LETTER
Au2O3 as Catalyst for the Selective Cycloisomerization of g-Acetylenic Carboxylic Acids
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Barange, D.; Pal, M. J. Org. Chem. 2005, 70, 4778.
(j) Duchêne, A.; Thibonnet, J.; Parrain, J.-L.; Anselmi, E.;
Abarbri, M. Synthesis 2007, 597.
trifluoromethylsulfonate ester (1.1 equiv) slowly added. The
mixture was stirred at r.t. overnight, quenched upon addition
of 10 mL of H2O and extracted with Et2O (3 × 20 mL). The
combined organic layers were washed with brine (30 mL),
dried over MgSO4, and solvents evaporated under reduced
pressure. Dimethyl 2-(but-3-ynyl)-2-(prop-2-ynyl)malonate
was obtained as a colorless oil (18%) after purification by
silica gel chromatography (cyclohexane–EtOAc, 90:10).
Monosaponification was conducted following a reported
procedure.14 A solution of KOH (1.2 equiv) in anhydrous
MeOH (0.4 mol/L) was added to a cooled (0 °C) solution of
substrate (1 equiv) in anhydrous MeOH (0.4 mol/L). The
mixture was stirred at r.t. for 6 h. Solvent was removed under
reduced pressure and the crude product redissolved in Et2O.
The organic layer was treated three times with sat. NaHCO3,
the aqueous phases collected, acidified to pH 1 with concd
HCl, and then extracted with Et2O. This organic layer was
then dried over MgSO4 and the solvents removed under
reduced pressure to give 1i as a colorless oil (48% yield).
2-Methoxycarbonyl-2-[but-3¢-ynyl]-4-methylene-
butyrolactone (2i)
(10) Ruthenium catalysis: Jimenez-Tenotio, M.; Puerta, M. C.;
Valerga, P.; Moreno-Dorado, F. J.; Guerra, F. M.; Massanet,
G. M. Chem. Commun. 2001, 2324.
(11) Rhodium catalysis: (a) Marder, T. B.; Chan, D. M. T.; Fultz,
W. C.; Calabrese, J. C.; Milstein, D. J. Chem. Soc., Chem
Commun. 1987, 1885. (b) Chan, D. M. T.; Marder, T. B.;
Milstein, D.; Taylor, N. J. J. Am. Chem. Soc. 1987, 109,
6385. (c) Elgafi, S.; Field, L. D.; Messerle, B. A.
J. Organomet. Chem. 2000, 607, 97.
(12) Cluster catalysis: (a) Wakabayashi, T.; Ishii, Y.; Ishikawa,
K.; Hidai, M. Angew. Chem., Int. Ed. Engl. 1996, 35, 3123;
and references cited therein. (b) Takei, I.; Wakebe, Y.;
Suzuki, K.; Enta, Y.; Suzuki, T.; Mizobe, Y.; Hidai, M.
Organometallics 2003, 22, 4639.
(13) (a) Charruault, L.; Michelet, V.; Taras, R.; Gladiali, S.;
Genêt, J.-P. Chem. Commun. 2004, 850. (b) Nevado, C.;
Charruault, L.; Michelet, V.; Nieto-Oberhuber, C.; Muñoz,
M. P.; Méndez, M.; Rager, M.-N.; Genêt, J.-P.; Echavarren,
A. M. Eur. J. Org. Chem. 2003, 706. (c) Antoniotti, S.;
Genin, E.; Michelet, V.; Genêt, J.-P. J. Am. Chem. Soc.
2005, 127, 9976. (d) Genin, E.; Antoniotti, S.; Michelet, V.;
Genêt, J.-P. Angew. Chem. Int. Ed. 2005, 44, 4949.
(e) Toullec, P. Y.; Genin, E.; Leseurre, L.; Genêt, J.-P.;
Michelet, V. Angew. Chem. Int. Ed. 2006, 45, 7427.
(f) Genin, E.; Leseurre, L.; Toullec, P. Y.; Genêt, J.-P.;
Michelet, V. Synlett 2007, 1780. (g) Leseurre, L.; Toullec,
P. Y.; Genêt, J.-P.; Michelet, V. Org. Lett. 2007, 9, 4049.
(14) (a) Genin, E.; Toullec, P. Y.; Antoniotti, S.; Brancour, C.;
Genêt, J.-P.; Michelet, V. J. Am. Chem. Soc. 2006, 128,
3112. (b) Genin, E.; Toullec, P. Y.; Antoniotti, S.; Brancour,
C.; G enêt, J.-P.; Michelet, V. ARKIVOC 2007, (v), 67.
(15) For references dealing with the gold-catalyzed hydration of
alkynes, see: (a) Fukuda, Y.; Utimoto, K. J. Org. Chem.
1991, 56, 3729. (b) Teles, J. H.; Brode, S.; Chabanas, M.
Angew. Chem. Int. Ed. 1998, 37, 1415. (c) Mizushima, E.;
Sato, K.; Hayashi, T. M. Angew. Chem. Int. Ed. 2002, 41,
4563. (d) Schneider, S. K.; Herrmann, W. A.; Herdtweck, E.
Z. Anorg. Allg. Chem. 2003, 629, 2363.
1H NMR (300 MHz, CDCl3): d = 4.80–4.83 (m, 1 H), 4.39–
4.41 (m, 1 H), 3.79 (s, 3 H), 3.39 (dt, J = 18.9, 2.0 Hz, 1 H),
2.98 (dt, J = 18.9, 2.0 Hz, 1 H), 2.05–2.40 (m, 4 H), 1.99 (t,
J = 2.6 Hz, 1 H). 13C NMR (75.4 MHz, CDCl3): d = 171.9,
168.9, 152.3, 89.9, 82.1, 69.8, 54.6, 53.4, 35.3, 32.6, 14.3.
