C O M M U N I C A T I O N S
Aryl-substituted enynes 9a-f react with catalysts 1a-d to give
2,3,9,9a-tetrahydro-1H-cyclopenta[b]naphthalenes 10a-f 11 in good
yields by intramolecular [4 + 2] cycloadditions (Table 2). Cycliz-
ation with [Au(PPh3)]SbF6 requires longer reaction times (Table
2, entry 2). In the case of 9c, the aryl group reacts at the least
substituted position to give 10c (Table 2, entry 4). On the other
hand, 10d-f are obtained as single stereoisomers, as a result of
retention of the alkene configuration. Although satisfactory results
are obtained with 1a or 1b, complex 1d is the precatalyst of choice
for the cyclization of the less reactive substrates.
biphenyl phosphines as ligands. Best results are obtained with
complex 1d, which bears an electron-rich aryl ring. While thermal
intramolecular [4 + 2] cycloadditions (dehydro-Diels-Alder reac-
tions) of enynes with alkenes only take place at high temperatures,12
these transformations proceed with Au(I) catalysts under mild
conditions to provide bi- or tricyclic ring systems.
Acknowledgment. This work was supported by the MEC
(CTQ2004-02869, predoctoral fellowship to C.N.-O., and post-
doctoral contract to S.L.), and the ICIQ Foundation. We also
acknowledge Johnson Matthey PLC for a loan of metal salts.
Table 2. Au(I)-Catalyzed Cyclization of 9a-f (Z ) C(CO2Me)2)
Supporting Information Available: Additional experiments and
characterization data. This material is available free of charge via the
References
(1) Reviews: (a) Lloyd-Jones, G. C. Org. Biomol. Chem. 2003, 215-236.
(b) Aubert, C.; Buisine, O.; Malacria, M. Chem. ReV. 2002, 102, 813-
834. (c) Diver, S. T.; Giessert, A. J. Chem. ReV. 2004, 104, 1317-1382.
(d) Echavarren, A. M.; Nevado, C. Chem. Soc. ReV. 2004, 33, 431-436.
(2) (a) Me´ndez, M.; Mun˜oz, M. P.; Nevado, C.; Ca´rdenas, D. J.; Echavarren,
A. M. J. Am. Chem. Soc. 2001, 123, 10511-10520. (b) Nevado, C.;
Ca´rdenas, D. J.; Echavarren, A. M. Chem.sEur. J. 2003, 9, 2627-2635.
(c) Mun˜oz, M. P.; Adrio, J.; Carretero, J. C.; Echavarren, A. M.
Organometallics 2005, 24, 1293-1300.
(3) (a) Trost, B. M.; Tanoury, G. J. J. Am. Chem. Soc. 1988, 110, 1636-
1638. (b) Trost, B. M.; Trost, M. K. Tetrahedron Lett. 1991, 32, 3647-
3650. (c) Chatani, N.; Morimoto, T.; Muto, T; Murai, S. J. Am. Chem.
Soc. 1994, 116, 6049-6050. (d) Chatani, N.; Furukawa, N.; Sakurai, H.;
Murai, S. Organometallics 1996, 15, 901-903. (e) Fu¨rstner, A.; Szillat,
H. F.; Gabor, B.; Mynott, R. J. Am. Chem. Soc. 1998, 120, 8305-8314.
(f) Trost, B. M.; Doherty, G. A. J. Am. Chem. Soc. 2000, 122, 3801-
3810. (g) Fu¨rstner, A.; Szillat, H.; Stelzer, F. J. Am. Chem. Soc. 2000,
122, 6785-6786. (h) Fu¨rstner, A.; Stelzer, F.; Szillat, H. J. Am. Chem.
Soc. 2001, 123, 11863-11869. (i) Oi, S.; Tsukamoto, I.; Miyano, S.; Inoue,
Y. Organometallics 2001, 20, 3704-3709. (j) Chatani, N.; Inoue, H.;
Morimoto, T.; Muto, T.; Murai, S. J. Org. Chem. 2001, 66, 4433-4436.
(k) Chatani, N.; Inoue, H.; Kotsuma, T.; Murai, S. J. Am. Chem. Soc.
2002, 124, 10294-10295. (l) Oh, C. H.; Bang, S. Y.; Rhim, C. Y. Bull.
Korean Chem. Soc. 2003, 24, 887-888. (m) Peppers, B. P.; Diver, S. T.
