Initially the perfluoroacylation of a range of commercially available vinyl ethers and conversion of the resulting perfluoroacylated enol ethers to 1-H-pyrazoles via reaction with hydrazine is reported. The selective synthesis of a range of alpha-aryl vinyl ethers using Heck chemistry is then reported. Subsequent perfluoroacylations of the vinyl ethers followed by reaction of the resulting perfluoroacyl enol ethers with hydrazine affords a range of 5-aryl-3-perfluoroalkyl pyrazoles in good yields.;Alternative methodology for the synthesis of 5-aryl-3-perfluoroalkyl pyrazoles is then described in which resin bound esters are converted to vinyl ethers <via a Tebbe reaction. Subsequent perfluoroacylations generate the expected resin bound perfluoroacyl enol ethers and cleavage with cyclisation with hydrazine liberates the desired pyrazoles in acceptable yields for this type of methodology. Finally the microwave mediated Suzuki coupling of 4-iodo-1-methyl-3-trifluoromethyl-1-H-pyrazole with various boronic acids is reported as a general way in which 4-substituted-3-perfluoroalkyl-pyrazoles can be synthesised rapidly in reasonable yields.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:412813 |
| Date | January 2004 |
| Creators | Oleksik, Laurence |
| Publisher | University of Leicester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2381/30087 |
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