Photoinduced electron transfer cyclizations of aryl-linked phthalimides

The photochemistry of arene-linked phthalimides incorporating the carboxylate or thioether donor group was investigated. Simple N-phthalimidophenyl alkanoates exclusively gave photoreduction (CO2H/H-exchange) products. In contrast, ω-phthalimido-meta-phenoxy carboxylates underwent photodecarboxylative cyclizations in yields of 6–48%. Likewise, catechol-linked derivatives furnished analogue cyclization products in 18–38% yield. Using the photodecarboxylation protocol, macrocyclic target compounds with ring sizes up to 17 could thus be realized. Two model phthalimides containing a thioether branch at the ortho-position of the arene-linker gave the analogue seven-membered cyclization products in yields of 28% and 35%, respectively.