Asymmetric Acid Organocatalysis

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

“…3). This reaction was found to take place from methoxide-coordinated η 1 -allyl-Co( iii ) species IM6 triplet and IM6′ triplet , which can interconvert via rotation of the Co–C 1 bond. Subsequently, η 1 –η 3 isomerization 30 occurs to generate methoxide-coordinated η 3 -allyl-Co( iii ) species IM7a CSS - exo and IM7b CSS - endo (see the ESI Fig.…”

“…The ensuing C 3 –N reductive elimination via five-membered transition state ( R )- TS5 triplet leads to product-coordinated intermediate ( R )- IM12 triplet , which undergoes ligand exchange with ( rac )- 1a to furnish branched product ( R )- 3a . To generate branched product ( S )- 3a , the isomerization of IM10 triplet has to occur first through the rotation of the Co–C 1 bond to afford IM10′ triplet . This intermediate then undergoes C 3 –N reductive elimination via five-membered transition state ( S )- TS5 triplet to give product-coordinated intermediate ( S )- IM12 triplet , from which branched product ( S )- 3a can be obtained by the ligand exchange with ( rac )- 1a .…”

“…This intermediate then undergoes C 3 –N reductive elimination via five-membered transition state ( S )- TS5 triplet to give product-coordinated intermediate ( S )- IM12 triplet , from which branched product ( S )- 3a can be obtained by the ligand exchange with ( rac )- 1a . The formation of linear product E - 4a was found to commence with intermediate IM11 triplet , which can be formed by the homolytic cleavage of the Co–C 1 bond of IM10 triplet to produce an allyl radical followed by radical rebound (see the ESI Fig. S10† for details).…”

“…The development of highly efficient and atom-economical protocols for the selective construction of C–C and C–X bonds is of vital importance in organic synthesis. 1–3 Among the various methods developed, the transition metal-catalyzed allylic substitution reactions have garnered significant research attention and have been widely applied in the synthesis of natural products, materials and pharmaceuticals. 2 In this context, the second- and third-row transition metal complexes, in particular those of palladium, 4 iridium, 5 and rhodium, 6 are the most commonly used transition metal catalysts for this type of transformation.…”

Turning on Asymmetric Catalysis of Achiral Metal‐Organic Frameworks by Imparting Chiral Microenvironment

“…Therefore, it is of great importance and interest to develop simple and efficient strategies to synthesize optically pure compounds. [1] Over the past few decades, privileged homogeneous chiral catalysts have been developed, such as salen complexes, bis(oxazoline) ligands, and cinchona alkaloid derivatives. [2] However, the synthesis of these chiral ligands is usually too elaborate with complicated asymmetric reactions, [3] and the non-recyclability of homogeneous catalysts poses additional challenges for their practical use.…”