Enantioselective C–C bond formation in styrene dimerization with chiral ansa zirconocene-based catalyst

Enantioselective Nickel‐Catalyzed Cross‐Coupling Reactions of Trialkynylindium Reagents with Racemic Secondary Benzyl Bromides

“…With (S)-(iPr)-Pybox as the catalyst, 97 mg of 2 (70 %, 84 % ee) was formed; however, with (R)-(iPr)-Pybox as the catalyst, 93 mg of 3 (67 %, 82 % ee) was formed. (S)-1,3-Diphenylbutane: [16] A mixture of (1-methyl-3-phenyl-2-propynyl)-benzene 2 (prepared from reaction of 1 with tri(phenylethynyl)indium and (S)-(iPr)-Pybox as the catalyst, 39 mg, 0.368 mmol, 84 % ee) and Pd/ C (4 mg, 10 % Pd) in hexane (2 mL) was hydrogenated for 5 h (balloon pressure). After this time, the mixture was filtered through a short pad of Celite.…”

“…The use of other nickel catalysts, such as [NiA C H T U N G T R E N N U N G (cod) 2 ] (cod = 1,5-cyclooctadienyl) did not improve the yield, but using NiBr 2 ·diglyme at room temperature for 140 h, the reaction was complete and the coupling product 2 was obtained in 70 % yield with high enantioselectivity (84 % ee, Table 1, entry 8). [10] Other chiral ligands, such as (S)-(Ph)-Pybox, or different reaction conditions, led to lower yields, although maintaining the same level of enantioselectivity ( % 85 % ee; Table 1, entries 9 and 10).…”

Highly Selective Dimerization of Styrenes and Linear Co‐dimerization of Styrenes with Ethylene Catalyzed by a Ruthenium Complex

“…[3] Later, nickel- [4] and zirconium-based [5] catalyst systems were shown to be effective for this dimerization reaction, and these generally gave head-to-tail dimers, namely (E)-1,3-diaryl-1-butenes. There has been only one previous example of head-to-head dimerization to give (E)-1,4-diaryl-1-butene: Kretschmer et al [6] reported that the use of a bis(indenyl)yttrium hydride as the catalyst gave such a dimerization.…”

Differences between insertions of ethylene into metallocene and non‐metallocene ethylene polymerization catalysts

“…The Cossee mechanism has been widely accepted to elucidate olefin coordination polymerization mediated by both heterogeneous catalysts and homogeneous metallocene and non‐metallocene catalysts and often applied in molecular modeling studies of olefin polymerizations . Scheme illustrates the Cossee mechanism, an insertion step in polymerization process proceeds by first forming a stable π complex between olefin and the activated cationic catalyst which bears an alkyl group or growing polymer chain, followed by the insertion of ethylene C = C double bond into M(metal)―C bond via a TS (transition state), leading to the cationic insertion PR (product).…”