(d) E. J. Nunez and A. M. Echavarren, Chem. Rev., 2008, 108,
3326; (e) A. Furstner, Chem. Soc. Rev., 2009, 38, 3208.
5 (a) N. D. Shapiro and F. D. Toste, J. Am. Chem. Soc., 2007, 129,
4160; (b) G. Li and L. Zhang, Angew. Chem., Int. Ed., 2007, 46,
5156.
6 (a) L. Cui, Y. Peng and L. Zhang, J. Am. Chem. Soc., 2009, 131,
8394; (b) L. Cui, G. Zhang, Y. Pen and L. Zhang, Org. Lett., 2009,
11, 1225.
Scheme 2 Use of an ynol ether in the gold-catalysed oxidation
7 (a) H.-S. Yeom, J.-E. Lee and S. Shin, Angew. Chem., Int. Ed.,
2008, 47, 7040; (b) H.-S. Yeom, Y. Lee, J.-E. Lee and S. Shin,
Org. Biomol. Chem., 2009, 7, 4744.
reactions.
8 (a) During the course of our study Zhang and co-workers reported
the intermolecular oxidation of terminal alkynes to access and
employ monosubstituted a-oxo gold carbenoids, L. Ye, L. Cui,
G. Zhang and L. Zhang, J. Am. Chem. Soc., 2010, 132, 3258; also:
(b) L. Ye, W. He and L. Zhang, J. Am. Chem. Soc., 2010, 132,
8550; (c) For an intermolecular study of alkyne oxyarylation, see:
A. B. Cuenca, S. Montserrat, K. M. Hossain, G. Mancha,
A. Lledos, M. Medio-Simon, G. Ujaque and G. Asensio, Org.
Lett., 2009, 11, 4906.
9 Recent reviews of ynamide reactivity: (a) K. A. DeKorver, H. Li,
A. G. Lohse, R. Hayashi, Z. Lu, Y. Zhang and R. P. Hsung, Chem.
Rev., 2010, DOI: 10.1021/cr100003s; (b) G. Evano, A. Coste and
K. Jouvin, Angew. Chem., Int. Ed., 2010, 49, 2840.
Scheme 3 The oxidation/1,2-insertion reaction of chiral ynamides.
10 (a) F. Marion, J. Coulomb, C. Courillon, L. Fensterbank and
M. Malacria, Org. Lett., 2004, 6, 1509; (b) F. Marion, J. Coulomb,
A. Servais, C. Courillon, L. Fensterbank and M. Malacria,
Tetrahedron, 2006, 62, 3856; (c) E. Soriano and J. Marco-
Contelles, J. Org. Chem., 2005, 70, 9345; (d) Y. Zhang,
R. P. Hsung, X. Zhang, J. Huang, B. W. Slater and A. Davis,
Org. Lett., 2005, 7, 1047; (e) A. Buzas and F. Gagosz, Org. Lett.,
2006, 8, 515; (f) A. Buzas, F. Istrate and F. Gagosz, Tetrahedron,
2009, 65, 1889; (g) A. S. K. Hashmi, R. Salathie and W. Frey,
Synlett, 2007, 1763; (h) F. M. Istrate, A. K. Buzas, I. D. Jurberg,
Y. Odabachian and F. Gagosz, Org. Lett., 2008, 10, 925;
(i) G.-Y. Lin, C.-W. Li, S.-H. Hung and R.-S. Liu, Org. Lett.,
2008, 10, 5059; (j) S. Couty, C. Meyer and J. Cossy, Tetrahedron,
2009, 65, 1809; (k) A. S. K. Hashmi, M. Rudolph, J. W. Bats,
W. Frey, F. Rominger and T. Oeser, Chem.–Eur. J., 2008, 14,
6672; (l) S. Couty, C. Meyer and J. Cossy, Angew. Chem., Int.
Ed., 2006, 45, 6726; (m) S. Kramer, K. Dooleweerdt,
A. T. Lindhardt, M. Rottlander and T. Skrydstrup, Org. Lett.,
2009, 11, 4208.
highly substituted ynamide 8b, employed in the reaction as a
1 : 1 mixture of diastereomers, diverged significantly with
choice of reaction conditions.
