Ruthenium unsaturated ketone

The most important ruthenium-catalyzed domino process is based on a metathesis reaction. Nonetheless, a few other ruthenium-catalyzed processes have been employed for the synthesis of substituted 3,y-unsaturated ketones, as well as unsaturated y-lactams and allylic amines. 

The proposed mechanism involves coordination of allene and ce,/j-unsaturated ketone to the cationic cydopentadienylruthenium species 137. Subsequent formation of the ruthenacyde 139, followed by /3-hydride elimination, generates the ruthenium hydride species 140. Finally, reductive elimination closes the cycle and regenerates the ruthenium intermediate 137 (Scheme 14.33) [68, 71]. 

R)-BINAP/l,2-diphenylethylenediamine ruthenium(II) complexes covalently attached to polystyrene (Scheme 4.32) promote the asymmetric hydrogenation of aromatic ketones and of a, yS-unsaturated ketones [125]. The catalysts (52) and (53) were reused at high substrate/catalyst molar ratio (S/C) of 2470 in 14 experiments. Remarkably, the enantiopurity of the products remained high after each run, constantly being in the range of 97 to 98% ee. 

Trust s group has shown that another selective reaction involving C—O bond formation followed by rearrangement and C—C bond formation occurred when Cp-containing ruthenium complexes were used as catalytic precursors. With RuCl(Cp)(PPh3)2 in the presence of NH4PF6, an additive known to facilitate chloride abstraction from the metal center, the addition of allylic alcohols to terminal alkynes afforded unsaturated ketones [46, 47]. It has been shown that the key steps are the... 

A ruthenium-catalysed, three-component addition of alkync to x,/(-unsaturated ketones to produce 1,5-diketones has been developed (Scheme 32).113... 

PhanePhos-ruthenium-diamine complexes catalyze the asymmetric hydrogenation of a wide range of aromatic, heteroaromatic, and cx,P-unsaturated ketones with high activity and excellent enantioselectivity (Burk, 2000). 

Lindner, E. Ghanem, A. Warad, I. Eichle, K. Mayer, E. Schurig, V. Asymmetric hydrogenation of an /J-unsaturated ketone by diamine(ether-phosphine)ruthenium(II) complexes and lipase-catalyzed kinetic resolution a consecutive approach. Tetrahedron Asymmetry 2003, 14, 1045-1053. 

A one-pot quinoline synthesis starting with 2-aminobenzyl alcohol and a,/3-unsaturated ketones using ruthenium-grafted hydrotalcites as a heterogeneous catalyst has been reported (Scheme 64) <2004TL6029>. Molecular oxygen was used for the oxidation of ruthenium and the styryl quinoline 42 was produced in good yield. The use of other donors, for example, octanal and phenylacetonitrile, yielded 3-amylquinoline and 2-amino-3-phenylquinoline, respectively. 

Dimcthyl 2-(but-2-ynyl)-2-(5-oxopent-3-enyl)malonates 96 undergo ruthenium-catalyzed intramolecular cycli-zations to yield cyclohexyl fused 4//-pyrans 97, most likely via formation of and reductive elimination from the ruthenacycle intermediate 98 (Scheme 32). Likewise, internal alkynes tethered to an a, 3-unsaturated ketone via a three-component chain undergo mthenium-catalyzed cyclizations furnishing 4//-pyrans that are fused to five-membered rings 99 (Equation 50) <2000JA5877>. 

Preparation of the JST class (see Section 12.3.4) of the ruthenium-diphosphine-diamine complex, [(PhanePhos)Ru(diamine)Cl2], produced highly active and enantioselective catalysts in the reduction of aryl methyl ketones (128, R = Me), as well as a,P-unsaturated ketones.162-163 Higher... 

Activation of vinyl C-H bonds with RuH2(CO)(PPh3)3 catalyst has allowed the formal insertion of a,/l-unsaturated ketones or esters into the C-H bond of vinylsilanes and led to a regioselective C-C coupling at the -position [9] (Eq. 6). Activation of the sp2 C-H bond occurred with the aid of chelation of a coordinating functional group and provided vinylruthenium hydride 14. Insertion of olefin afforded the tetrasubstituted alkene 13. The ruthenium activation of a variety of inert C-H bonds has now been performed by Murai [10]. 

