Palladium-Catalyzed Tandem Cyclization/Suzuki Coupling of 1,6-Enynes

A Pd(0)-catalyzed 1,6-enyne cyclization−arylation cascade reaction was effected via π-allylpalladium intermediate formation and subsequent Suzuki coupling to give cyclic products with stereodefined exocyclic double bonds

Palladium-Catalyzed Tandem Cyclization/Suzuki Coupling Reaction of 1,2,7-Trienes

A Pd(0)-catalyzed 1,2,7-triene cyclization/arylation cascade reaction was realized via π-allylpalladium intermediate formation and a subsequent Suzuki coupling reaction to preferentially give a five-membered ring product with a stereodefined exocyclic double bond. Excellent cis/trans selectivity was achieved (only cis-3 was isolated) with heteroatom-tethered 1,2,7-triene substrates

<i>cis</i>-Chloropalladation of 1,6-Enynes

A PdCl2-catalyzed cis-chloropalladation−cyclization reaction of various 1,6-enyne substrates was developed. This Pd-catalyzed enyne cyclization reaction represents a new route for the synthesis of stereodefined α-halomethylene-γ-butyrolactones, lactams, tetrahydrofurans, and cyclopentanes. A mechanism involving a neighboring coordination group is proposed to explain the experiment results

Palladium-Catalyzed Cross-Coupling Reactions of Carboxylic Anhydrides with Organozinc Reagents

Negishi-type cross-coupling reaction was effected by employing organozincs and anhydrides or mixed anhydrides that formed in situ from sodium salts of the corresponding acids and ethyl chloroformate under the catalysis of palladium(0). A general method for preparing symmetrical/unsymmetrical ketones was developed

Synthesis of a Novel Chiral Binaphthyl Phospholane and Its Application in the Highly Enantioselective Hydrogenation of Enamides

A new chiral phosphine, (R,R)-1,2-bis{(R)-4,5-dihydro-3H-dinaphtho[2,1-c:1‘,2‘-e]phosphepino}benzene {abbreviated as (R,R)-binaphane] was prepared on the basis of a practical route from a readily accessible enantiomerically pure binaphthanol. This ligand possesses both binaphthyl chirality and phospholane functionality. Excellent enantioselectivities (95−99.6% ee) have been observed in hydrogenation of an isomeric mixture of (E)- and (Z)-β-substituted-α-arylenamides by using a Rh−binaphane catalyst. These enantioselectivities are the highest reported to date for this transformation

Synthesis of a Novel Chiral Binaphthyl Phospholane and Its Application in the Highly Enantioselective Hydrogenation of Enamides

A new chiral phosphine, (R,R)-1,2-bis{(R)-4,5-dihydro-3H-dinaphtho[2,1-c:1‘,2‘-e]phosphepino}benzene {abbreviated as (R,R)-binaphane] was prepared on the basis of a practical route from a readily accessible enantiomerically pure binaphthanol. This ligand possesses both binaphthyl chirality and phospholane functionality. Excellent enantioselectivities (95−99.6% ee) have been observed in hydrogenation of an isomeric mixture of (E)- and (Z)-β-substituted-α-arylenamides by using a Rh−binaphane catalyst. These enantioselectivities are the highest reported to date for this transformation

Synthesis of Bulky and Electron-Rich MOP-type Ligands and Their Applications in Palladium-Catalyzed C−N Bond Formation

A series of 2-dialkylphosphino-2‘-alkoxy-1,1‘-binaphthyl ligands (6a−c and 8a−c) have been prepared conveniently by a lithium-initiated ring-opening reaction of dinaphthofuran, followed by selective phosphorylation. These compounds displayed a remarkable air and moisture stability, both in solid form and in solution. Application of these phosphine ligands in palladium-catalyzed C−N bond forming reactions revealed the crucial roles of the steric bulk of the substituents on the phosphorus atom governing the catalytic activity. Specifically, 2-di-tert-butylphosphino-2‘-isopropoxy-1,1‘-binaphthyl (8b) proved to be the most effective for the aminations of aryl halides with primary amines, while the less bulky 2-dicyclohexyl-2‘-methoxy-1,1‘-binaphthyl (6a) was more effective for the aminations with secondary amines. The steric and electronic effects of the ligands were analyzed to account for these observations

Effect of Halide Ligands on the Reactivity of Carbon−Palladium Bonds: Implications for Designing Catalytic Reactions

The integral role of halide ions as a ligand in divalent palladium-catalyzed nucleophile−alkyne−α,β-unsaturated carbonyl coupling reaction as well as in the stoichiometric reaction of arylpalladium reagents with acrolein was studied. Excess of halide ions can effectively inhibit the β-hydride elimination of a (2-oxoalkyl)palladium intermediate, giving preferentially the protonolysis product in acidic media. This result may have further implications for the design and development of divalent palladium-catalyzed reactions

Highly Enantioselective Sequential Hydrogenation of Ethyl 2-Oxo-4-arylbut-3-enoate to Ethyl 2-Hydroxy-4-arylbutyrate

The hydrogenation of (E)-ethyl 2-oxo-4-arylbut-3-enoate with [NH2Me2]+[{RuCl [(S)-SunPhos]}2(μ-Cl3)] gave ethyl 2-hydroxy-4-arylbutyrate with 94−96% ee. Further investigation has proved that the hydrogenation proceeded via a sequential hydrogenation of CO and CC bonds, which is sensitive to the reaction temperature. Hydrolysis of ethyl 2-hydroxy-4-phenylbutyrate (ee 93%) provided the 2-hydroxy-4-phenylbutyric acid with 81% yield at 99% ee after a single recrystallization from 1, 2-dichloroethylene

Novel Rhodium-Catalyzed Cycloisomerization of 1,6-Enynes with an Intramolecular Halogen Shift

A new Rh-catalyzed 1,6-enyne cycloisomerization process with a π-allyl rhodium species as the key intermediate is investigated. A halogen shift happened in this novel process. The synthesis of stereodefined α-halomethylene γ-butyrolactones has been achieved using the readily accessible Rh catalysts