Abstract
Computational characterization of the oxidation addition promoted in rhodium-catalyzed cyclopropenone activation and conversion via quinolyl-, pyridyl-, and nitrone-directed C–H activation is presented. Our theoretical studies found that a common catalytic cycle for these reactions starts with Rh(III)-mediated concerted metalation–deprotonation or electrophilic deprotonation to afford the aryl-Rh(III) intermediate. Oxidative addition of cyclopropenone to aryl-Rh(III) then gives a cyclorhoda(V)butanone intermediate, leading to the cleavage of the cyclopropene moiety through a concerted three-membered cyclic transition state. Subsequent reductive elimination of the intermediate generates a target C(aryl)–C(acyl) bond. The final product is produced by further transformations with concomitant regeneration of active Rh(III) catalyst. The previously proposed carbonyl insertion mode for the activation of cyclopropenones is excluded by the density functional theory calculations. The directing group effect in cyclopropenone activation was theoretically investigated. Distortion–interaction analysis, noncovalent interaction analysis, and global electrophilicity/nucleophilicity index calculations reveal the lower oxidation addition reactivity with the nitrone directing group, which is coincident with experimental observations. Distortion–interaction analysis was also performed to reveal the regioselectivity of the oxidative addition with asymmetrical cyclopropenones.
Published Version
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