MS (CI, NH3): m/z (%) = 209 (8) [M + H]+, 226 (100) [M +
NH4]+, 244 (8) [M + NH3 + NH4]+. HRMS (CI-NH3): m/z
calcd for C11H13O4: 209.0814; found: 209.0819.
(20) 2,2-Dimethylhept-4-ynoic Acid (1l)
Methyl isobutyrate (1.07g, 10.5 mmol) was added dropwise
at –78 °C to a solution of LDA solution in THF (15 mL, 0.7
mol/L, 10.5 mmol). The solution was stirred at –78 °C for 20
min then 1-bromobut-2-yne (1.47g, 10 mmol) slowly added
dropwise. The reaction was stirred at –78 °C for 2 h then
allowed to warm up to r.t. The reaction mixture was
quenched with sat. aq NaHCO3 solution and extracted with
Et2O. The combined organic layers were collected, washed
with brine, dried over MgSO4, and the solvents removed
under reduced pressure. The crude oil was purified by flash
chromatography [PE (30–60)–EtOAc, 95:5] to give methyl
2,2-dimethylhept-4-ynoate as a colorless oil (1.48 g, 88%
yield). Saponification was conducted following a published
procedure.2 Methyl 2,2-dimethylhept-4-ynoate (1.01g, 6
mmol) was added to a solution of KOH (403 mg, 7.2 mmol)
in MeOH and the reaction mixture was stirred at r.t. for 16 h.
Solvent was removed under reduced pressure and the crude
product dissolved in Et2O. The organic layer was treated
three times with sat. Na2CO3, the aqueous phases collected,
acidified to pH 1 with concd HCl, and then extracted with
Et2O. This organic layer was then dried over MgSO4 and the
solvents removed under reduced pressure to give 1l as a
colorless oil (590 mg, 64% yield). 1H NMR (300 MHz,
CDCl3): d = 2.41 (t, J = 2.4 Hz, 2 H), 2.16 (qt, J = 7.5, 2.4
Hz, 2 H), 1.28 (s, 3 H), 1.11 (t, J = 7.5 Hz, 1 H). 13C NMR
(75.4 MHz, CDCl3): d = 183.2, 84.3, 75.5, 42.2, 29.7, 24.3,
14.2, 12.4. MS (CI, NH3): m/z (%) = 155 (15) [M + H]+) 172
(100) [M + NH4]+. HRMS (CI-NH3): m/z calcd for C9H15O2:
155.1072; found: 155.1075.
(16) (a) Harkat, H.; Weibel, J.-M.; Pale, P. Tetrahedron Lett.
2006, 47, 6273. (b) For a recent Au-catalyzed cyclization of
g- and d-acetylenic acids, see: Marchal, E.; Uriac, P.;
Legoin, B.; Toupet, L.; van de Weghe, P. Tetrahedron 2007,
63, 9979.
(17) (a) Jones, C. J.; Taube, D.; Ziatdinov, V. R.; Periana, R. A.;
Nielsen, R. J.; Oxgaard, J.; Goddard, W. A. III. Angew.
Chem. Int. Ed. 2004, 43, 4626. (b) De Vos, D. E.; Sels, B. F.
Angew. Chem. Int. Ed. 2005, 44, 30.
(18) General Procedure for the Cycloisomerization of
g-Acetylenic Acid 1
Substrate 1b (98 mg, 1 mmol) was placed in 5 mL Schlenk
tube under argon and 1 mL of degassed MeCN was added.
Gold(III) oxide (11.1 mg, 0,025 mmol) was added and the
reaction mixture stirred at r.t. for 2 h. Filtration of the
reaction mixture on a pad of 2 cm of silica using 15 mL of
EtOAc and evaporation of the solvents allowed the isolation
of product 2b as colorless oil in an analytically pure form (89
mg, 90% yield).
2,2-Dimethyl-4-propylydenebutyrolactone (2l)
(19) 2-(Methoxycarbonyl)-2-(prop-2-ynyl)hex-5-ynoic Acid
(1i)
1H NMR (300 MHz, CDCl3): d = 4.60 (tt, J = 7.4, 1.7 Hz, 1
H), 2.61 (dt, J = 1.5, 1.5 Hz, 2 H), 2.16 (dtq, J = 7.5, 7.4, 1.4
Hz, 2 H), 1.29 (s, 6 H), 0.98 (t, J = 7.5 Hz, 3 H). 13C NMR
(75.4 MHz, CDCl3): d = 180.4, 144.8, 107.2, 40.8, 40.0,
24.6, 18.5, 14.2. MS (CI, NH3): m/z (%) 172 (20) [M +
NH4]+, 188 (100) [M + NH4 + H2O]+. HRMS (CI-NH3): m/z
calcd for C9H15O2: 155.1072; found: 155.1071.
Substrate 1i was prepared in a two-step procedure using
malonic synthesis. Sodium hydride (1.1 equiv, 60 wt.% in
mineral oil) was added portionwise at 0 °C to a solution of
dimethyl propargylmalonate (1 equiv) in anhydrous DMF.
The reaction was allowed to warm up to r.t. and but-3-ynyl
Synlett 2008, No. 5, 707–711 © Thieme Stuttgart · New York