Riboflavin Photocatalyzed Dearomative Spiro-Etherification of Naphthols

Abstract

The dearomative spiro-etherification of naphthols is achieved using catalytic amounts of riboflavin tetracetate (RFTA) as a photosensitizer and molecular oxygen as a terminal oxidizing agent under blue light (440 nm) irradiation in the presence of acid. The presence of acid increases the photooxidation power of RFTA and facilitates the dearomatization reaction.

Metal- and base-free, aerobic photoredox catalysis with riboflavin to synthesize 2-substituted benzothiazoles

“…In order to recover the photocatalyst, RFTA-H 2 is oxidized by oxygen generating hydrogen peroxide (H 2 O 2 ) as a by-product. 55 The presence of H 2 O 2 was evidenced by a positive result for the formation of species I 3 − with the iodide/starch test on the aqueous phase at the end of the reaction (see procedure and relevant pictures in ESI†).…”