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Article
Selectivity of 1,3-Dipolar Cycloaddition of Methyl Propiolate to 3-Phenylsyndone in Supercritical Carbon Dioxide
Journal of Supercritical Fluids
  • H. Totoe
  • Audrey E. McGowin, Ph.D., Wright State University - Main Campus
  • Kenneth Turnbull, Wright State University - Main Campus
Document Type
Article
Publication Date
9-10-2000
Identifier/URL
http://www.journals.elsevier.com/the-journal-of-supercritical-fluids/
Abstract
The selectivity of the 1,3-dipolar cycloaddition reaction of methyl propiolate to 3-phenylsydnone was measured under various conditions of pressure (7.6–30.4 MPa) and temperature (333–423 K) in near- or supercritical carbon dioxide. The reaction produces a mixture of two regioisomers, 3-carbomethoxy-1-phenylpyrazole (isomer A) and 4-carbomethoxy-1-phenylpyrazole (isomer B). Reaction composition was measured by high-performance liquid chromatography (HPLC). A supercritical fluid extraction (SFE) instrument, programmed in the static mode, was used as the reaction apparatus. The selectivity (isomer A:isomer B) of the reaction was compared with the selectivity in toluene at 353 K. For both solvents, selectivity did not vary over time for up to 12 h in CO2 and 67 h in toluene. The mean selectivity measured in toluene was 3.62 compared with 5.08 in CO2. At 7.6 MPa and 1 h in CO2, the selectivity decreased with increasing temperature from 5.52 at 353 K to 3.14 at 423 K. At 353 K and 3 h, the selectivity increased with increasing pressure from 4.96 at 7.6 MPa to 6.56 at 30.4 MPa, however, the yield decreased by 50%. Overall, lower pressure and higher temperature gave higher yields while higher pressure and lower temperature produced greater selectivity of isomer A over isomer B.
Citation Information
H. Totoe, Audrey E. McGowin and Kenneth Turnbull. "Selectivity of 1,3-Dipolar Cycloaddition of Methyl Propiolate to 3-Phenylsyndone in Supercritical Carbon Dioxide" Journal of Supercritical Fluids Vol. 18 Iss. 2 (2000) p. 131 - 140 ISSN: 0896-8446
Available at: http://works.bepress.com/audrey_mcgowin/50/