Oxidative Addition Promoted C–C Bond Cleavage in Rh-Mediated Cyclopropenone Activation: A DFT Study

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.

Rh(iii)-Catalyzed spiroannulation of ketimines with cyclopropenonesviasequential C–H/C–C bond activation

“…However, the pathway of ring-opening of cyclopropenones via C–C bond oxidative addition for accessing intermediate IV could not be excluded. 14 Finally, nucleophilic addition of the C–Rh bond to the ketimine followed by protonation gives rise to the desired spirolactam 3aa , and releases the active Rh( iii ) to continue the catalytic cycle.…”

Three-Component Couplings among Heteroarenes, Difluorocyclopropenes, and Water via C–H Activation

“…On the basis of the results presented above and previous reports, 37,48 plausible reaction mechanisms are presented in Scheme 7. Initially, the cyclopropenone is formed from difluorocyclopropene 2a in the presence of water.…”

Mechanistic differences between aryl iodide electrophiles and pronucleophiles in Pd-catalyzed coupling with cyclopropenes: a DFT study

“…Mechanistic studies of the transition-metal-catalyzed ring-opening reactions of cyclopropenes have attracted substantial research interest. 5,10 For example, Xia et al 10 a conducted a DFT study to understand the mechanism of Rh( iii )-catalyzed C–H activation reactions of N -phenoxyacetamide and N -pivaloxybenzamide with cyclopropenes and indicated that the seven-membered rhodacycle from the migratory insertion of cyclopropene was crucial for both reactions. In addition, Lan and co-workers 10 f computationally studied the ring-opening of cyclopropenone in rhodium-catalyzed cyclopropenone conversion via quinolyl-, pyridyl-, and nitrone-directed C–H activation.…”