Subscribe to RSS
DOI: 10.1055/s-2005-872266
Solvent-Free Synthesis of 2-Pyrones from Alkynes and Carbon Dioxide Catalyzed by Ni(1,5-cyclooctadiene)2/Trialkylphosphine Catalysts
Publication History
Publication Date:
03 August 2005 (online)
Abstract
Solvent-free, efficient, and mild 2-pyrone synthesis by the cycloaddition of alkynes with CO2 has been achieved under compressed CO2 with a Ni(cod)2/P(C4H9)3 or Ni(cod)2/P(C8H17)3 catalyst; both high yields (up to 98%) and selectivities (up to 99%) are attained. One attractive aspect of these catalysts is their high efficiency at low CO2 pressures (4 MPa). The applicability of this reaction to a broad range of alkyne substrates and the ease of handling the phosphine ligands are additional merits of the present new catalytic systems in comparison to the previously reported Ni(cod)2/P(CH3)3 catalyst in supercritical CO2.
Key words
2-pyrone derivatives - alkynes - carbon dioxide - Ni(0) complex - solvent-free
-
1a
Inoue Y.Itoh Y.Kazama H.Hashimoto H. Bull. Chem. Soc. Jpn. 1980, 53: 3329 -
1b
Walther D.Schönberg H.Dinjus E.Sieler J. J. Organomet. Chem. 1987, 334: 377 -
1c
Tsuda T.Morikawa S.Sumiya R.Saegusa T. J. Org. Chem. 1988, 53: 3140 -
1d
Louie J.Gibby JE.Farnworth MV.Tekavec TN. J. Am. Chem. Soc. 2002, 124: 15188 - 2 For a discussion of the chemistry of 2-pyrone, see:
Stauton J. In Comprehensive Organic Chemistry Vol. 4:Samnes PG. Pergamon Press; Oxford: 1979. p.629 -
3a
Kvita V.Fischer W. Chimia 1992, 46: 457 -
3b
Kvita V.Fischer W. Chimia 1993, 47: 3 - 4 For a synthesized 2-pyrone with anti-HIV activity, see:
Vara Prasad JVN.Para KS.Lunney EA.Ortwine DF.Dunbar JB.Ferguson D.Tummino PJ.Hupe D.Tait BD.Domagala JM.Humblet C.Bhat TN.Liu B.Guerin DMA.Baldwin ET.Erickson JW.Sawyer TK. J. Am. Chem. Soc. 1994, 116: 6989 - 5
Benign by Design. Alternative Synthetic Design for Pollution Prevention
Vol. 577:
Anastas PT.Farris CA. American Chemical Society; Washington DC: 1994. - 6
Eckert CA.Knutson BL.Debenedetti PG. Nature (London, U.K.) 1996, 383: 313 - 7
Chemical Synthesis Using Supercritical Fluids
Jessop PG.Leitner W. Wiley-VCH; Weinheim: 1999. - 8
Reetz MT.Könen W.Strack T. Chimia 1993, 47: 493 - 9 It has been suggested that this reaction might occur as a multiphase reaction (i.e. between CO2 and catalyst both dissolved in liquid 3-hexyne) and not in scCO2:
Dinjus E. COST/Dechema Workshop Lahnstein Germany: April 1995. - 10
Kreher U.Schebesta S.Walther D. Z. Anorg. Allg. Chem. 1998, 624: 602 - For safety data for P(CH3)3, see:
-
14a
Sigma-Aldrich Library of Chemical Safety Data
Vol. 2:
Lenga RE. Sigma-Aldrich Corp.; Milwaukee: 1995. p.3435C -
14b
Sigma-Aldrich Library of Regulatory & Safety Data
Vol. 1:
Lenga RE.Votoupal KL. Sigma-Aldrich Corp.; Milwaukee: 1993. p.1087E - 15 For safety data for P(C2H5)3, see:
Sigma-Aldrich Library of Regulatory & Safety Data
Vol. 1:
Lenga RE.Votoupal KL. Sigma-Aldrich Corp.; Milwaukee: 1993. p.1087C -
20a
Walther D.Bräunlich G.Kempe R.Sieler J. J. Organomet. Chem. 1992, 436: 109 -
20b
Hoberg H.Schaefer D.Burkhardt G.Kruger C.Romao M. J. Organomet. Chem. 1984, 266: 203 - 21
Bartik T.Himmler T.Schulte H.-G.Seevogel K. J. Organomet. Chem. 1984, 272: 29 - 22
Bodner GM.May MP.McKinney LE. Inorg. Chem. 1980, 19: 1951
References
Typical procedure for the Ni(0)-catalyzed cycloaddition of alkynes with CO 2 : All manipulations were carried out under a nitrogen or argon atmosphere. Alkyne 1a (2 mmol), phosphine 3b (0.4 mmol), and o-xylene (40 µL, internal standard for GC analysis) were mixed in a Schlenk tube. Ni(cod)2 (0.2 mmol) was placed in a stainless steel autoclave containing a magnetic stirring bar, and, to this, was added the above mixture via a dry syringe. CO2 (ca. 5 MPa) was quickly introduced, and the autoclave was immersed in an oil bath at 120 °C. When the temperature of the reactor reached the desired temperature (typically after about 10 min), more CO2 was added to achieve the desired pressure of 15 MPa. The time of the second addition of CO2 was considered to be the start of the reaction. The mixture was allowed to stir for 20 h. Then, the vessel was removed from the oil bath, immersed in an ice bath for ca. 1 h, and allowed to cool to ca. 0 °C. Excess CO2 was then slowly vented at ca. 0 °C. The remaining organic liquid was diluted with acetone. The GC analysis of the solution indicated the conversion of 1a and the yield of 2a were 100% and 95%, respectively. Acetone was removed by evaporation, and the residue was chromatographed on silica gel (hexanes-EtOAc, 15:1) to give analytically pure 2a in 91% isolated yield. The product was identified by 1H NMR and GC-MS analyses. The 1H NMR spectrum was identical to the spectral data reported in ref. 1a.
