An efficient and convergent (4+1)-cycloaddition strategy toward the construction of spirooxindole benzofurans that involves the intermediacy of an isatin-derived oxyphosphonium enolate is presented. Mechanistic investigations employing in situ NMR analysis of the reaction mixture revealed a correlation between phosphonium enolate structure and product distribution that was heavily influenced by the solvent and reaction temperature.
Keywords: cycloaddition; dihydrobenzofurans; ortho-quinone methides; oxindoles; oxyphosphonium enolates.
© 2021 Wiley-VCH GmbH.