Sergio E. García-Garrido

Ruthenium-catalyzed redox isomerization/transfer hydrogenation in organic and aqueous media: A one-pot tandem process for the reduction of allylic alcohols

The hexamethylbenzene-ruthenium(II) dimer [{RuCl(μ-Cl)(η6-C6Me6)}2] 1 and the mononuclear bis(allyl)-ruthenium(IV) complex [RuCl2(η3:η2:η3-C12H18)] 2, associated with base and a hydrogen donor, were found to be active catalysts for the selective reduction of the CC bond of allylic alcohols both in organic and aqueous media. The process, which proceeds in a one-pot manner, involves a sequence of two independent reactions: (i) the initial redox-isomerization of the allylic alcohol, and (ii) subsequent transfer hydrogenation of the resulting carbonyl compound. The highly efficient transformation reported herein represents, not only an illustrative example of auto-tandem catalysis, but also an appealing alternative to the classical transition-metal catalyzed CC hydrogenations of allylic alcohols. The process has been successfully applied to aromatic as well as aliphatic substrates affording the corresponding saturated alcohols in 45–100% yields after 1.5–24 h. The best performances were reached using (i) 1–5 mol% of 1 or 2, 2–10 mol% of Cs2CO3, and propan-2-ol or (ii) 1–5 mol% of 1 or 2, 10–15 equivalents of NaO2CH, and water. The catalytic efficiency is strongly related to the structure of the allylic alcohol employed. Thus, in propan-2-ol, the reaction rate essentially depends on the steric requirement around the CC bond, therefore decreasing with the increasing number of substituents. On other hand, in water the transformation is favoured for primary allylic alcohols vs. secondary ones.

Water-soluble ruthenium(II) catalysts [RuCl2(η6-arene)-{P(CH2OH)3}] for isomerization of allylic alcohols and alkyne hydration

The novel water-soluble ruthenium(II) complexes [RuCl(2)(eta(6)-arene)[P(CH(2)OH)(3)]]2a-c and [RuCl(eta(6)-arene)[P(CH(2)OH)(3)](2)][Cl]3a-c have been prepared in high yields by reaction of dimers [[Ru(eta(6)-arene)(micro-Cl)Cl](2)](arene = C(6)H(6)1a, p-cymene 1b, C(6)Me(6)1c) with two or four equivalents of P(CH(2)OH)(3), respectively. Complexes 2/3a-c are active catalysts in the redox isomerization of several allylic alcohols into the corresponding saturated carbonyl compounds under water/n-heptane biphasic conditions. Among them, the neutral derivatives [RuCl(2)(eta(6)-C(6)H(6))[P(CH(2)OH)(3)]]2a and [RuCl(2)(eta(6)-p-cymene)[P(CH(2)OH)(3)]]2b show the highest activities (TOF values up to 600 h(-1); TON values up to 782). Complexes 2/3a-c also catalyze the hydration of terminal alkynes.

Dichloro(dodeca-2,6,10-triene-1,12-diyl)ruthenium(IV): a highly efficient catalyst for the isomerization of allylic alcohols into carbonyl compounds in organic and aqueous media

The catalytic activity of the bis(allyl)-ruthenium(iv) complex [Ru([small eta](3):[small eta](2):[small eta](3)-C(12)H(18))Cl(2)] in the transposition of allylic alcohols into carbonyl compounds, both in THF and H(2)O as solvent, is reported.

[Ru(η3-2-C3H4Me)(CO)(dppf)][SbF6]: a mononuclear 16e− ruthenium(II) catalyst for propargylic substitution and isomerization of HCCCPh2(OH)

The 16e(-) derivative [Ru(eta3-2-C3H4Me)(CO)(dppf)][SbF6] catalyzes: (i) the propargylic substitution reaction of 1,1-diphenyl-2-propyn-1-ol with alcohols to produce propargylic ethers, and (ii) the formal isomerization of 1,1-diphenyl-2-propyn-1-ol into 3,3-diphenyl-2-propenal.

Bis(allyl)-Ruthenium(IV) Complexes: Promising Precursors for Catalytic Organic Synthesis

The present review reports on the chemistry of the bis(allyl)-ruthenium(IV) complexes ({Ru(η 3 :η 3 -C10H16)(μ- Cl)Cl}2) (C 10H16 = 2,7-dimethylo cta-2,6-diene-1,8-diyl) and (Ru(η 3 :η 2 :η 3 -C12H18)Cl2) (C 12H18 = dodeca-2,6,10 -triene- 1,12-diyl). Stoichiometric reactions allowing the preparation of a variety of organoruthenium(IV) and (II) derivatives, as well as the involvement of these species in a series of catalytic organic transformations are presented.

