Rhodium complex catalysed hydrosilylation of carbonyl compounds

Ojima, Iwao; Nihonyanagi, Mitsuru; Nagai, Yoichiro

doi:10.1039/c3972000938a

Cited by 153 publications

(50 citation statements)

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“…Complex 1 b was treated 3 ) 2 groups in the newly formed species) was observed. These signals could either imply the formation of two new compounds or the formation of one species in which both IPr ligands on the copper center are inequivalent.…”

Section: Resultsmentioning

confidence: 94%

“…Complexes with the bulkiest ligands (IAd and ItBu; 6 a, 6 b, and 7 b) have the longest Cu À C bond lengths and a torsion angle between the NHC ligands of close to 908 ( (Table 2), which has two bulky SIPr ligands, has a long Cu À C bond length, but the ligands are only slightly twisted. In this particular case, the presence of two sp 3 carbon atoms in the heterocyclic ring allowed the formation of torsion angles of 15.7 and 8.7 8 in the saturated backbones of the SIPr ligands. Interestingly, SIMes complexes 4 a and 4 b do not show such a feature and the imidazoline rings are planar.…”

Section: Resultsmentioning

confidence: 97%

“…In contrast, since the first report of a metal-catalyzed hydrosilylation of ketones in the presence of the Wilkinsons catalyst, [3] smooth reaction conditions can be employed, and in consequence, overreduced products are rarely detected. A sequence of hydrosilylation/hydrolysis reactions leads to the formation of alcohols and amines.…”

Section: Introductionmentioning

confidence: 81%

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Synthesis and Characterization of [Cu(NHC)₂]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

Díez‐González

Stevens

Scott

et al. 2007

Chemistry A European J

153

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The preparation of two series of [Cu(NHC)2]X complexes (NHC=N-heterocyclic carbene, X=PF6 or BF4) in high yields from readily available materials is reported. These complexes have been spectroscopically and structurally characterized. The activity of these cationic bis-NHC complexes in the hydrosilylation of ketones was examined, and both the ligand and the counterion showed a significant influence on the catalytic performance. Moreover, when compared with related [Cu(NHC)]-based systems, these cationic complexes proved to be more efficient under similar reaction conditions. The activation step of [Cu(NHC)2]X precatalysts towards hydrosilylation was investigated by means of 1H NMR spectroscopy. Notably, it was shown that one of the N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) ligands in [Cu(IPr)2]BF4 is displaced by tBuO(-) in the presence of NaOtBu, producing the neutral [Cu(IPr)(OtBu)]. This copper alkoxide is known to be a direct precursor of an NHC-copper hydride, the actual active species in this transformation. Furthermore, reagent loading and counterion effects have been rationalized in light of the species formed during the reaction.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 97%

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Synthesis and Characterization of [Cu(NHC)₂]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

Díez‐González

Stevens

Scott

et al. 2007

Chemistry A European J

153

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“…The positioning of the substituents on the aromatic ring of acetophenone had significant effect on the outcome of reactions. The ortho-substituted acetophenones (2d-2f ) were converted to the desired alcohols with moderate enantioselectivities (70-77% ee, Table 2, entries 3-5), whereas meta-and para-substituted acetophenones (2g-2o) gave consistently high enantioselectivities (87-97% ee, Table 2, entries [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Resultsmentioning

confidence: 99%

A remarkably effective copper(II)-dipyridylphosphine catalyst system for the asymmetric hydrosilylation of ketones in air

Chan

2005

Proc. Natl. Acad. Sci. U.S.A.

