Zakharov, L.; Liu, S. Angew. Chem. Int. Ed. 2014, 53, 6795.
(7) Ohmura, T.; Yamamoto, Y.; Miyaura, N. J. Am. Chem. Soc. 2000, 122,
4990.
H
R
(
CyAPDI)Co BPin
BPin
(
CyAPDI)Co
R
R
pro-E isomer
(
CyAPDI)Co
R
H
(8) Gunanathan, C.; Hölscher, M.; Pan, F.; Leitner, W. J. Am. Chem. Soc.
2012, 134, 14349.
BPin
(9) Sundararaju, B.; Fürstner, A. Angew. Chem. 2013, 125, 14300.
(10) [Fe]: (a) Wu, J. Y.; Moreau, B.; Ritter, T.; J. Am. Chem. Soc. 2009, 131,
12915. (b) Haberberger, M.; Enthaler, S. Chem. Asian. J. 2013, 8, 50.
(c) Obligacion, J. V.; Chirik, P. J. Org. Lett. 2013, 15, 2680. (d)
Greenhalgh, M. D.; Thomas, S. P. Chem. Commun. 2013, 49, 11230.
(e) Zheng, J. X.; Sortais, J. B.; Darcel, C. ChemCatChem. 2014, 6, 763.
(f) Rawat, V. S.; Sreedhar, B. Synlett 2014, 25, 1132. [Ni] (g)
Zaidlewicz, M.; Meller, J. Tetrahedron Lett. 1997, 38, 7279. (h) Ely, R.
J.; Morken, J. P. J. Am. Chem. Soc. 2010, 132, 2534. (i) Yu, Z.; Ely, R.
J.; Morken, J. P. Angew. Chem. Int. Ed. 2014, 53, 9632.
(11) Obligacion, J. V.; Chirik, P. J. J. Am. Chem. Soc. 2013, 51, 19107.
(12) (a) Zhang, L.; Zuo, Z. Q.; Leng, X. B.; Huang, Z. Angew. Chem. Int.
Ed. 2014, 53, 2696. (b) Ruddy, A. J.; Sydora, O. L.; Small, B. L.;
Stradiotto, M.; Turculet, L. Chem. Eur. J. 2014, 20, 13918.
(13) Palmer, W. N.; Diao, T.; Pappas, I.; Chirik, P. J. ACS Catal. 2015, 5,
622.
(14) Monfette, S.; Turner, Z. R.; Semproni, S. P.; Chirik, P. J. J. Am. Chem.
Soc. 2012, 134, 4561.
(15) (a) Zhang, L.; Zuo, Z.; Wan, X.; Huang, Z. J. Am. Chem. Soc. 2014,
136, 15501. (b) Chen, J.; Xi, T.; Ren, X.; Cheng, B.; Guo, J.; Zhan, L.
Org. Chem. Front. 2014, 20, 13918.
(16) (a) Gibson, V. C.; Humphries, M. J.; Tellmann, K. P.; Wass, D. F.;
White, A. J. P.; Williams, D. J. Chem. Commun. 2001, 2252. (b)
Knijnenburg, Q.; Horton, A. D.; van der Heijden, H.; Smits, J. M. M.;
de Bruin, B.; Budzelaar, P. H. M.; Gal, A. W. J. Mol. Catal. A: Chem.
2005, 232, 151ꢀ159.
(17) Atienza, C. C. H.; Diao, T. N.; Weller, K. J.; Nye, S. A.; Lewis, K. M.;
Delis, J. G. P.; Boyer, J. L.; Roy, A. K.; Chirik, P. J. J. Am. Chem. Soc.
2014, 136, 12108.
An additional stoichiometric experiment was performed to
support the mechanism in Scheme 5. Addition of PhC≡CBPin
to 2 in the presence of HBPin at 23 ºC furnished CH3BPin and
an 85:15 mixture of 5-Pro-(E) and 5-Pro-(Z), clearly
supporting the competency of alkynylboronates for
regioselective insertion into CoꢀH bonds as well as rapid
isomerization between cobalt vinyl compounds in the absence
of excess alkyne.
