Journal of the American Chemical Society
Article
(6) (a) Rosewall, C. F.; Sibbald, P. A.; Liskin, D. V.; Michael, F. E. J.
Am. Chem. Soc. 2009, 131, 9488. (b) Sibbald, P. A.; Rosewall, C. F.;
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(7) Leading references for 1,2-amino-arylation and -vinylation
reactions: (a) Ney, J. E.; Wolfe, J. P. Angew. Chem., Int. Ed. 2004,
43, 3605. (b) Ney, J. E.; Wolfe, J. P. J. Am. Chem. Soc. 2005, 127, 8644.
(c) Bertrand, M. B.; Neukom, J. D.; Wolfe, J. P. J. Org. Chem. 2008, 73,
8851. (d) Mai, D. N.; Wolfe, J. P. J. Am. Chem. Soc. 2010, 132, 12157.
(e) Babij, N. R.; McKenna, G. M.; Forwald, R. M.; Wolfe, J. P. Org.
Lett. 2014, 16, 3412. (f) Hopkins, B. A.; Wolfe, J. P. Chem. Sci. 2014, 5,
4840 and references cited therein.. See also: (g) Hayashi, S.;
Yorimitsu, H.; Oshima, K. Angew. Chem., Int. Ed. 2009, 48, 7224.
(h) Bagnoli, L.; Cacchi, S.; Fabrizi, G.; Goggiomani, A.; Scarponi, C.;
Tiecco, M. J. Org. Chem. 2010, 75, 2134.
(8) 1,2-Aminoalkynylation reactions: (a) Nicolai, S.; Waser, J. Org.
Lett. 2011, 13, 6324. (b) Nicolai, S.; Piemontesi, C.; Waser, J. Angew.
Chem., Int. Ed. 2011, 50, 4680. (c) Nicolai, S.; Sedigh-Zadeh, R.;
Waser, J. J. Org. Chem. 2013, 78, 3783.
(9) For a similar, but mechanistically distinct approach to alkene 1,2-
aminoallylation, see: Hewitt, J. F. M.; Williams, L.; Aggarwal, P.; Smith,
C. D.; France, D. J. Chem. Sci. 2013, 4, 3538.
(10) Reference 7f outlines specific limitations of the alkene
component that are relevant to Approach B in Scheme 1.
(11) An additional benefit of this approach resides in the synthetic
flexibility of the imine moiety of the product.
(12) (a) Tsutsui, H.; Narasaka, K. Chem. Lett. 1999, 28, 45.
(b) Tsutsui, H.; Kitamura, M.; Narasaka, K. Bull. Chem. Soc. Jpn. 2002,
75, 1451. For reviews, see: (c) Kitamura, M.; Narasaka, K. Chem. Rec.
2002, 2, 268. (d) Narasaka, K.; Kitamura, M. Eur. J. Org. Chem. 2005,
4505.
reduction from the less hindered face of the imine accounts for
the observed diastereoselectivities.
CONCLUSIONS
■
The present study outlines an umpolung approach to alkene
carboamination enabled by oxidative addition of Pd(0)-
catalysts into the N−O bond of oxime esters. This provides a
unified strategy for a wide range of amino-functionalizations, as
highlighted by prototypical methods for 1,2-amino-acylation,
-carboxylation, -arylation, -vinylation, and -alkynylation. For
carbonylative processes, orchestrated protodecarboxylation of
the pentafluorobenzoate leaving group is crucial for efficient
cyclization. This process is likely a key feature in related
Narasaka−Heck cyclizations, and the studies here provide
important insights into the efficacy of O-pentafluorobenzoyl
oxime esters in aza-Heck reactions of this type. Compared to
established 1,2-carboamination methods, other notable features
of the present approach include a tolerance to sterically
demanding 1,1-disubstituted alkenes and the synthetic options
provided by the imine moiety of the products. Consequently,
this strategy may provide a valuable counterpoint to existing
carboamination approaches. Future studies will align the
development of enantioselective variants with more efficient
protocols and stereocontrolled manipulations of the cyclization
products. We are also developing related carboamination
processes that employ other electrophilic nitrogen sources.
ASSOCIATED CONTENT
* Supporting Information
■
(13) Imino-Pd(II) complexes formed via this process have been
characterized by X-ray diffraction. For example, see: Tan, Y.; Hartwig,
J. F. J. Am. Chem. Soc. 2010, 132, 3676.
S
Experimental details and characterization data. The Supporting
(14) This initiation mode has been used to achieve alkene 1,2-
carboamination but only in the context of fully intramolecular Heck-
type cascades: (a) Kitamura, M.; Zaman, S.; Narasaka, K. Synlett 2001,
974. (b) Zaman, S.; Kitamura, M.; Narasaka, K. Bull. Chem. Soc. Jpn.
2003, 76, 1055. (c) For a recently reported 1,2-iodoamination
protocol that is postulated to proceed via an imino-Pd intermediate,
see: Chen, C.; Hou, L.; Cheng, M.; Su, J.; Tong, X. Angew. Chem., Int.
Ed. 2015, 54, 3092.
AUTHOR INFORMATION
Corresponding Author
■
Notes
(15) (a) Faulkner, A.; Bower, J. F. Angew. Chem., Int. Ed. 2012, 51,
1675. (b) Race, N. J.; Bower, J. F. Org. Lett. 2013, 15, 4616.
(c) Faulkner, A.; Scott, J. S.; Bower, J. F. Chem. Commun. 2013, 49,
1521. For a copper-catalyzed variant, see: (d) Faulkner, A.; Race, N.
J.; Bower, J. F. Chem. Sci. 2014, 5, 2416.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
A.F. thanks AstraZeneca and the University of Bristol for a
Ph.D. studentship. EPSRC (EP/J007455/1) is thanked for
support. J.F.B. is indebted to the Royal Society for a University
Research Fellowship.
(16) Nishimura, T.; Nishiguchi, Y.; Maeda, Y.; Uemura, S. J. Org.
Chem. 2004, 69, 5342.
(17) This protodecarboxylation pathway is particularly facile for
trialkylammonium pentafluorobenzoates. Ammonium benzoate de-
rivatives do not undergo significant protodecarboxylation under the
reaction conditions.
(18) Previous approaches to alkene 1,2-aminoacylation (see reference
5) exploit Friedel-Crafts-type acylation of Ar−H bonds and this limits
the range of R-groups that can be introduced. For a process that
employs organometallic nucleophiles but is stoichiometric in
palladium, see: Ambrosini, L. M.; Cernak, T. A.; Lambert, T. H.
Synthesis 2010, 870.
(19) For example, use of PhSnBu3 (110 mol%) as the nucleophile
delivered 10a in approximately 30% yield. However, addition of LiCl
(100 mol%) resulted in trace quantities (<10%) of 10a.
(20) For discussions on transmetalation from organoboron
derivatives in the context of the Suzuki coupling, see: (a) Lennox,
A. J. J.; Lloyd-Jones, G. C. Chem. Soc. Rev. 2014, 43, 412. (b) Lennox,
A. J. J.; Lloyd-Jones, G. C. Angew. Chem., Int. Ed. 2013, 52, 7362. For
the nucleophilicities of a series of furyl boronic acid derivatives, see:
(c) Berionni, G.; Maji, B.; Knochel, P.; Mayr, H. Chem. Sci. 2012, 3,
878. For the synthesis and reactivity of tetraarylborates, see: (d) Lu,
REFERENCES
■
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