Unusual condensation of 1,1,1,5,5,5-hexafluoropentane-2,4-dione with (R)-phenylglycinol

The reaction of 1,1,1,5,5,5-hexafluoropentane-2,4-dione with (R)-phenylglycinol proceeds via the intermediate formation of (R,4E,6Z)-5,7-bis(trifluoromethyl)-2,3-dihydro-3-phenyl-1,4-oxazepine, which further undergoes a base-catalysed 1,3-proton shift followed by [1,2] Wittig rearrangement giving rise to 2,4-bis(trifluoromethyl)-6-phenylpyridine.