Decarboxylative Intramolecular Cyclization and Sequential Halogenation of Cyclic Enol Carbonates ®Synthesis of Stereochemically-defined Seven-membered Carbocycles®

The intramolecular cyclization for the construction of 7-membered carbocycles triggered by the decarboxylation of a cyclic enol carbonate was studied. In this study, it was found that the treatment of the alkene-tethered cyclic enol carbonate with a metal halide resulted in the decarboxylation and sequential intramolecular cyclization, followed by halogenation to give a functionalized 7-membered ketone with high stereoselectivity. Among the Lewis acidic metal halides, titanium tetrachloride was the most effective for this transformation. This method was applicable for a variety of substrates.