Synthesis of Polysubstituted Benzoic Esters from 1,2-Dihydropyridines: Application to the Synthesis of Fluorenones

Abstract

In the last few years, we have been studying the propargyl Claisen rearrangement of propargyl vinyl ethers (PVEs). For example, PVEs may rearrange to valuable salicylaldehyde derivatives or 1,2-dihydropyridines depending on the reaction conditions.[1] During the course of this research we observed in certain occasions small amounts of benzoic ester side product. Because the importance of benzoic esters in various fields of organic chemistry, we decided to undertake the study of this transformation. Thus, a convenient methodology to transform 1,2-dihydropyridines into polysubstituted benzoic esters is described.[2] The products obtained feature different topologies spanning from simple aromatic rings to fused benzo-cycloalkanes systems. As an extension of this methodology, we also report the synthesis of polysubstituted fluorenones featuring interesting topological patterns.