In summary, a cobalt catalyzed method for the synthesis of
(Z)ꢀvinylboronates
by
regioꢀ
and
strereoselective
hydroboration of terminal alkynes has been developed.
Isotopic labeling and stoichiometric studies eliminate the
possibility of metal vinylidene intermediates and support a
previously unconsidered
hydrometallation reactions.
pathway for
(Z)ꢀselective
Acknowledgment. We thank Princeton University for financial
support. JVO acknowledges the Paul Maeder ’75 Fund for Energy
and the Environment through the Andlinger Center for Energy and the
Environment. We also thank W. Neil Palmer for useful discussions
and Dr. Istvan Pelczer for assistance with NMR spectroscopy.
Supporting Information Available: Complete experimental details,
representative NMR spectra and crystallographic data for 2 and 5-
(Pro)-E in cif format. This material may be accessed, free of charge,
via the internet at http//:pubs.acs.org.
(18) Bowman, A. C.; Milsmann, C.; Bill, E.; Lobkovsky, E.; Weyhermüller,
T.; Wieghardt, Chirik, P. J. Inorg. Chem. 2010, 49, 6110.
(19) The lower Z:E selectivity results from slow catalyst initiation to form
compound 3 and generates a small amount of a CoꢀH leading to the the
(E) isomer. The position of the deuterium in the (E)ꢀvinylboronate
product implies that the (E) isomer resulted from a CoꢀH rather than the
isomerization of 5-Pro-(Z) to 5ꢀPro-(E).
References
(1) (a) Suzuki, A. Angew. Chem. Int. Ed. 2011, 50, 6722 (b) Suzuki, A. J.
Organomet. Chem. 1999, 576, 147. (c) Miyaura, N.; Suzuki, A.; Chem.
Rev. 1995, 95, 2457.
(2) (a) Cordova, A. Ed. Catalytic Asymmetric Conjugate Reactions; Wileyꢀ
VCH: Weinheim, 2010. (b) Mahrwald, R., Ed. Modern Aldol Reactions;
WileyꢀVCH: Weinheim, 2010.
(3) (a) Brown, H. C.; Gupta, S. K. J. Am. Chem. Soc. 1972, 94, 4370. (b)
Brown, H. C.; Gupta, S. K. J. Am. Chem. Soc. 1975, 97, 5249. (c)
Tucker, C. E.; Davidson, J.; Knochel, P. J. Org. Chem. 1992, 57, 3482.
(4) For Eꢀselective hydroboration of terminal alkynes (metalꢀcatalyzed):
[Rh]: (a) Pereira, S.; Srebnik, M. Tetrahedron Lett. 1996, 37, 3283. (b)
Lee, T.; Baik, C.; Jung, I.; Song, K.ꢀH., Kim, S.; Kim, D.; Kang, S.ꢀO.;
Ko, J. Organometallics 2004, 23, 4569. (c) Neilson, B. M.; Bielawski,
C. W. Organometallics 2013, 32, 3121. [Zr]: (d) Pereira, S.; Srebnik,
M. Organometallics 1995, 14, 3127. [Ti]: (e) He, X.; Hartwig, J. F. J.
Am. Chem. Soc. 1996, 118, 1696. (f) [Cu]: Semba, K.; Fujihara, T.;
Terao, J.; Tsuji, Y. Chem. Eur. J. 2012, 18, 4179.
(20) The 85:15 ratio was determined from the 1H NMR spectrum of the
benzeneꢀd6 solution of the isomers of 5. Upon quenching with DCl, the
(Z):(E) ratio of the resulting organic product was measured by GC (the
small GC response factor variations in the (Z) and (E) vinylboronates
were not corrected) to be 80:20. Analyzing the organic product by
quantitative 13C NMR spectroscopy revealed a 75:25 ratio. We believe
that this slight discrepancy in the isomeric ratio is not due to
isomerization but rather due to the use of different analytical methods to
determine the ratio.
(21) Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P. Organometallics 1990,
9, 3127.
(5) For synthesis of ZꢀalkenylꢀBR2 or ꢀB(OR)2 compounds (stoichiometric
methods): (a) Dieck, H. A.; Heck, R. F. J. Org. Chem. 1975, 40, 1083.
ACS Paragon Plus Environment