Aldimine‐Directed Branched‐Selective Hydroarylation of Styrenes

Cobalt-Catalyzed C-C Bond-Forming Reactions via Chelation-Assisted C-H Activation

“…A catalyst generated from CoBr 2 , PPh 3 or P(p Tol) 3 , and Me 3 SiCH 2 MgCl promotes the addition of an aryl aldimine to styrene at 40 , affording the corresponding 1,1 diarylethane product with high regioselectivity (Scheme 10). 25 The reaction of an ortho unsubstituted aldimine afforded an ortho dialkylated product as the major product even when the amount of styrene was limited. This observation may be ascribed to strong coordination of the aldimine moiety to the catalyst.…”

Development of Cobalt-Catalyzed C–H Bond Functionalization Reactions

“…A catalyst generated from CoBr 2 , PPh 3 or P(p-Tol) 3 , and Me 3 SiCH 2 MgCl promotes the styrene hydroarylation using aromatic aldimines at 40°C, affording the corresponding 1,1-diarylethane products with high regioselectivity (Scheme 10a). 33 Note that the reaction of ortho-unsubstituted aldimines led to the formation of dialkylation products even when a limited amount of styrene was used. This suggests that the coordination of the aldimine to the catalyst is relatively strong, and that the first alkylation is immediately followed by the second CH activation.…”

CH Alkenylations with Alkenyl Acetates, Phosphates, Carbonates, and Carbamates by Cobalt Catalysis at 23 °C

“…To our delight, in situ generated N-heterocyclic carbenes (NHCs) derived from inexpensive imidazolium salts (Figure 1) facilitated the desired transformation even at an ambient reaction temperature of 23 8C (entries 5-12), with optimal results being obtained with the preligand IPrHCl (4 c; entry 7). Among a variety of representative bases and solvents, CyMgCl and DMPU, respectively, were found to be ideal (entries [11][12][13][14][15][16][17][18][19]. Importantly, the reaction did not proceed in the absence of the NHC ligand or the cobalt complex (entries 1 and 20).…”

“…[6,7] As of yet, cobalt-catalyzed C À H olefinations have been solely accomplished through hydroarylations [8] of alkynes. [7,9] Despite significant advances by Yoshikai and coworkers, [10,11] this approach continues to face considerable limitations, including the difficulty of controlling regioselectivity as well as the inherent limitation to the synthesis of acyclic alkenes.…”