Partially fluorinated heterocycles from 4,4-bis(trifluoromethyl)-hetero-1, 3-dienes via C-F bond activation - Synthesis of 2-fluoro-3-(trifluoromethyl) furans

An efficient synthesis of 2-fluoro-3-(trifluoromethyl)furans was developed. Keystep of the reaction sequence is a [4 + 1] cycloaddition reaction of tin(II)chloride to 4,4-bis(trifluoromethyl)-1-oxabuta-1,3-dienes. At elevated temperatures the tin heterocycles are transformed into 1-aryl-4,4-difluoro-3- (trifluoromethyl)but-3-en-1-ones which on treatment with sodium hydride in dry DMF give 2-fluoro-3-(trifluoromethyl)furans. The single fluorine bound to C-(2) can be readily replaced by various N-, O-, S-, and C-nucleophiles and dinucleophiles.