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In this work, the reactivities of acetonyl and benzoyl radicals in aromatic substitution and addition reactions have been compared in an experimental and computational study. The results show that acetonyl is more electrophilic than benzoyl, which is rather nucleophilic. A Hammett plot analysis of the addition reactions of the two radicals to substituted styrenes clearly support the nucleophilicity of benzoyl, but in the case of acetonyl, no satisfactory linear correlation with a single substituent‐related parameter was found. Computational calculations helped to rationalize this effect, and a good linear correlation was found with a combination of polar parameters (σ+) and the radical stabilization energies of the formed intermediates. Based on the calculated philicity indices for benzoyl and acetonyl, a quantitative comparison of these two radicals with many other reported radicals is possible, which may help to predict the reactivities of other aromatic radical substitution reactions. [ABSTRACT FROM AUTHOR]

Abstract: Alkenyl and aryl peroxides are a special class of organic peroxides. Under ambient conditions, they are usually short‐lived, rapidly decomposing into radicals by homolytic O−O bond cleavage. They play an important role in the chemistry of the lower atmosphere, where they are formed through ozonolysis of alkenes. In the dark, this pathway is considered the major source of hydroxyl radicals, the “detergent of the atmosphere”. In solution, alkenyl and aryl peroxides can be formed by various methods and their decomposition can be harnessed synthetically. For example, reactions involving alkenyl peroxides can be used to introduce ketones through radical additions, and nucleophilic aromatic substitution reactions generating aryl peroxides have been used to synthesize phenols. The radicals can also initiate radical polymerization reactions or chain reactions and mediate oxidative coupling by C−H bond functionalization. Knowledge of their chemistry could be helpful for projects generating or utilizing peroxides. [ABSTRACT FROM AUTHOR]

This account summarizes how scientific advances were made in the authors' research group by combining method development in organic synthesis with detailed mechanistic studies. The discovery of an unexpected autoxidative coupling reaction led, by virtue of an ever increased understanding of its mechanism, to a strategy for green C-H functionalization reactions, novel modes of radical generation, addition reactions of ketones to alkenes and new insights into an old reaction, the Baeyer-Villiger oxidation. [ABSTRACT FROM AUTHOR]

Oxindoles bearing ketone side chains in the 3-position can be synthesized by Brønsted acid catalysis from N-aryl methacrylamides, ketones, and hydroperoxides. The cyclized products are presumably formed in a radical cascade reaction, initiated by decay of intermediate alkenyl peroxides. In the case of acrylic substrates that do not undergo cyclization, γ-peroxyketones were isolated instead, indicating that the final cyclization step of the cascade does not take place in these cases. [ABSTRACT FROM AUTHOR]

Based on a mechanistic study, we have discovered a Brønsted acid catalyzed formation of ketone radicals. This is believed to proceed via thermally labile alkenyl peroxides formed in situ from ketones and hydroperoxides. The discovery could be utilized to develop a multicomponent radical addition of unactivated ketones and tert-butyl hydroperoxide to olefins. The resulting γ-peroxyketones are synthetically useful intermediates that can be further transformed into 1,4-diketones, homoaldol products, and alkyl ketones. A one-pot reaction yielding a pharmaceutically active pyrrole is also described. [ABSTRACT FROM AUTHOR]