Photooxidation of N-acylhydrazones to 1,3,4-oxadiazoles catalyzed by heterogeneous visible-light-active carbon nitride semiconductor

Abstract

Highlights • Potassium poly(heptazine imide) is used as a visible light photocatalyst; • Photocatalytic synthesis of substituted 1,3,4-oxadiazoles; • Sulfur is used as highly selective electron scavenger; • The photocatalytic reaction proceeds through proton coupled electron transfer

Photoredox Catalytic Organic Transformations using Heterogeneous Carbon Nitrides

“…The same catalytic system was also shown to be highly efficient in synthesizing various substituted oxadizoles from their corresponding hydrazones via a photoredox catalytic oxidative cyclization reaction (Scheme 20). [58] Here, elemental sulfur was used again as a more selective electron acceptor, compared to O 2 , furnishing substituted oxadiazoles in high yields. Savateev et al also reported the synthesis of various thioamides using primary or secondary amines, elemental sulfur and K-PHI as a heterogeneous photocatalyst under visible light irradiation (Scheme 21).…”

Ionic Carbon Nitrides in Solar Hydrogen Production and Organic Synthesis: Exciting Chemistry and Economic Advantages

“…K‐PHI is a convenient photocatalyst to trigger dehydrogenation reactions. This feature has been employed in oxidative cyclization of N ‐alkylidene hydrazones to 1,3,4‐oxadiazoles (Scheme ) . The method works excellent when S 8 was used as electron acceptor.…”

A “waiting” carbon nitride radical anion: a charge storage material and key intermediate in direct C–H thiolation of methylarenes using elemental sulfur as the “S”-source

“…Due to the highly positive valence band (VB) potential, +2.22 V vs. NHE, photogenerated holes are effective oxidants for application in organic synthesis. For example, K-PHI was successfully used in the oxidation of alcohols to aldehydes and 1,4-dihydropyridines to pyridines, 18 in the synthesis of 1,3,4-oxadizoles by oxidative cyclization of N -acylhydrazones, 19 in thioamide synthesis by photocatalytic Kindler reaction, 20 and in oxygen and hydrogen evolution reactions. 21 …”