Mechanistic insights into rhodium-catalyzed enantioselective allylic alkylation for quaternary stereogenic centers

Abstract

The origin of high enantioselectivity in the formation of quaternary stereogenic carbon.

The Role of Xantphos in forming an Elusive dirhodium-η1-allyl Intermediate in a Rh(II)-Catalyzed Allylic Alkylation: A Combined Computational and Experimental Study

“…However, numerous attempts to locate the transition states for both the SN2′-like and reductive elimination pathways were unsuccessful. A previous DFT study by Sunoj and co-workers 30 indicates a nearly barrierless allylic alkylation transition state from a rhodiumη 3 -allyl intermediate. We attempted to generate the potential energy surface for the SN2′-like process using a reduced system (acetate in place of octanoate and two trimethyl phosphine molecules in place of Xantphos), but no saddle point was seen in the relaxed energy scan (Figure 8), indicating a nearly barrierless transition state for this reaction.…”

The Role of Xantphos in forming an Elusive dirhodium-η1-allyl Intermediate in a Rh(II)-Catalyzed Allylic Alkylation: A Combined Computational and Experimental Study

“…However, numerous attempts to locate the transition states for both the SN2′-like and reductive elimination pathways were unsuccessful. A previous DFT study by Sunoj and co-workers 25 indicates a nearly barrierless allylic alkylation transition state from a rhodium-η 3 -allyl intermediate. We attempted to generate the potential energy surface for the SN2′-like pathway using a reduced system (acetate in place of octanoate and two trimethyl phosphine molecules in place of Xantphos), but no saddle point was seen in the relaxed energy scan (Figure 8), indicating a nearly barrierless transition state for this reaction.…”

A computational study on cobalt-catalyzed allylic substitution of racemic allylic carbonates with amines: inner-sphere C–N reductive elimination and origins of regio- and enantioselectivities

“…Given the significance of the transition metal-catalyzed allylic substitution reactions, the mechanistic understandings have been extensively studied both experimentally 13 and theoretically. [14][15][16][17] However, the majority of these studies have been focused on reactions catalyzed by palladium, 14 iridium, 15 and rhodium complexes, 16 while the reactions catalyzed by the first-row transition metals have been rarely explored. 17 Considering that the detailed reaction mechanism and the origins of the regio-and enantioselectivities remain unclear, we herein report a comprehensive mechanistic study of the title reaction by means of density functional theory (DFT) calculations.…”