Novel Synthetic Methodology Utilizing Fluorous Phases as a Liquid Screen

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In this project, we studied "the Phase-Vanishing(PV) Method". This novel method that we developed recently utilizes unique properties of the fluorous phase. The PV method, which capitalizes on the diffusion of reagents through the fluorous phase, is very simple methodology, and does not need any dropping funnels, heating/cooling baths, and thermometers. Inspection of suitable solvent for the PV method reveals that FC-72(perfluorohexanes) is an outstanding fluorous solvent. Firstly we examined bromination of olefins with Br2 ; this reaction finished in 2 days with standing to afford corresponding dibromide in 68-97% yields, while gentle stirring of the bromine layer, taking care not to mix the three layers, the reaction completed in 4 hours giving similar yields (88-91%). We also carried out various organic reactions including demethylations of aryl methyl ethers with BBr_3, bromination of alcohols with PBr_3 or SOBr_3, and the Friedel-Crafts acylations of aromatic compounds with SnCl_4 using the PV method, and showed that the method gave corresponding products in good yields. A parallel synthesis of the PV method in the Friedel-Crafts acylations using a very simple multi-fingered glass apparatus is also performed successfully, providing four types of aromatic keteones in high yield (64-85%) at once. During this project with FC-72 we have found that the solvent has weak points. Namely, the recovery of FC-72 is invaluably incomplete due to its high volatility, and in the parallel synthesis we sometimes faced contamination of products. In order to overcome these problems, we searched again more suitable fluorous solvents for the PV method than FC-72, and found that perfluoropolyethers (Galden) are a superior solvent.