Mechanistic Insights into Cyclopropenes-Involved Carbonylative Carbocyclization Catalyzed by Rh(I) Catalyst: A DFT Study

Abstract

Computational studies were carried out to provide mechanistic insights into the Rh­(I)-catalyzed activation of cyclopropenes and the detailed mechanistic pathways of [3+2+1] carbonylative carbocyclization of tethered ene- and yne-cyclopropenes. Computational results suggest that it is more favorable for the cyclopropene moiety of tethered ene-cyclopropenes to initially undergo heterolytic cleavage of a C–C σ-bond to form a vinyl Rh­(I) carbenoid intermediate than to proceed through homolytic C–C σ-bond cleavage to generate a rhodacyclobutene intermediate. The yielded vinyl Rh­(I) carbenoid intermediate could undergo cyclization to generate a Rh­(III) metallacyclobutene intermediate, which could further lead to a thermodynamically more stable six-coordinated Rh­(III) metallacycle intermediate in the presence of additional CO. Afterward, it is more feasible for the yielded six-coordinated Rh­(III) metallacycle to sequentially undergo CO migratory insertion, cyclization, and reductive elimination to furnish the final cyclohexenone product. The origin of stereoselectivity of the product was also discussed. The proposed mechanistic pathway can also be applied to the Rh­(I)-catalyzed carbonylative carbocyclization of tethered yne-cyclopropenes and vinyl cyclopropenes to produce phenol derivatives. The main mechanistic difference for the vinyl cyclopropene substrate is that the conversion of Rh­(I) carbenoid intermediate to the Rh­(III) metallacycle proceeds via intramolecular 6π electrocyclization.

C–C Bond Cleavages of Cyclopropenes: Operating for Selective Ring-Opening Reactions

“…Subsequent computational studies indicated the need to consider the participation of a rhodium carbene intermediate generated from cyclopropene σ-C−C bond cleavage. 174 Noticeably, the reaction with cyclopropene-ene derivatives was also included in this work, leading in this case to structurally related bicyclic ketones.…”

“…276,277 In recent years, Wang and co-workers studied the reactivity of 1,n-cyclopropene-enes and -ynes in the presence of CO in the context of rhodium-catalyzed carbonylative cycloisomerization reactions of enynes (see Section 7, Scheme 37B). 174 Interestingly, 3-(amidomethyl)-and similar cyclopropenes 401 showing the C−C double bond of cyclopropene as single unsaturated moiety, also underwent rhodium-catalyzed carbonylation reactions providing cyclobutenone derivatives 402 (Scheme 61). 278 This transformation comprises a regioselective insertion of CO into a σ-C−C bond of the starting cyclopropene.…”

“…However, it seems reasonable to assume the participation of rhodacyclic intermediates similar to those indicated in Scheme C, with the insertion of CO in one of those steps. Subsequent computational studies indicated the need to consider the participation of a rhodium carbene intermediate generated from cyclopropene σ-C–C bond cleavage . Noticeably, the reaction with cyclopropene-ene derivatives was also included in this work, leading in this case to structurally related bicyclic ketones.…”

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

“…Rhodium salts coordinated with proper ligands have been reported to be able to realize the activation of CO and H 2 and thus might achieve the reductive carbonylation of aryl iodides to afford aromatic aldehydes [37][38][39][40]. Rh salts generally play vital roles in the catalytic results.…”

Mechanistic Insights into the Rh(I)/Rh2(II)‐Catalyzed Divergent Ring‐Opening of Cyclopropenes: A Computational Study

“…[15a] The mechanisms of gold(I)-catalyzed rearrangement of cyclopropenes were also investigated by computational studies. [16] In continuing our research interest on the mechanistic studies of highly strained molecules involved reactions, [17] herein, computational studies were carried out to explore the mechanisms of Rh(I)-and Rh 2 (II)-catalyzed regio-selective transformation of allylic cyclopropenecarboxylates (1) to produce Δ β,γ butenolides 2 and 3, respectively. The different mechanisms for the Rh(I) and Rh 2 (II)-catalyzed ring-opening of 1 are disclosed and the origins of the different regioselectivities are revealed in this work.…”