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.

Asymmetric hydrogenation by using chiral transitionmetal complexes represents one of the cleanest and most environmentally benign processes available for producing optically pure organic compounds.[1] Currently, a wide variety of chiral compounds with outstanding levels of enantioselectivity has been synthesized by reduction of C=C, [1] C= O, [2,3] C=N, [4][5][6] and, more recently, heteroaromatics compounds. [7][8][9][10][11][12][13][14][15][16][17][18] Among heteroaromatics, 2-substituted quinolines have been targeted [9][10][11][12][13][14][15][16][17][18] because optically active 2-substituted-1,2,3,4-tetrahydroquinoline derivatives are key components of many bioactive natural products and drugs. [19] In contrast with the successful asymmetric hydrogenation of 2-alkyl-substituted quinolines catalyzed by chiral iridium complexes with an iodide source or iodine, [9][10][11][12][13] which dramatically enhances both catalytic activity and enantioselectivity, [5, 9a] only limited success has been achieved in the catalytic hydrogenation of 2-aryl-substituted quinolines. So far, the only known examples used 2-phenylquinoline as a unique model substrate. The first example of catalytic hydrogenation of 2-phenylquinoline (72 % ee (enantiomeric excess)), described by Zhou and co-workers, [9a] is based on anMeO-biphep/I 2 (cod = 1,5-cyclooctadiene; MeO-biphep = 6,6'-dimethoxy-2,2'-bis(diphenylphosphino)-1,1'-biphenyl) catalytic system that was recently improved to 80 % ee with a moderate yield of 41 % by using benzyl chloroformate as an activating agent, although this required an additional deprotection step on the resulting carbamate. [18] In recent years, only a few examples of the catalytic hydrogenation of 2-phenylquinoline have been reported with ee values up to 88 %. [14] We describe herein a highly enantioselective hydrogenation of the HX salts (X = Cl, Br, and I) of various 2-aryl-substituted quinolines by using cationic dinuclear iridium complexes [6,17] with [(4,4'-bi-2,2-difluoro-1,3-benzodioxole)-5,5'-diyl]bis(diphenylphosphine) (difluorphos), [20] which demonstrates an unexpected halide effect in which iridium complexes with chloro and bromo ligands serve as better catalysts than an iodo-iridium complex. The present catalyst was also effective for the hydrogenation of 2-alkyl-substituted quinolinium salts, which shows the high versatility of this new catalyst system. Furthermore, this system was applied to a formal asymmetric synthesis of selective estrogen receptor modulator (SERM) 6-hydroxy-2-(4-hydroxyphenyl)-1-{4-[2-(pyrrolidin-1-yl)ethoxy]-benzyl}-1,2,3,4-tetrahydroquinoline (1) [21] by asymmetric hydrogenation of the HCl salt of 6-methoxy-2-(4-methoxyphenyl)quinoline (2·Cl) as a key step.We recently developed cationic dinuclear triply halogen- [3][4][5][6][7][8] X= Cl, Br, and I) (Figure 1), which were conveniently prepared by adding excess aqueous HX to a mixture of [{IrClA C H T U N G T R E N N U N G (coe) 2 } 2 ] (coe = cyclooctene) and the required chiral diphosphine ligand in toluene at room...

A highly enantioselective catalytic hydrogenation of cyclic enones was achieved by using the combination of a cationic Rh(I) complex, (S)-5,5'-bis{di(3,5-di-tert-butyl-4-methoxyphenylphosphino)}-4,4'-bi-1,3-benzodioxole (DTBM-SEGPHOS), and (CH2CH2PPh3Br)2. The presence of an s-cis C=C bond isopropylidene moiety on the cyclic enone influenced the enantioselectivity of the hydrogenation. Thus, the hydrogenation of 3-alkyl-6-isopropylidene-2-cyclohexen-1-one, which contains both s-cis and s-trans enones, proceeded in excellent enantioselectivity (up to 98 % ee). To obtain high enantio- and s-trans selectivities, the addition of a halogen source to the cationic Rh complex was the essential step. With the key step of the s-trans selective asymmetric hydrogenation of piperitenone, we demonstrated a new synthetic method for optically pure (-)-menthol via three atom-economical hydrogenations. Moreover, we found that the complete s-trans and s-cis C=C bond selective reactions were also realized by the proper choice of both the chiral ligands and halides.

Halide Ligands. -An unexpected superiority of the axially chiral chloro-and bromo-iridium complexes (I) over the corresponding iodo-complex as catalysts for the title reaction of 2-aryl-and 2-alkylquinolinium halides is observed. The method is applied as key step for the synthesis of bioactive compound (X).

Novel Ir-SYNPHOS and Ir-DIFLUORPHOS catalysts were synthesized and used for the synthesis of tetrahydroquinolines via asymmetric hydrogenation of the corresponding quinoline derivatives.

DEPORT, C.; BUCHOTTE, M.; ABECASSIS, K.; TADAOKA, H.; AYAD, T.; OHSHIMA, T.; GENET, J.-P.; MASHIMA, K.; RATOVELOMANANA-VIDAL*, V.; Synlett

Ni-Catalyzed Arylation of Bromomagnesium Diarylamides with Aryl N,N-Dimethylsulfamates. -The procedure allows the synthesis of triarylamines as well as symmetrical or unsymmetrical diamines for use in light-emitting materials. -(TADAOKA, H.; YAMAKAWA*, T.; Tetrahedron Lett. 53 (2012) 41, 5531-5534, http://dx.

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