ORGANIC
LETTERS
2007
Vol. 9, No. 21
4395-4397
Activation of Carbon
Palladium: Toward a Mild, Catalytic
Approach to -Amino Acid Derivatives
−Oxygen Bonds by
r
Yingdong Lu and Bruce A. Arndtsen*
Department of Chemistry, McGill UniVersity, 801 Sherbrooke Street West,
Montreal, Quebec H3A 2K6, Canada
Received August 27, 2007
ABSTRACT
A Lewis acid mediated method to induce the carbon
The product of this reaction has been crystallographically characterized. This reaction suggests the potential use of such ethers as an alternative
to organic halides in palladium catalyzed carbon carbon bond formation. As an illustration of this potential, this reaction has been used to
design a mild, catalytic route to -amino acid derivatives from
−oxygen bond of amide-substituted ethers to undergo addition to palladium is described.
−
r
r-phenoxyamides and carbon monoxide.
The transition-metal-based cleavage of covalent bonds (e.g.,
by oxidative addition) is a central transformation in orga-
nometallic chemistry and metal catalysis. In palladium
catalysis alone, this reaction is involved in Heck couplings,
allylations, cross-coupling chemistry (e.g., Stille, Suzuki,
Hiyama, Sonogashira couplings), reductions, and many other
important reactions.1,2 In general, the substrates employed
in catalytic reactions involving oxidative addition to pal-
ladium contain either highly polarized R-X bonds (e.g.,
organic halides, triflates, iodonium salts, esters) or relatively
weak or accessible bonds.3 Conversely, the use of the less
polarized and stable carbon-oxygen bonds of ethers in such
bond activation processes is more limited.4,5 While allylic
and propargylic ethers have been employed in palladium
catalysis,4b,6 examples of ethers in such reactions usually
involve compounds with strain (e.g., epoxides)7 or require
the in situ conversion of the ether to a more reactive unit
(e.g., protonation with strong acids to an organic halide).8
Indeed, ethers are often useful as alcohol protecting groups
in many palladium-catalyzed reactions.
(4) For reviews of C-O oxidative addition: (a) Yamamoto, A. AdVances
in Organometallic Chemistry; Academic Press: San Diego, 1992; Vol. 34.
(b) Lin, Y. S; Yamamoto, A. Topics in Organometallic Chemstry; Murai,
S., Ed.; Springer-Verlag: Berlin, 1999; Vol. 3.
(5) (a) van der Boom, M. E.; Liou, S. Y.; Ben-David, Y.; Shimon, L. J.
W; Milstein, D. J. J. Am. Chem. Soc. 1998, 120, 6531. (b) Yamamoto, T.;
Akimoto, M.; Saito, O.; Yamamoto, A. Organometallics 1986, 5, 1559.
(6) Allylic ethers: (a) Acemoglu, L.; Williams, J. M. J. Handbook of
Organopalladium Chemistry for Organic Synthesis; Negishi, E., Ed.;
Wiley: Weinhiem, 2002; pp 1689. (b) Kayaki, Y.; Koda, T.; Ikariya, T.
Eur. J. Org. Chem. 2004, 4989. For propargyl ethers: (c) Cacchi, S.; Fabrizi,
G.; Moro, L. Tetrahedron Lett. 1998, 39, 5101. (d) Pal, M.; Parasuraman,
K.; Yeleswarapu, R. Org. Lett. 2003, 5, 349. Others: (e) Kakiuchi, F.;
Usui, M.; Uedo, S.; Chatani, N.; Murai, S. J. Am. Chem. Soc. 2004, 126,
2706.
(1) (a) De Meijere, A., Diederich, F., Eds. Metal-Catalyzed Cross-
Coupling Reactions; Wiley-VCH: Weinheim, 2004. (b) Tsuji, J., Ed. Topics
in Organometallic Chemistry; Springer-Verlag: Berlin 2005; Vol. 14,
(2) (a) Hartwig, J. F. Angew. Chem., Int. Ed. 1998, 37, 2046 (b) Wolfe,
J. P; Wagaw, S.; Marcoux, J.; Buchwald, S. L. Acc. Chem. Res. 1998, 31,
805. (c) Beller, M.; Eckert, M. Angew. Chem., Int. Ed. 2000, 39, 1010.
(3) The latter include H2 and other element-element bonds: Makabe,
H.; Negishi, E. Handb. Organopalladium Chem. Org. Synth. 2002, 2, 2789.
(7) (a) Sajiki, H.; Hattori, K.; Hirota, K. Chem. Eur. J. 2000, 6, 2200.
(b) Khumtaveeporn, K.; Alper, H. Acc. Chem. Res. 1995, 28, 414.
(8) Including amidocarbonylation (ref 2c) and the Monsanto acid
process: Yang, J.; Haynes, A.; Maitlis, P. M. Chem. Commun. 1999, 179.
10.1021/ol7021017 CCC: $37.00
© 2007 American Chemical Society
Published on Web 09/22/2007