Whilst the use of moderately elevated temperature and Au-I
(system A) afforded (E)-9b as the major isomer, a result
consistent with those observed in Table 1, the room temperature
reaction using AuBr3 in THF (system B) afforded (Z)-9b as the
major product. This stereoselective access to either geometric
isomer of chiral b-methoxy unsaturated carboxylic imides
from a mixture of diastereomers, could be of significant utility
in synthesis.z
In summary, we have demonstrated the gold-catalysed
site-specific intermolecular oxidation of ynamides and ynol
ethers. This method provides a means to access a-imido and
a-ester metal carbenoid reactivity from these electron-rich
p-systems. A general and efficient preparation of synthetically
important a,b-unsaturated carboxylic ester and imide derivatives,
as well as vinylogous carbimates is achieved from readily-
accessible materials. The mild reaction conditions are tolerant
of a wide range of functional groups, including other alkyne
moieties. The general potential of this approach for diazo-free
reaction development, as well as the specific synthetic utility of
the reactions detailed herein, are under study in our lab.
We thank the University of Birmingham for financial
support and Johnson Matthey plc for a generous loan of
metal salts. The work was part supported through Science
City Advanced Materials project 2, funded by AWM and
the ERDF.
11 Capture of in situ generated gold carbenoids using sulfoxides:
C. A. Witham, P. Mauleon, N. D. Shapiro, B. D. Sherry and
F. D. Toste, J. Am. Chem. Soc., 2007, 129, 5838.
12 (a) S. Couty, C. Meyer and J. Cossy, Synlett, 2007, 2819;
(b) Z. F. Al-Rashid and R. P. Hsung, Org. Lett., 2008, 10, 661.
13 Z. F. Al-Rashid, W. L. Johnson, R. P. Hsung, Y. Wei, P.-Y. Yao,
R. Liu and K. Zhao, J. Org. Chem., 2008, 73, 8780.
14 J. M. Concellon, H. Rodrıguez-Solla and P. Dıaz, J. Org. Chem.,
2007, 72, 7974 and references therein.
15 [2+2] cycloaddition/reversion with ynamides and carbonyl
moieties to prepare a,b-unsaturated carboxylic imides:
(a) R. P. Hsung, C. A. Zificsak, L.-L. Wei, C. J. Douglas,
H. Xiong and J. A. Mulder, Org. Lett., 1999, 1, 1237; (b) K. C.
M. Kurtz, R. P. Hsung and Y. Zhang, Org. Lett., 2006, 8, 231;
(c) L. You, Z. F. Al-Rashid, R. Figueroa, S. K. Ghosh, G. Li,
T. Lu and R. P. Hsung, Synlett, 2007, 1656; (d) N. Shindoh,
Y. Takemoto and K. Takasu, Chem.–Eur. J., 2009, 15, 7026.
16 Recent advances in ynamide synthesis: see ref. 9 and (a) Y. Zhang,
R. P. Hsung, M. R. Tracey, K. C. M. Kurtz and E. L. Vera, Org.
Lett., 2004, 6, 1151; (b) A. Coste, G. Karthikeyan, F. Couty and
G. Evano, Angew. Chem., Int. Ed., 2009, 48, 4381; (c) T. Hamada,
X. Ye and S. S. Stahl, J. Am. Chem. Soc., 2008, 130, 833 and
references therein.
Notes and references
1 (a) Carbene Chemistry, ed. G. Bertrand, Fontis Media, Lausanne,
Switzerland, 2002; (b) M. P. Doyle, M. A. McKervey and T. Ye,
Modern Catalytic Methods for Organic Synthesis with Diazo
Compounds, Wiley-Interscience, New York, 1998.
2 (a) G. Maas, Angew. Chem., Int. Ed., 2009, 48, 8186; (b) M. Regitz
and G. Maas, Diazo Compounds—Properties and Synthesis,
Academic Press, Orlando, 1986.
3 P. W. Davies and S. J. C. Albrecht, Angew. Chem., Int. Ed., 2009,
48, 8372.
4 Reviews: (a) A. Furstner and P. W. Davies, Angew. Chem., Int. Ed.,
2007, 46, 3410; (b) A. S. K. Hashmi, Chem. Rev., 2007, 107, 3180;
(c) D. J. Gorin and F. D. Toste, Nature, 2007, 446, 395;
17 A. S. K. Hashmi, J. P. Weyrauch, M. Rudolph and E. Kurpejovic,
Angew. Chem., Int. Ed., 2004, 43, 6545.
18 Examples of ynol ethers in gold catalysis (a) L. Zhang and
S. A. Kozmin, J. Am. Chem. Soc., 2004, 126, 11806;
(b) D. A. Engel and G. B. Dudley, Org. Lett., 2006, 8, 4027;
(c) A. S. K. Hashmi, M. Rudolph, J. Huck, W. Frey, J. W. Bats
and M. Hamzic, Angew. Chem., Int. Ed., 2009, 48, 5848.
19 Rhodium-catalysed diazodecomposition: D. F. Taber, R. J. Herr,
S. K. Pack and J. M. Geremia, J. Org. Chem., 1996, 61, 2908.
c
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Chem. Commun., 2011, 47, 379–381 381