A similar mechanism,based on a ruthenacyclopentene, can be proposed for the coupling of alkynes and allylic alcohols to lead to y,<5-unsaturated aldehydes and ketones. When (C5H5)RuC1(COD) was used as a catalyst, the ruthenium-catalyzed coupling between alkynes and substituted allylic alcohols afforded y,<5-unsaturated ketones. The linear isomer was the major product [39] (Eq. 28). Similarly, the linear derivative was also obtained when an allylsi-lylether or an allylic amide was used in place of the allyl alcohol, leading to 1,4-dienes [40]. 

The selective intramolecular nucleophilic addition of a hydroxy group at Cyof a ruthenium allenylidene generated by activation of propargylic alcohol by RuCl(Cp)(PPh3)2/NH4PF6 provides a ruthenium vinylidene species, which reacts with allylic alcohols as previously described in the section Formation of Unsaturated Ketones (Eq. 11, Scheme 18) [79]. This unprecedented tandem reaction makes possible the construction of tetrahydrofuran derivatives in good yields and has been used as a key step in the synthesis of (-)calyculin A [80]. 

The ruthenium complex (C5H5)RuCl(PPh3)2 with NH4PF6 catalyzes the addition of allylic alcohols to terminal alkynes, yielding /3,y-unsaturated ketones (Eq. 5.23) [38]. This process involves the nucleophilic attack of allylic alcohols to a (vinylide-ne)ruthenium intermediate, leading to the formation of an (acyl)(jr-allyl)ruthenium intermediate. 

A similar ruthenium complex (C5H5)RuCl(cod) catalyzes a totally different reaction pathway for alkynes and allylic alcohols to produce y,d-unsaturated ketones, which involves a ruthenacyclopentene intermediate, rather than a jt-allylmthenium intermediate [39]. 

In this reaction, carbon monoxide is not needed. The key intermediate is an (acyl)(jt-allyl)ruthenium complex that undergoes reductive elimination to give the corresponding /3,y-unsaturated ketones. 

With the catalysts derived from (S,S)-l,2-bis(diphenylphosphinomethyl)cyclobutane and [RhH(CO)(PPh3)3] or rhodium carbonyls, the a,3-unsaturated aldehydes, neral and geranial, are hydrogenated to (E)- and (S)-citronellal in 79% and 60% ee, respectively. Cyclic a,3-unsaturated ketones such as isophorone and 2-methyl-2-cyclohexenone have been hydrogenated using ruthenium hydrides coordinated with chiral diphosphines in up to 62% ee to give chiral ketones, though conversions are not satisfactory. ... 

Breitner et al. of Engelhard Industries report comparisons of the activities of commercial preparations of Rh-C, Ru-C, Pt-C, and Pd-C (all on Norit). Rhodium-C and ruthenium-C appear to be the catalysts of choice for the hydrogenation of ketones in a neutral or basic medium. These catalysts can be used for the reduction of a,/3-unsaturated ketones, via the saturated ketones, to the saturated alcohols. 

Ruthenium-catalyzed allylation of primary alcohols by allylic acetates to give a, 3-unsaturated ketones has been reported (Eq. 11) [22]. 

Ruthenium-catalyzed hydroacylation of 1,3-dienes with aromatic and heteroaromatic aldehydes occurs in relatively good yields to afford the corresponding fi, /-unsaturated ketones . Isoprene and benzaldehyde were treated with 4 mol% Ru(COD)(COT) (COD = 1,5-cyclooctadiene, COT = 1,3,5-cyclooctatriene) and 4 mol% PPhs under argon for 40 hours to give 54% 80 (equation 41). The key intermediate is an acyl- ) -(allyl)ruthenium complex which undergoes reductive elimination to give the corresponding... 

Trost, B.M., Martinez, J.A., Kulawiec, R.J. and Indolese, A.F. (1993) Ruthenium-catalyzed addition of allyl alcohols and acetylenes. A simple synthesis of y,8-unsaturated ketones. Journal of the American Chemical Society, 115, 10402-10403. 

Surprisingly, there are only a few catalysts known capable of hydrogenating ketones in fully or largely aqueous systems. For example, most of the water-soluble rhodium, ruthenium and indium phosphine complexes preferentially hydrogenate the C=C bonds in unsaturated ketones, as does the solvated ion pair formed from aqueous rhodium trichloride and Aliquat-336 [206]. 

Deacylation." Removal of an entire acyl side chain from an aromatic ketone occurs when the acyl group is ortho to a potential ligand for ruthenium. Accordingly, this process exhibits excellent regioselectivity in the cases of certain diacylarenes. The importance of the coordination is shown by the fate of a p-(2-pyridyl)-a,p-unsaturated ketone. 

---