σ-Bond Migration Assisted Decarboxylative Activation of Vinylene Carbonate in Rh-Catalyzed 4 + 2 Annulation: A Theoretical Study

Abstract

As a C2 synthon, vinylene carbonate has been used instead of acetylene in transition-metal catalyzed-coupling reactions. In this study, the mechanism of the vinylene carbonate activation mode for the Rh­(III)-catalyzed 4 + 2 annulation of benzamide and vinylene carbonate reaction is proposed, and it was investigated by DFT with the M06 density functional. The computational results show that the proposed reaction pathway, which includes the insertion of vinylene carbonate into an Rh–C bond, decarboxylation of the seven-membered rhodacycle intermediate, protonation of the ketonate rhodium intermediate, deprotonation of the benzamide, and catalyst regeneration, is the most favorable pathway. The 1,2-rhodium migration process can assist decarboxylative activation of vinylene carbonate, which is the rate-determining step in the catalytic cycle. The IRC calculation clearly revealed a quasi-synchronized process to directly afford a cyclic ketonate rhodium intermediate by the release of carbon dioxide.

Synthesis of Substituted 1‐Hydroxy‐2‐Naphthaldehydes by Rhodium‐Catalyzed C−H Bond Activation and Vinylene Transfer of Enaminones with Vinylene Carbonate

“…as well as the group of Wang and Zhou, [8b–d] β ‐oxygen elimination and decarboxylation of the rhodacycle intermediate B generates the alkoxide intermediate C (path a). However, according to the recent theoretical study of Bai and Lan's group, [8i] it is also possible that rhodacycle intermediate B undergoes 1,2‐rhodium shift and decarboxylation generates the intermediate C’ (path b). Here, it is difficult for us to rule out either of these two paths.…”

Computational Study on Mechanisms and Origins of Selectivities in Rh(I)-Catalyzed Cycloisomerizations of 1,6-Allenynes with Tethered Unsaturated Carbon–Carbon Bonds

“…The single-point energies were computed at the M06 , level of theory with the SDD basis set − for rhodium and the 6-311+G­(d,p) basis set for other atoms. The combination of B3LYP with M06 has been widely applied in the computational study of rhodium-catalyzed reactions. − The solvation energies were evaluated with the SMD model using 1,4-dioxane as the solvent. All reported energies of intermediates and transition states are solvated Gibbs free energies.…”

Assembly of the Hydroxycinnoline Core via Hydrazide-Assisted Rh(III)-Catalyzed C–H Functionalization and Annulation

“…Coordination of vinylene carbonate (2a) followed by migratory insertion can furnish a seven-membered N-Rh(III)-C species B. Subsequently, 1,2-Rh−C bond migration occurs along with the release of CO2 to deliver the ring-contracted rhodacycle C. 17 Depending on the reaction conditions (see Table 1), olefinated adduct 3aa can be formed by dehydration reaction of 3a.…”

“…the seven-membered N-Rh(III)-C species B. Subsequently, 1,2-Rh-C bond migration occurs along with the release of CO 2 to deliver the ring-contracted rhodacycle C. 18 Then, protonation takes place for the formation of acetaldehyde intermediate D, which rapidly undergoes the annulation reaction to provide hydroxycinnoline 3a. Depending on the reaction conditions (see Table 1), olefinated adduct 3aa can be formed by a dehydration reaction of 3a.…”