J. Am. Chem. Soc. 2004, 126, 9524-9525. (n) Miyanohana, Y.; Inoue,
H.; Chatani, N. J. Org. Chem. 2004, 69, 8541-8543. (o) Bajracharya, G.
B.; Nakamura, I.; Yamamoto, Y. J. Org. Chem. 2005, 70, 892-897.
(4) (a) Nieto-Oberhuber, C.; Mun˜oz, M. P.; Bun˜uel, E.; Nevado, C.; Ca´rdenas,
D. J.; Echavarren, A. M. Angew. Chem., Int. Ed. 2004, 43, 2402-2406.
(b) Mamane, V.; Gress, T.; Krause, H.; Fu¨rstner, A. J. Am. Chem. Soc.
2004, 126, 8654-8655. (c) Zhang, L.; Kozmin, S. A. J. Am. Chem. Soc.
2004, 126, 11806-11807. (d) Luzung, M. R.; Markham, J. P.; Toste, F.
D. J. Am. Chem. Soc. 2004, 126, 10858-10859.
entry
enyne
[Au(I)]
time (h)
product
yield (%)
1
2
3
4
5
6
7
8
9
9a
9a
9b
9c
9d
9d
9e
9e
9e
9f
1a
1
12
12
3
12
12
36
20
18
48
10a
10a
10b
10c
10d
10d
10e
10e
10e
10f
86
83
96
53
43
67
51
45
76
64
[Au(PPh3)Cl]
1d
1d
1a
1d
1a
1b
1d
1d
10
Scheme 3. Proposed Mechanism for the Au(I)-Catalyzed
Cyclization of Enynes 9a-f (Z ) C(CO2Me)2)
(5) Strieter, E. R.; Blackmond, D. G.; Buchwald, S. L. J. Am. Chem. Soc.
2003, 125, 13978-13980.
(6) (a) Walker, S. D.; Border, T. E.; Martinelli, J. R.; Buchwald, S. L. Angew.
Chem., Int. Ed. 2004, 43, 1871-1876. (b) Kaye, S.; Fox, J. M.; Hicks, F.
A.; Buchwald, S. L. Adv. Synth. Catal. 2001, 343, 789-794.
(7) See Supporting Information for additional examples.
(8) Au(I) complexes with N-heterocyclic ligands: (a) Bovio, B.; Burini, A.;
Pietroni, B. R. J. Organomet. Chem. 1993, 452, 287-291. (b) Hu, X.;
Castro-Rodriguez, I.; Olsen, K.; Meyer, K. Organometallics 2004, 23,
755-764 and references therein.
(9) For the involvement of intermediates of type VI: (a) Trost, B. M.; Hashmi,
A. S. K. Angew. Chem., Int. Ed. Engl. 1993, 32, 1085-1087. (b) Trost,
B. M.; Hashmi, A. S. K. J. Am. Chem. Soc. 1994, 116, 2183-2184.
(10) Regioselective proton loss occurs under kinetic control, as products 6a,b
are 2.5-3.5 kcal‚mol-1 less stable than dienes such as 7 (PM3 calcula-
tions).
(11) Synthesis of this ring system by Heck reaction and intramolecular
arylation: (a) Brown, S.; Clarkson, S.; Grigg, R.; Sridharan, V. Tetra-
hedron Lett. 1993, 34, 157-160. (b) Coudanne, I.; Balme, G. Synlett 1998,
998-1000. (c) See also: Ohno, H.; Miyaura, K.; Takeoka, Y.; Tanaka,
T. Angew. Chem., Int. Ed. 2003, 42, 2647-2650.
(12) Burrell, R. C.; Daoust, K. J.; Bradley, A. Z.; DiRico, K. J.; Johnson, R.
P. J. Am. Chem. Soc. 1996, 118, 4218-4219.
Cyclization of enynes 9a-f follows a 5-exo-dig pathway to form
cyclopropyl Au(I) carbene VIII (Scheme 3), which then probably
evolves by a Nazarov-type cyclization to form IX. This transforma-
tion can also be view as an opening of the cyclopropane of VIII
by the electron-rich aryl ring.
Enynes 9g,h give 11a,b under these conditions (eq 2), which
suggests that the transformation of Scheme 3 proceeds with
substrates bearing alkenes substituted at the terminal position with
groups capable of stabilizing the developing positive charge.
Cyclobutenes related to 11 had been obtained by Trost using
palladacyclopentadienes as catalysts.3a,b
In summary, we have found novel reactivity of substituted
1,6-enynes by using highly alkynophilic Au(I) complexes 1a,d with
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