Photochemical macrocyclization: synthesis of lactones, lactames, ethers and thioethers

The triplet-sensitized photodecarboxylation of w-phthalimido potassium carboxylates was developed as an efficient and chemoselective method for the formation of macrocyclic ring systems such as azacycloalkanes (2, 4), lactones (6, 8), cyclic ethers (10a), cyclic thioethers (10b-d), crown ethers (12), and lactames (14a-f). MTM-incorporated lactones (16a-b) and cyclodipeptides (18a-c) were synthesized by a similar concept using the thioether functionality as the electron donating group