No abstract

Studies on the sp-sp intermolecular coupling reactions with the palladium water-soluble catalyst prepared in situ from palladium(I1) acetate and sulfonated triphenylphosphine P(C&bz-S03Na)3 (TPPTS) in a homogeneous acetonitrile-water system, without Cu(1) promotor, afford diynes with moderate yields (45-65%). Under the same conditions, the sp2-sp coupling of 2-iodophenols or 2-iodoanilines and terminal alkynes followed by intramolecular cyclization gives indolic and furanic products in good yields (60-99%). Under these aqueous conditions, an efficient and short synthesis of eutypine illustrated the synthetic potentiality of the coupling. Furthermore, through a series of kinetic and 31P NMR experiments, we have demonstrated that a mixture of Pd(0Ac)z and TPPTS affords spontaneously a palladium(0) complex, through formation of bivalent complex Pd(0Ac)z-(TPPTS)2. A detailed mechanism of the reaction has been investigated thoroughly and the pertinent rate constants measured. The resulting palladium(0) complex reacts with phenyl iodide via an oxidative addition. This complex is considerably less reactive than the corresponding complex generated from PPh3, probably due to steric effects.

Mononuclear iridium(III) complexes of general formula IrX(H)(O2CR)[(S)-binap] (2, R = CH3; 3, R = Ph; 4, R = C6H4CH3-p; a, X = Cl; b, X = Br; c, X = I) were prepared by one-pot reaction of [Ir(μ-X)(cod)]2 with 2 equiv of (S)-BINAP [=2,2‘-bis(diphenylphosphino)-1,1‘-binaphthyl] and an excess of the corresponding carboxylic acid in toluene. The structure of (S)-2−4 bearing an (S)-BINAP was confirmed to be OC-6−23-A (Λ-conformation) by X-ray analysis of (S)-4a−c. In this reaction, the iridium(I) complex {Ir(μ-Cl)[(S)-binap]}2 [(S)-5a] and pentacoordinated iridium(I) complexes IrX(cod)[(S)-binap] [(S)-7b, X = Br; (S)-7c, X = I] were generated prior to the oxidative addition of carboxylic acid. Cationic dinuclear iridium(III) complexes of general formula [{Ir(H)[(S)-binap]}2(μ-X)3]X [(S)-8:  a, X = Cl; b, X = Br; c, X = I] were prepared, and their cationic bifacial octahedral dinuclear structure was characterized by spectral data and combustion analysis. The anionic portion of these complexes could be replaced by NaPF6, leading to the corresponding PF6 salts [{Ir(H)[(S)-binap]}2(μ-X)3]PF6 [(S)-8:  d, X = Cl; e, X = Br; f, X = I]. Iodo-acetate complexes of p-TolBINAP (=2,2‘-bis(di-4-tolylphosphino)-1,1‘-binaphthyl) [(S)-9c] and SYNPHOS [=2,2‘,3,3‘-tetrahydro(5,5‘-bi-1,4-benzodioxin)-6,6‘-diyl]bis(diphenylphosphine)] [(S)-10c] were also prepared according to the method used for the BINAP complex (S)-2c and were characterized spectroscopically. Cationic dinuclear complexes of p-TolBINAP [(S)-11c] and SYNPHOS [(S)-12c] were also generated. Using these complexes, the effect of halide variation was studied by asymmetric hydrogenation of 2-phenylpyrrolidine (13) and 2-phenyl-4,5,6,7-tetrahydro-3H-azepine (15) along with 2-phenylquinoline (16), and the results indicated that iodide complexes were better catalyst precursors for catalytic activity than the corresponding chloride and bromide complexes, but were not superior in enantioselectivity.