The research focuses on the alkylidenation of esters on solid support and the traceless synthesis of 2-substituted benzofurans. The experiments involve the conversion of polymer-supported esters into enol ethers using a titanocene alkylidene, which is prepared by treating 2-tert-butyldimethylsilyloxybenzaldehyde diphenyldithioacetal with a low valent titanium species, Cp2Ti[P(OEt)3]2. The enol ethers are then treated with acid to release ketones from the Wang resin with high yield. A three-step termination procedure is used to achieve the traceless solid-phase synthesis of 2-substituted benzofurans. The reactants include titanocene dichloride, triethylphosphite, thioacetal, and Wang resin-bound esters, among others. Analytical techniques used to monitor the progress and confirm the completion of reactions include infrared (IR) spectroscopy for carbonyl absorption and weight gain measurements. The study demonstrates a novel alkylidenating agent that enables cyclative termination of solid-phase synthesis without leaving any trace of the attachment site on the solid support, which is beneficial for agrochemical and pharmaceutical research.
