5-Trifluoromethyl Oxazole

The methods which substitute fluorine for proton at an aimed position in chemicals has an ability to convert into useful pharmaceuticals or functional materials due to fluorine specific potency, and is often used as one of the improvement means. Whereas compounds possessing 2-phenyl-5-methyl oxazole in a structure are known to quite a few, the papers related to 2-phenyl-5-trifluoromethyl oxazole of which substituted trifluoromethyl group instead of a methyl group as a partial structure are not so many.
For instance, it has been reported that the 5-trifluoromethylated oxazole part was constructed by Dakin-West reaction1) with TFAA or was synthesized by an introduction of the leaving group at 5-position of oxazole, following by substituted reaction

In addition, methyl ether (**) can be generated as cis- and trans- isomers, but was isolated as a single isomer. This compound was stable against heat at 60 degrees and was not transformed into 5-trifluoromethyl oxazole (**), whereas compound (*) was unstable, turned into easily rearrangement oxazole (**) in the middle of isolation. To confirm this rearrangement of compound (*), when we heated at 60 degrees for 30min, the compound (*) was observed to convert into oxazole (**)

If these unstable precursors were isolated as yilde forms, it was assumed that the value of δC of the 13CNMR chemical shift on C2-position of precursors would indicate near a value of benzo nitrile whose δC at nitrile carbon is about 120 ppm. However, δC of C2-position of the precursors were about 151 ppm. Rather, δC of C2- and C5-position of the precursors showed near a value of the chemical shift in comparison with starting materials. Furthermore, characteristic absorption peak of nitrile was not observed in IR spectral, but we viewed absorption one peak of near about 1700 cmm-1 derived from carbonyl