ORGANIC
LETTERS
[(NHC)AuI]-Catalyzed Rearrangement of
Allylic Acetates
2007
Vol. 9, No. 14
2653-2656
Nicolas Marion, Ronan Gealageas, and Steven P. Nolan*
Institute of Chemical Research of Catalonia (ICIQ), AV. Pa¨ısos Catalans 16,
43007 Tarragona, Spain
Received April 10, 2007
ABSTRACT
[(NHC)AuCl] complexes (NHC
) N-heterocyclic carbene), in conjunction with a silver salt, were found to efficiently catalyze the rearrangement
of allylic acetates under both conventional and microwave-assisted heating. The optimization of several reaction parameters (solvent, silver
salt, and ligand) as well as a study of the reaction scope are reported. The steric hindrance of the ligand bound to gold was found crucial for
the outcome of the reaction as only extremely bulky ligands permitted the isomerization.
Homogeneous gold catalysis has emerged lately as an
efficient tool for the construction of complex organic
molecules, notably through functionalization of alkynes and
allenes.1 AuI and AuIII complexes generally act as soft π-acids
and coordinate to the CtC bond (or to the allene), triggering
inter- and intramolecular nucleophilic attacks. This type of
catalysis can be applied to alkenes as well but presents a
more limited scope,2 X-H addition (X ) N, O) across the
CdC bond being the most studied process.3
While propargylic acetates continue to be extensively
studied for their valuable reactivity in the presence of gold
catalysts,4 almost no attention has been paid to their allylic
counterparts.5 Similarly to propargylic esters,6 we envisaged
that the acetate moiety might undergo a 1,3-shift upon
complexation of Au+ fragment onto the alkene, resulting
ultimately in the formation of an isomerized allylic acetate.
This reaction, namely the allylic rearrangement, provides an
(3) For N-H addition, see: (a) Zhang, J.; Yang, C.-G.; He, C. J. Am.
Chem. Soc. 2006, 128, 1798-1799. (b) Brouwer, C.; He, C. Angew. Chem.,
Int. Ed. 2006, 45, 1744-1747. (c) Li, Z.; Ding, X.; He, C. J. Org. Chem.
2006, 71, 5876-5880. (d) Han, X.; Widenhoefer, R. A. Angew. Chem.,
Int. Ed. 2006, 45, 1747-1749. (e) Liu, X.-Y.; Li, C.-H.; Che, C.-M. Org.
Lett. 2006, 8, 2707-2710. (f) Bender, C. F.; Widenhoefer, R. A. Chem.
Commun. 2006, 4143-4144. (g) Bender, C. F.; Widenhoefer, R. A. Org.
Lett. 2006, 8, 5303-5305. For O-H addition, see: (h) Yang, C.-G.; He,
C. J. Am. Chem. Soc. 2005, 127, 6966-6967. (i) Nguyen, R.-V.; Yao, X.;
Li, C.-J. Org. Lett. 2006, 8, 2397-2399. (j) Skouta, R.; Li, C.-J. Angew.
Chem., Int. Ed. 2007, 46, 1117-1119.
(4) For an overview, see: Marion, N.; Nolan, S. P. Angew. Chem., Int.
Ed. 2007, 46, 2750-2752.
(5) During the redaction of this manuscript, a study on the isomerization
of allenyl esters, a peculiar class of allylic acetates, catalyzed by AuI
complexes appeared, see: Buzas, A. K.; Istrate, F. M.; Gagosz, F. Org.
Lett. 2007, 9, 985-988.
(6) For Au-mediated 1,3-shift of propargylic esters, see: (a) Fu¨rstner,
A.; Hannen, P. Chem. Commun. 2004, 2546-2547. (b) Zhang, L. J. Am.
Chem. Soc. 2005, 127, 16804-16805. (c) Zhang, L.; Wang, S. J. Am. Chem.
Soc. 2006, 128, 1442-1443. (d) Buzas, A.; Istrate, F.; Gagosz, F. Org.
Lett. 2006, 8, 1957-1959. (e) Wang, S.; Zhang, L. J. Am. Chem. Soc. 2006,
128, 8414-8415. (f) Wang, S.; Zhang, L. Org. Lett. 2006, 8, 4585-4587.
(g) Oh, C. H.; Kim, A.; Park, W.; Park, D. I.; Kim, N. Synlett 2006, 2781-
2784. (h) Buzas, A.; Gagosz, F. J. Am. Chem. Soc. 2006, 128, 12614-
12615. (i) Lemie`re, G.; Gandon, V.; Cariou, K.; Fukuyama, T.; Dhimane,
A.-L.; Fensterbank, L.; Maiacria, M. Org. Lett. 2007, 9, 2207-2209.
(1) For recent reviews, see: (a) Marco-Contelles, J.; Soriano, E. Chem.
Eur. J. 2007, 13, 1350-1357. (b) Jime´nez-Nu´n˜ez, E.; Echavarren, A. M.
Chem. Commun. 2007, 333-346. (c) Zhang, L.; Sun, J.; Kozmin, S. A.
AdV. Synth. Catal. 2006, 348, 2271-2296. (d) Hashmi, A. S. K.; Hutchings,
G. J. Angew. Chem., Int. Ed. 2006, 45, 7896-7936. (e) Fu¨rstner, A.; Davies,
P. W. Angew. Chem. Int. Ed. 2007, 46, 3410-3449.
(2) For alkene activation in Au catalysis, see: (a) Hashmi, A. S. K.;
Schwarz, L.; Choi, J.-H.; Frost, T. M. Angew. Chem., Int. Ed. 2000, 39,
2285-2288. (b) Dyker, G.; Muth, E.; Hashmi, A. S. K.; Ding, L. AdV.
Synth. Catal. 2003, 345, 1247-1252. (c) Yao, X.; Li, C.-J. J. Am. Chem.
Soc. 2004, 126, 6884-6885. (d) Alfonsi, M.; Arcadi, A.; Aschi, M.; Bianchi,
G.; Marinelli, F. J. Org. Chem. 2005, 70, 2265-2273. (e) Xing, D.; Guan,
B.; Cai, G.; Fang, Z.; Yang, L.; Shi, Z. Org. Lett. 2006, 8, 693-696. (f)
Alfonsi, M.; Arcadi, A.; Bianchi, G.; Marinelli, F.; Nardini, A. Eur. J. Org.
Chem. 2006, 2393-2402.
10.1021/ol070843w CCC: $37.00
© 2007 American Chemical Society
Published on Web 06/08/2007