Ir(III)-Catalyzed C-H Alkylation of Aryl Ketone and Chromanone under Mild Conditions; Two-Step Synthesis of Cytosporones B and N

An Ir(III)-catalyzed ortho-C-H alkylation of aryl ketones with diazo Meldrum's acid was developed for the synthesis of 2-(2-alkanoylaryl)acetate derivatives. The reaction took place under mild atmospheric conditions with broad substrate scope. Further, the developed catalytic system was found to be suitable for the selective C5-alkylation of flavanone and chromanone derivatives. Mechanistic studies revealed that the reaction proceeds via initial Ir(III)-catalyzed selective ortho-alkylation followed by decarboxylative esterification with the alcohol to furnish the final product. Notably, the developed reaction was successfully applied in the total synthesis of cytosporones B and N in two steps starting from resorcinol.