12CAUTION: Certain alkynes turn immediately brown when they are mixed with trialkylphosphines and the use of such alkynes does not give desired results. The reason for this is unclear at this time, but we recommend the use of the alkynes that cause no color change.
13The product yield was determined by GC analysis on the basis of the alkyne 1 employed. Thus, the yield (%) of 2-pyrone 2 = 100 × [(mmol of alkyne component in 2) / (mmol of 1)] = 100 × [(2 × mmol of 2) / (mmol of 1)]; and the yield (%) of alkyne trimer 4 or 5 = 100 × [(mmol of alkyne component in 4 or 5) / (mmol of 1)] = 100 × [(3 × mmol of 4 or 5) / (mmol of 1)].
The selectivity for 2 is defined as the mol% of 2 in all of the reaction products and is calculated from the yields of 2, 4, and 5 by using the above equations. Thus, the selectivity (%) for 2 = 100 × [(mmol of 2) / (mmol of 2 + mmol of 4 + mmol of 5)] = 100 × [(% yield of 2) / 2] / {[(% yield of 2) / 2] + [(% yield of 4) / 3] + [(% yield of 5) / 3]}.
16Selected data for compound 2c: 1H NMR (CDCl3, 270 MHz): δ = 2.36-2.49 (m, 6 H, CH2), 2.24-2.29 (t, J = 7.3 Hz, 2 H, CH2), 1.59-1.70 (m, 2 H, CH2), 1.30-1.45 (m, 14 H, CH2), 0.91-1.00 (m, 12 H, CH3). 13C NMR (CDCl3, 67.5 MHz): δ = 163.7 (C=O), 158.1 (Cvinyl), 154.5 (Cvinyl), 123.2 (Cvinyl), 115.4 (Cvinyl), 33.4 (CH2), 32.1 (CH2), 31.2 (CH2), 30.7 (CH2), 30.1 (CH2), 29.3 (CH2), 27.1 (CH2), 26.6 (CH2), 23.3 (CH2), 23.1 (CH2), 23.0 (CH2), 22.6 (CH2), 14.1 (CH3), 13.93 (CH3), 13.90 (CH3), 13.8 (CH3). HRMS (EI): m/z calcd for C21H36O2: 320.2715. Found: 320.2729.
17Through careful column chromatography on silica gel (hexanes-EtOAc, 30:1), analytically pure 2d′ could be isolated from the reaction mixture as a colorless oil (15 mg, 8%). 1H NMR (CDCl3, 270 MHz): δ = 2.54 (t, J = 7.6 Hz, 2 H, CH2), 2.53 (t, J = 7.6 Hz, 2 H, CH2), 2.09 (s, 3 H, CH3), 1.94 (s, 3 H, CH3), 1.19 (t, J = 7.6 Hz, 3 H, CH3), 1.07 (t, J = 7.6 Hz, 3 H, CH3). 13C NMR (CDCl3, 67.5 MHz): δ = 163.4 (C=O), 157.9 (Cvinyl), 150.8 (Cvinyl), 124.4 (Cvinyl), 110.8 (Cvinyl), 24.6 (CH2), 20.5 (CH2), 16.3 (CH3), 13.0 (CH3), 12.8 (CH3), 12.1 (CH3). 1H NMR: NOE enhancement (2.8%) between the methyl protons at 1.94 ppm and the methyl protons at 2.09 ppm was observed. HRMS (EI): m/z calcd for C11H16O2: 180.1146. Found: 180.1144.
18Selected data for compound 2e: 1H NMR (CDCl3, 270 MHz): δ = 4.47 (s, 2 H, CH2O), 4.45 (s, 2 H, CH2O), 4.37 (s, 2 H, CH2O), 4.33 (s, 2 H, CH2O), 3.42 (s, 3 H, CH3O), 3.41 (s, 3 H, CH3O), 3.40 (s, 3 H, CH3O), 3.37 (s, 3 H, CH3O). 13C NMR (CDCl3, 67.5 MHz): δ = 162.1 (C=O), 158.6 (Cvinyl), 152.1 (Cvinyl), 123.7 (Cvinyl), 115.4 (Cvinyl), 68.6 (CH2O), 67.0 (CH2O), 65.6 (CH2O), 65.1 (CH2O). HRMS (EI): m/z calcd for C13H20O6: 272.1260. Found: 272.1257.
19Selected data for compound 5e: 1H NMR (CDCl3, 270 MHz): δ = 4.60 (s, 12 H, CH2O), 3.41 (s, 18 H, CH3O). MS (EI): m/z (%) = 310 (38) [M+ - 32], 295 (100), 265 (42), 233 (30), 203 (23).