[70]Fullerene-fused lactones: synthesis, conversion and photovoltaic application

Syntheses of [70]fullerene-fused lactones <i>via</i> palladium-catalysed annulation and 1,4-dipolar cycloaddition with complementary regioselectivities were achieved. Efficient retro Baeyer-Villiger reaction <i>via</i> electroreduction and trifluoromethanesulfonic anhydride treatment afforded [70]fullerene-fused ketones. Control experiments and theoretical calculations elucidated plausible reaction pathways. Representative products improved the organic photovoltaic efficiency to 18.27%.