DFT investigation on mechanism of dirhodium tetracarboxylate-catalyzed O-H insertion of diazo compounds with H2O

Abstract

Abstract:The mechanism of the dirhodium tetracarboxylate-catalyzed O-H insertion reaction of diazomethane and methyl diazoacetate with H 2 O has been studied in detail using DFT calculations. The rhodium catalyst and a diazo compound couple to form a rhodiumcarbene complex. Of two reaction pathways of the Rh(II)-carbene complex with H 2 O, the stepwise pathway is more preferable than the concerted one. Formation of a Rh(II) complex-associated oxonium ylide is an exothermal process, and direct decomposition of the ylide gives a very high barrier. The high barriers for the 1,2-H shift of Rh(II) complex-associated oxonium ylides make the ylides become stable intermediates in both reactions, especially for the reactions in solution. Difficulty in formation of a free oxonium ylide supports experimental results, indicating that the Rh(II) complex-catalyzed nucleophilic addition of a diazo compound proceeds via a Rh(II) complex-associated oxonium ylide rather than via a free oxonium ylide.

Cooperative Catalysis of Chiral Guanidine and Rh2(OAc)4 in Asymmetric O–H Insertion of Carboxylic Acid: A Theoretical Investigation

“…The sterically bulkier acids could improve the diastereoselectivity, and the electron-donating ligand made the electrophilic carbene species less reactive and thus more selective . Liu, Z. and Liu, J. studied theoretically the mechanism of the dirhodium tetracarboxylate-catalyzed O–H bond insertion reactions of diazomethane and methyl diazoacetate with water . They proposed that the nucleophilic addition proceeded via a Rh­(II)-complex-associated oxonium ylide (not a free oxonium ylide).…”

“…7 Liu, Z. and Liu, J. studied theoretically the mechanism of the dirhodium tetracarboxylate-catalyzed O−H bond insertion reactions of diazomethane and methyl diazoacetate with water. 19 They proposed that the nucleophilic addition proceeded via a Rh(II)-complex-associated oxonium ylide (not a free oxonium ylide). The computational study by Yu's group suggested that in neutral dirhodium(II) complexcatalyzed O−H bond insertion, a free-ylide pathway was facilitated, and H 2 O could accelerate the [1,2]-H shift as an proton shuttle.…”