6704-79-6Relevant academic research and scientific papers
(CDC)-Rhodium-catalyzed hydroallylation of vinylarenes and 1,3-dienes with allyltrifluoroborates
Marcum, Justin S.,Cervarich, Tia N.,Manan, Rajith S.,Roberts, Courtney C.,Meek, Simon J.
, p. 5881 - 5889 (2019/08/15)
Catalytic site-selective hydroallylation of vinyl arenes and 1,3-dienes is reported. Transformations are promoted by a readily accessible bidentate carbodicarbene-rhodium complex and involve commercially available allyltrifluoroborates and an alcohol. The reaction is applicable to vinyl arenes and aryl-or alkyl-substituted 1,3-dienes (30 examples). Allyl addition products are generated in 40-78% yield and in up to >98:2 site selectivity. Reaction outcomes are consistent with the intermediacy of a Rh(III)-hydride generated by protonation of Rh(I) by an acid. A number of key mechanistic details of the reaction are presented: (1) Deuterium scrambling into the product and starting alkene indicates reversible Rh(III)-H migratory insertion. (2) A large primary kinetic isotope effect is observed. (3) With substituted allyltrifluoroborates (e.g., crotyl-BF3K) mixtures of site isomers are generated as a result of transmetalation followed by Rh-(allyl) complex equilibration, consequently disproving outer-sphere addition of the allyl nucleophile to Rh(III)-(η3-allyl). (4) Stereochemical analysis of a cyclohexadiene allyl addition product supports a syn Rh(III)-hydride addition. (5) A Hammett plot shows a negative slope. Finally, utility is highlighted by a iodocyclization and cross metathesis.
Heterodimerization of Olefins. 1. Hydrovinylation Reactions of Olefins That Are Amenable to Asymmetric Catalysis
RajanBabu,Nomura, Nobuyoshi,Jin, Jian,Nandi, Malay,Park, Haengsoon,Sun, Xiufeng
, p. 8431 - 8446 (2007/10/03)
Through a systematic examination of ligand and counterion effects, new protocols for a nearly quantitative and highly selective codimerization of ethylene and various functionalized vinylarenes have been discovered. In a typical reaction, 4-bromostyrene and ethylene undergo codimerization in the presence of 0.0035 equiv each of [(allyl)NiBr]2, triphenylphosphine, and AgOTf in CH2Cl2 at -56 °C to give 3-(4-bromophenyl) -1-butene in >98% yield and selectivity. Corresponding reactions with [(allyl)PdX]2 are much less efficient and less selective and may require further optimization before a viable system can be identified. Another useful protocol that gives comparable yield and selectivity involves the use of a single-component catalyst prepared from allyl 2-diphenylphosphinobenzoate, Ni(COD)2, and (C6F5)3B. Recognition of a synergistic relationship between a chiral hemilabile ligand (for example, (R)-2-methoxy-2′-diphenylphosphino-1,1′-binaphthyl, MOP) and a highly dissociated counteranion (BARF or SbF6) in an enantioselective version of the Ni-catalyzed reaction raises the prospects of developing a practical route for the synthesis of 3-arylbutenes. Several pharmaceutically relevant compounds, including widely used 2-arylpropionic acids, can be synthesized from these key intermediates. This reaction appears to be quite general. Synthesis of several new 2-diphenylphosphino-1,1-binaphthyl derivatives, prepared to probe the effect of hemilabile coordination on the efficiency and selectivity of the reaction, are also described.
PALLADIUM-CATALYZED ASYMMETRIC COUPLING REACTIONS BETWEEN ALLYLIC ACETATES AND ORGANOZINC REAGENTS. MECHANISTIC IMPLICATIONS
Fiaud, Jean-Claude,Aribi-Zouioueche, Louisa
, p. 383 - 388 (2007/10/02)
Asymmetric induction and deuterium distribution studies have provided information about the mechanism of the palladium-catalyzed coupling reaction between allylic acetates and phenylzinc chloride, namely the presence of a symmetric η3-allylic ligand in the inetrmediate, probably along with a monodentate phosphine ligand.
