Aggregation‐induced Substrate Specificity in Aerobic Reduction of Olefins with Ultrasound Gel Catalyst of Synthetic Flavin

A riboflavin derivative bearing octadecanoyl functionalities 1 a gelatinizes a variety of organic solvents upon brief ultrasonication in an organic fluid. The rate of gelation with 1 a can be externally and precisely controlled by tuning the sonication time and type of solvent. The present ultrasound gel exhibits unprecedented substrate specificity for the catalytic aerobic reduction of olefins, which can be performed with hydrazine at ambient temperature and atmospheric pressure in air. The reaction rates of 1‐dodecene ( 2 ), allylbenzene ( 3 ), and o ‐allylphenol ( 4 ) with the ultrasound gel 1 a catalyst is in the order of 2 ≫ 3 > 4 , the substrate specificity of which is in contrast to the almost non‐specificity with the non‐gelled catalyst 1 b bearing butanoyl functionalities, and entirely inverse specificity with a flavin‐dendrimer association catalyst ( 2 < 3 < 4 ). Based on kinetic studies, the aggregation effects on the substrate specificity have been ascribed to the specific inclusion of aliphatic olefins into the enzyme‐like artificial cavities of the gel catalysts.