1-Bromo-2-trifluoroacetylcyclobutenes as novel building blocks for the construction of trifluoromethyl substituted heterocycles. Part 1: Synthesis of 5-(trifluoromethyl)-2(5H)-furanones condensed with substituted cyclobutenes

The regioselective reduction of substituted 1-bromo-2-trifluoroacetylcyclobutenes by lithium aluminium hydride affords corresponding brominated alcohols, which, under the treatment of two equivalents of butyllithium, give new lithiated cyclobutenes. Their carboxylation followed by lactonization induced by trifluoroacetic anhydride appeared to be an effective approach towards 5-trifluoromethylated furanones condensed with substituted cyclobutene rings.