Computational chemical analysis of Ru(II)‐Pheox–catalyzed highly enantioselective intramolecular cyclopropanation reactions

Abstract

Computational chemical analysis of Ru(II)‐Pheox–catalyzed highly enantioselective intramolecular cyclopropanation reactions was performed using density functional theory (DFT). In this study, cyclopropane ring–fused γ‐lactones, which are 5.8 kcal/mol more stable than the corresponding minor enantiomer, are obtained as the major product. The results of the calculations suggest that the enantioselectivity of the Ru(II)‐Pheox–catalyzed intramolecular cyclopropanation reaction is affected by the energy differences between the starting structures 5l and 5i. The reaction pathway was found to be a stepwise mechanism that proceeds through the formation of a metallacyclobutane intermediate. This is the first example of a computational chemical analysis of enantioselective control in an intramolecular carbene‐transfer reaction using C1‐symmetric catalysts.

Chiral Cyclometalated Oxazoline Gold(III) Complex-Catalyzed Asymmetric Carboalkoxylation of Alkynes

“…In this work, the enantioselectivity could be increased from 19% ee to 90% ee by simply increasing the steric size of the substituent on the C 1 -symmetric chiral oxazoline ligand, which is in line with the proposed species in Scheme d. Compared with C 2 -symmetric pybox ligands, examples of a C 1 -symmetric phenyl oxazoline ligand achieving a high enantioselectivity have been infrequently reported . Our work demonstrated the great potential of chiral gold­(III) complexes in asymmetric catalysis that comes from the short distance between substrates and chiral ligands in a square-planar geometry.…”

Combined Experimental and Computational Study of Ruthenium N-Hydroxyphthalimidoyl Carbenes in Alkene Cyclopropanation Reactions

“… 11 , 13 Mechanistic studies on simpler catalysts of the Ru-Pheox type are, however, still rather scarce. 14 While previously studied copper 7 and rhodium 8 catalysts have only one or two coordination sites available, the situation is greatly complicated in the case of Ru-Pheox ( 2 ) due to its octahedral C 1 -symmetric environment with four inequivalent positions that could lead to different intermediates (see Scheme 1 A).…”

“…The outer-sphere mechanism, on the other hand, involves intermolecular reaction with the olefin either in a single step or via radical intermediates . More recent computational work has focused on catalysts that promote the outer-sphere mechanism, employing bulky ligands or dimeric metal species. , Mechanistic studies on simpler catalysts of the Ru-Pheox type are, however, still rather scarce . While previously studied copper and rhodium catalysts have only one or two coordination sites available, the situation is greatly complicated in the case of Ru-Pheox ( 2 ) due to its octahedral C 1 -symmetric environment with four inequivalent positions that could lead to different intermediates (see Scheme A).…”

Regio- and Enantioselective Intramolecular Amide Carbene Insertion into Primary C–H Bonds Using Ru(II)-Pheox Catalyst

“…Therefore, the selective carbene insertion into unactivated primary C–H bonds remains a challenging research theme . Recently, we reported highly efficient transition metal carbene transfer catalysts and their applications for the synthesis of optically active cyclopropane derivatives in high yields with high stereoselectivities . Furthermore, we demonstrated transition metal-catalyzed N–H and Si–H insertion reactions of carbenes to construct N–C and Si–C bonds having chiral centers at the carbon and silicon atoms .…”