105

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The combination of catalytic amounts of optically active dipyridylphosphine and CuF 2 along with hydride donor PhSiH3 generated in situ a remarkably reactive catalyst system (substrate-toligand molar ratio up to 100,000) for the highly enantioselective hydrosilylation of a broad spectrum of aryl alkyl ketones (up to 97% enantiomeric excess) in normal atmosphere and at mild conditions (ambient temperature to ؊20°C, compatible with traces of moisture) in the absence of base additives. Furthermore, a highly effective catalytic asymmetric hydrosilylation of unsymmetrical diarylketones using this catalyst system was also realized (up to 98% enantiomeric excess). The introduction of the dipyridylphosphine ligands in the air-accelerated and inexpensive metal-mediated asymmetric hydrosilylation of ketones makes the present system highly attractive and thus provides an excellent opportunity for practical applications.asymmetric catalysis C onsiderable efforts have been devoted to the development of efficient methods for the preparation of enantiomerically pure secondary alcohols because of the significance of these intermediates for the manufacture of pharmaceuticals and advanced materials. The catalytic asymmetric reduction of prochiral ketones as a direct route to enantiomeric alcohols is among the most attractive, and various strategies have been developed accordingly (1-5). Although intensive studies have been focused on the asymmetric hydrogenation that shows excellent enantioselectivities for a wide range of simple ketones (refs. 6 and 7 and references therein and refs. 8 -18), asymmetric hydrosilylation as a desirable alternative has also attracted much attention, owing to the mild reaction conditions used and technical simplicity (1d). Since the early reports three decades ago (19 -23), the asymmetric hydrosilylations of prochiral simple ketones mediated by catalysts of rhodium(I) (4, 24 -28) and ruthenium(II) (29, 30) as well as some less expensive metals such as titanium (31-34), zinc (35), tin (36), and copper(I) (37) have been extensively explored. However, most of these reactions were routinely conducted at a low substrate-to-ligand (S͞L) ratio (50 to 500). The high cost of catalyst and the low substrate-to-catalyst ratio rendered the previous hydrosilylation work unattractive commercially. More recently, a significant breakthrough in this area was achieved by , who developed a very effective catalyst system formed in situ from CuCl and nonracemic bidentate phosphines [e.g., (6,6Ј-dimethoxybiphenyl-2,2Ј-diyl)bis[di(3,5-dimethylphenyl)phosphine] (41, 42) or (4,4Ј-bi-1,3-benzodioxol)-5,5Ј-diylbis(di(3,5-di-tert-4-methoxyphenyl)phosphane) (43)] along with t-BuONa. This system allowed for highly active and enantioselective hydrosilylations of both aryl alkyl and heteroaromatic ketones in the presence of an inexpensive stoichiometric reductant polymethylhydrosiloxane (44) even at a S͞L molar ratio up to 100,000, which approached the levels achieved in related ruthenium-based asymmetric hydrogenations (ref. 6 and ...

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“…It was not until the '70s, that the first Rh(I) based catalyst, used for reductive hydrosilylation of ketones and imines, yielding, respectively, alcohols and amines were developed [1][2][3]. The softer reaction conditions of hydrosilylation, turned out to be a major advantage over other reduction reactions, such as hydrogenation.…”

Section: Introductionmentioning

confidence: 98%

Mechanism of ketone hydrosilylation by Cu(I) catalysts: A theoretical study

Gathy¹,

Peeters²,

Leyssens³

2009

Journal of Organometallic Chemistry

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Rhodium complex catalysed hydrosilylation of carbonyl compounds

Cited by 153 publications

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Synthesis and Characterization of [Cu(NHC)₂]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

Synthesis and Characterization of [Cu(NHC)₂]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

A remarkably effective copper(II)-dipyridylphosphine catalyst system for the asymmetric hydrosilylation of ketones in air

Mechanism of ketone hydrosilylation by Cu(I) catalysts: A theoretical study

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Rhodium complex catalysed hydrosilylation of carbonyl compounds

Cited by 153 publications

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Synthesis and Characterization of [Cu(NHC)2]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

Synthesis and Characterization of [Cu(NHC)2]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

A remarkably effective copper(II)-dipyridylphosphine catalyst system for the asymmetric hydrosilylation of ketones in air

Mechanism of ketone hydrosilylation by Cu(I) catalysts: A theoretical study

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Synthesis and Characterization of [Cu(NHC)₂]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions

Synthesis and Characterization of [Cu(NHC)₂]X Complexes: Catalytic and Mechanistic Studies of Hydrosilylation Reactions