C O M M U N I C A T I O N S
Au(I) are effective catalysts for this air- and moisture-tolerant
transformation that is characterized by mild conditions and excellent
functional group tolerance.
Acknowledgment. We gratefully acknowledge the University
of California, Berkeley, NIHGMS (R01 GM073932-01), Merck
Research Laboratories, Bristol-Myers Squibb, Amgen Inc., DuPont,
GlaxoSmithKline, Eli Lilly & Co., Pfizer, AstraZeneca, and Abbott
for financial support.
Supporting Information Available: Experimental procedures and
compound characterization data. This material is available free of charge
In many cases the silver-catalyzed naphthyl ketone synthesis
proceeded as well or better than the analogous gold(I)-cata-
lyzed reaction. For example, the conversion from 6f to 7f (entry
6) was catalyzed by 5% cationic triphenylphosphinegold(I) to
afford 7f in 48% yield; however, all attempts at silver-catalyzed
rearrangement of pyrrole 12 and enediyne 14 failed to produce the
desired aromatic ketones. In these cases, the analogous tri-tert-
butylphosphinegold(I)-catalyzed reactions delivered indole11 13 and
acetophenone 15 in 58 and 55% yield, respectively (eqs 4, 5).
References
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Chem. Soc. 2005, 127, 16342. (e) Lo, C.-Y.; Kumar, M. P.; Chang, H.-
K.; Lush, S.-F.; Liu, R.-S. J. Org. Chem. 2005, 70, 10482. (f) Taduri, B.
P.; Ran, Y.-F.; Huang, C.-W.; Liu, R.-S. Org. Lett. 2006, 8, 883.
(4) (a) Myers, A. G.; Harrington, P. M.; Kwon, B. M. J. Am. Chem. Soc.
1992, 114, 1086. (b) Sugiyama, H.; Fujiwara, T.; Kawabata, H.; Yoda,
N.; Hirayama, N.; Saito, I. J. Am. Chem. Soc. 1992, 114, 5573.
Mo-mediated carbonylation of allenyl arene-ynes gave byproducts derived
from the Myers-Saito rearrangement, see: (c) Datta, S.; Liu, R.-S.
Tetrahedron Lett. 2005, 46, 7985.
Notably, there is no preexisting aromatic ring required for the latter
transformation.
A mechanism involving sequential rearrangements promoted by
transition-metal activation of the alkynes is envisioned (Scheme
1).12 First, coordination of the metal to the propargyl ester produces
Scheme 1. Proposed Mechanism
(5) (a) Johansson, M. J.; Gorin, D. J.; Staben, S. T.; Toste, F. D. J. Am. Chem.
Soc. 2005, 127, 18002. (b) Kennedy-Smith, J. J.; Staben, S. T.; Toste, F.
D. J. Am. Chem. Soc. 2004, 126, 4526. (c) Luzung, M. R.; Markham, J.
P.; Toste, F. D. J. Am. Chem. Soc. 2004, 126, 10858. (d) Markham, J. P.;
Staben, S. T.; Toste, F. D. J. Am. Chem. Soc. 2005, 127, 9708. (e) Gorin,
D. J.; Davis, N. R.; Toste, F. D. J. Am. Chem. Soc. 2005, 127, 11260. (f)
Shi, X. D.; Gorin, D. J.; Toste, F. D. J. Am. Chem. Soc. 2005, 127, 5802.
(g) Staben, S. T.; Kennedy-Smith, J. J.; Toste, F. D. Angew. Chem., Int.
Ed. 2004, 43, 5350.
(6) For Au(III)-catalyzed benzannulations see: (a) Hashmi, A. S. K.; Frost,
T. M.; Bats, J. W. J. Am. Chem. Soc. 2000, 122, 11553. (b) Hashmi, A.
S. K.; Frost, T. M.; Bats, J. W. Org. Lett. 2001, 3, 3769. (c) Dankwardt,
J. W. Tetrahedron Lett. 2001, 42, 5809. (d) Hashmi, A. S. K.; Rudolph,
M.; Weyrauch, J. P.; Wo¨lfe, M.; Frey, W.; Bats, J. W. Angew Chem., Int.
Ed. 2005, 44, 2798. (e) Asao, N.; Aikawa, H.; Yamamoto, Y. J. Am. Chem.
Soc. 2004, 126, 7458. (f) Asao, N.; Nogami, T.; Lee, S.; Yamamoto, Y.
J. Am. Chem. Soc. 2003, 125, 10921. (g) Asao, N.; Takahashi, K.; Lee,
S.; Kasahara, T.; Yamamoto, Y. J. Am. Chem. Soc. 2002, 124, 12650.
(7) Reaction of 4a with 5% Sc(OTf)3 5% PdCl2(MeCN)2, 10% CuBr or 10%
Cu(OTf) ‚PhCH3 did not afford 5a; 5% PtCl4 gave 13% of 5a.
(8) The nature of the catalytically active Ag(I) species is not known at this
time. Monitoring the reaction by 31P NMR shows the formation of (Ph3P)-
AgBF4; however, independently prepared (Ph3P)AgBF4 does not catalyze
the conversion of 4a to 5a at room temperature.
(9) In accord with this hypothesis, 10% AgOAc does not catalyze the reaction.
For use of MgO as an acid scavenger, see: Espino, C. G.; Du Bois, J.
Angew. Chem., Int. Ed. 2001, 40, 598.
(10) Ag(I)-catalyzed reaction of enantioenriched 8 (93% ee) gave racemic 9.
(11) For synthesis of indoles by [4 + 2]-benzannulation see: Dunetz, J. R.;
Danheiser, R. L. J. Am. Chem. Soc. 2005, 127, 5776 and references therein.
(12) For recent examples of Ag(I)- or Au(I)-catalyzed tandem reactions initiated
by [3,3]-rearrangements of propargyl acetates see: (a) Zhang, L. J. Am.
Chem. Soc. 2005, 127, 16804. (b) Sromek, A. W.; Kelin, A. V.;
Gevorgyan, V. Angew. Chem., Int. Ed. 2004, 43, 2280.
enyne allene through a [3,3]-sigmatropic rearrangement (Cycle A).
Activation of the remaining alkyne induces 6-endo-dig addition of
the allenyl acetate (Cycle B).13 In accord with this hypothesis, enyne
allene 16 could be isolated from the silver-catalyzed reaction of 6f
(eq 6). Resubjecting 16 to the reaction conditions afforded expected
naphthyl ketone 7f in 94% yield (eq 6).
(13) A mechanism involving a Myers-Saito diradical intermediate is also
possible; however, no cyclopropyl ring-opening (see: Dopico, P. G.; Finn,
M. G. Tetrahedron 1999, 55, 29) was observed in the Ag-catalyzed
rearrangement of 17 to cyclopropyl ketone 18.
In conclusion, we have developed a transition metal-cata-
lyzed tandem [3,3]-sigmatropic rearrangement/formal Myers-Saito
cyclization of propargyl esters to form aromatic ketones. A
mechanism in which the metal catalyzes both of these processes
through alkyne activation is proposed. Both simple Ag(I) and
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