Enantioselective catalysis XVI: regio- and enantioselectivity in nickel-catalysed cross-coupling reactions of allylic substrates with Grignard reagents

Enantioselective and Enantiospecific Transition-Metal-Catalyzed Cross-Coupling Reactions of Organometallic Reagents To Construct C–C Bonds

“…Similar regioselectivity was observed when diphosphine L70 was employed. 226 Symmetrical acyclic electrophiles were instead required to avoid the formation of regioisomers ( Scheme 26 b). Whereas cyclic substrates reacted with poor enantioselectivity under Consiglio’s conditions, Uemura and co-workers determined that Ni/ L29 delivers cyclic product 272 in high ee ( Scheme 26 c).…”

“…When acyclic pivalate 266 was utilized, 267 was obtained in a promising 89% ee, but as a mixture with the linear coupling product 268 . Similar regioselectivity was observed when diphosphine L70 was employed . Symmetrical acyclic electrophiles were instead required to avoid the formation of regioisomers (Scheme b).…”

Regioselective Palladium-Catalyzed Alkylation of Allylic Halides with Benzylic Grignard Reagents. Two-Step Synthesis of Abietane Terpenes and Tetracyclic Polyprenoid Compounds

“…During this transformation, the leaving group (Y, Scheme ) can be displaced either in an α (S N 2) or γ (S N 2‘) fashion by the organometallic reagent (M-catalyst). The development of chiral catalysts for the asymmetric formation of the γ-product (S N 2‘ process) has emerged as an important branch of research endeavors . On the other hand, the α-allylation (S N 2 process) has not received the same degree of attention presumably due to the lack of generality, difficulties in preparing the catalyst or generating the Grignard reagent, and scarce applications of the resulting products.…”