Download PDF
Synlett 2008(5): 755-758  
DOI: 10.1055/s-2008-1042810
CLUSTER
© Georg Thieme Verlag Stuttgart · New York

[Ir(cod)Cl]2/FDPPE-Catalyzed Chemo- and Regioselective Cyclotrimerization of Two Different Terminal Alkynes To Give 1,3,5-Trisubstituted Benzenes

Gen Onodera, Masayoshi Matsuzawa, Takahiro Aizawa, Takeshi Kitahara, Yoshihisa Shimizu, Satoko Kezuka, Ryo Takeuchi*
Department of Chemistry and Biological Science, Aoyama Gakuin University, Fuchinobe, Sagamihara 229-8558, Japan
Fax: +81(42)7596493; e-Mail: takeuchi@chem.aoyama.ac.jp;
Further Information

Publication History

Received 29 November 2007
Publication Date:
26 February 2008 (online)

    Permissions and Reprints All articles of this category

Abstract

[Ir(cod)Cl]2 in combination with 1,2-bis(dipentafluorophenylphosphino)ethane catalyzes chemo- and regioselective cyclotrimerization of two different alkynes. The reaction of methyl propiolate with 1-hexyne gave methyl 3,5-di(n-butyl)benzoate as a single product in 88% yield.

Key words

iridium - cyclotrimerization - regioselectivity - alkynes - catalysis

1

Present address: Department of Applied Chemistry, Tokai University, Hiratsuka, 259-1292, Japan.

6

Typical Experimental Procedure for the Reaction of Methyl Propiolate (1a) with 1-Hexyne (2a) Catalyzed by [Ir(cod)Cl] 2 /FDPPE and Spectral Data of Methyl 3,5-Di( n -butyl)benzoate (3aa) Into a two-necked flask with a stirring bar were placed [IR (cod)Cl]2 (13.6 mg, 0.02 mmol) and FDPPE (30.9 mg, 0.040 mmol). The flask was evacuated and filled with Ar. Then, anhydrous THF (5.0 mL) was added to the flask. To the stirred solution was added 1-hexyne (2a, 243 mg, 3.0 mmol). Methyl propiolate (1a, 83.3 mg, 1.0 mmol) was then added dropwise to the reaction mixture. The reactor was immersed in an oil bath, which was kept at 75 °C. The reaction mixture was heated under reflux for 1 h. The progress of the reaction was monitored by GLC. After the reaction was completed, the solvent was concentrated in vacuo. Column chromatography of the residue gave 3aa as a colorless oil (n-hexane-EtOAc = 99:1, 219 mg, yield 88%). 1H NMR (500 MHz, CDCl3): δ = 0.93 (t, J = 7.3 Hz, 6 H), 1.35 (sext, J = 7.3 Hz, 4 H), 1.58-1.64 (m, 4 H), 2.62 (t, J = 7.8 Hz, 4 H), 3.90 (s, 3 H), 7.18 (s, 1 H), 7.68 (d, J = 1.8 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 13.9 (2 C), 22.3 (2 C), 33.6 (2 C), 35.4 (2 C), 51.9, 126.9 (2 C), 130.1, 133.4, 143.1 (2 C), 167.6. Anal. Calcd for C16H24O2: C, 77.38; H, 9.74; O, 12.88. Found: C, 77.49; H, 9.74.

7

All new compounds were fully characterized.

10

Typical Procedure for the Reaction of 3aa To Give 3,5-Di( n -butyl)benzaldehyde (4aa) and Spectral Data of 4aa
A flask was charged with LiAlH4 (57 mg, 1.5 mmol). The flask was evacuated and filled with argon. To the flask was added Et2O (3 mL). An ether solution (3.0 mL) of benzoate 3aa (248 mg, 1 mmol) was added dropwise to the reaction mixture. The mixture was stirred at r.t. for 4 h. The progress of the reaction was monitored by TLC. After the reaction was complete, the mixture was poured into 2 M HCl, and the aqueous layer was extracted with Et2O. The combined organic layers were washed with a solution of sat. aq NaHCO3 and dried with Mg2SO4. The solvent was evaporated in vacuo. Another flask was charged with MnO2 (869 mg, 10 mmol). The flask was evacuated and filled with argon. Then, CH2Cl2 (2 mL) was added to the flask. The CH2Cl2 solution (3 mL) of the residue was then added to the stirred reaction mixture. The reaction mixture was stirred at r.t. for 30 h. The progress of the reaction was monitored by GLC and TLC. After the reaction was complete, the mixture was filtered through a Celite pad. The solution was evaporated in vacuo. Column chromatography of the residue gave 4aa as a colorless oil (n-hexane-EtOAc = 99:1, 192 mg, yield 88%). 1H NMR (500 MHz, CDCl3): δ = 0.94 (t, J = 7.3 Hz, 6 H), 1.36 (sext, J = 7.3 Hz, 4 H), 1.59-1.65 (m, 4 H), 2.66 (t, J = 7.8 Hz, 4 H), 7.26 (s, 1 H), 7.51 (d, J = 1.4 Hz, 2 H), 9.97 (s, 1 H). 13C NMR (125 MHz, CDCl3): δ = 13.9 (2 C), 22.3 (2 C), 33.4 (2 C), 35.3 (2 C), 127.1 (2 C), 135.0, 136.6, 143.8 (2 C), 192.8. HRMS: m/z calcd for C15H22O [M+]: 218.1671; found: 218.1651.