Polymeric Carbon Nitride-Photocatalyzed Aerobic Epoxidation of Alkenes: Application to a Sustainable Synthesis of Rose Oxide.

A urea-based pristine polymeric carbon nitride catalyzes the aerobic epoxidation of citronellol under visible light irradiation with low-power blue LEDs. Formation of 6,7-epoxycitronellol in this reaction is remarkably selective yet relatively slow requiring 72 h of continuous irradiation. The aerobic photocatalyzed epoxidation is readily accelerated with isobutyraldehyde as a comediator, and a general photocatalytic procedure for the epoxidation of terpenoid substrates as well as styrene derivatives is thus developed to give the corresponding epoxides in good yields within attractive reaction times. The carbon nitride-photocatalyzed aerobic epoxidation is demonstrated in 14 examples, and the epoxidation of citronellol enables a short and sustainable three-step synthesis of the industrially relevant terpenoid fragrance compound rose oxide.