Electroreductive Intermolecular Coupling of Coumarins with Benzophenones: Synthesis of 4-(2-Hydroxyphenyl)-5,5-diaryl-γ-butyrolactones, 2-(2,2-Diaryl-2,3-dihydrobenzofuran-3-yl)acetic Acids, and 4-(Diarylmethyl)coumarins.