Neutral and cationic (η6-arene)-ruthenium(II) complexes containing the iminophosphorane-phosphine ligand Ph2PCH2P(=N-p-C5F4N)Ph2: influence of the arene ring in catalytic transfer hydrogenation of cyclohexanone

Abstract Ruthenium(II) dimers [{Ru(η 6 -arene)(μ-Cl)Cl} 2 ] ( 1a – f ) readily react with the iminophosphorane–phosphine ligand Ph 2 PCH 2 P(N- p -C 5 F 4 N)Ph 2 ( 2 ), in dichloromethane at room temperature, to afford the neutral derivatives [Ru(η 6 -arene)Cl 2 { k 1 - P -Ph 2 PCH 2 P(N- p -C 5 F 4 N)Ph 2 }] (arene=C 6 H 6 ( 3a ), 1- i Pr-4-C 6 H 4 Me ( 3b ), 1,3,5-C 6 H 3 Me 3 ( 3c ), 1,2,3,4-C 6 H 2 Me 4 ( 3d ), 1,2,4,5-C 6 H 2 Me 4 ( 3e ), C 6 Me 6 ( 3f )). Treatment of 3a – f with AgSbF 6 in dichloromethane yields the cationic species [Ru(η 6 -arene)Cl{ k 2 - P , N -Ph 2 PCH 2 P(N- p -C 5 F 4 N)Ph 2 }][SbF 6 ] ( 4a – f ). The catalytic activity of complexes 3 and 4 in transfer hydrogenation of cyclohexanone by propan-2-ol has been studied. Among them, the cationic derivative [Ru(η 6 -C 6 Me 6 )Cl{ k 2 - P , N -Ph 2 PCH 2 P(N- p -C 5 F 4 N)Ph 2 }][SbF 6 ] ( 4f ) shows the highest activity. Electrochemical data for 3 and 4 are also reported.

Highly Enantioselective Hydrogenation of 1-Alkylvinyl Benzoates: A Simple, Nonenzymatic Access to Chiral 2-Alkanols

Going chiral! Highly enantioselective catalytic hydrogenations of enol esters 1 by using a Rh catalyst bearing a P-OP ligand are described (see scheme; NBD=norbornadiene). The catalytic system has a broad scope and allows the preparation of a wide range of chiral esters 2 bearing diverse alkyls or a benzyl group with high enantioselectivities. These esters can easily be converted in highly enantioenriched 2-alkanols.

Ruthenium-catalyzed intermolecular [2+2+2] alkyne cyclotrimerization in aqueous media under microwave irradiation

Abstract The ability of the bis(allyl)-ruthenium(IV) complex [{RuCl(µ-Cl)(η3: η3-C10H16)}2] (C10H16=2,7-dimethylocta-2,6-diene-1,8-diyl) to promote intermolecular [2+2+2] alkyne cyclotrimerization reactions in aqueous media under microwave (MW) irradiation has been evaluated. Advantages and disadvantages of using MW vs. conventional thermal heating are discussed.

Ru(IV)-catalyzed isomerization of allylamines in water: A highly efficient procedure for the deprotection of N-allylic amines

A general and efficient method for the deprotection of N-allylic substrates in aqueous media, using catalytic amounts of the bis(allyl)-ruthenium(IV) complexes [Ru(eta3:eta2:eta3-C12H18)Cl2] and [{Ru(eta3:eta3-C10H16)(micro-Cl)Cl}2], has been developed.

Reactivity of the dimer [{Ru(η3:η3-C10H16)(μ-Cl)Cl}2] towards diphosphines and diphosphine-monoxides: synthesis and characterization of novel (2,7-dimethylocta-2,6-diene-1,8-diyl)-ruthenium(IV) complexes

Abstract Treatment of complex [Ru(η3:η3-C10H16)Cl2(κ1-P-Ph2PCH2PPh2)] (2) with AgBF4 yields the chelate derivative [Ru(η3:η3-C10H16)Cl(κ2-P,P-Ph2PCH2PPh2)][BF4] (3). Attempts to generate species structurally related to 2 by reaction of the bis(allyl)-ruthenium(IV) dimer [{Ru(η3:η3-C10H16)(μ-Cl)Cl}2] (1) with diphosphines Ph2P(CH2)nPPh2 (n=2, 3, 4) failed, obtaining instead the dinuclear compounds [{Ru(η3:η3-C10H16)Cl2}2{μ-Ph2P(CH2)nPPh2}] (n=2 (4a), 3 (4b), 4 (4c)). In contrast, mononuclear neutral species [Ru(η3:η3-C10H16)Cl2{κ1-P-Ph2P(CH2)nP(O)Ph2}] (n=1 (5a), 2 (5b), 3 (5c), 4 (5d)) have been easily prepared by reaction of 1 with the corresponding diphosphine-monoxide Ph2P(CH2)nP(O)Ph2 (n=1, 2, 3, 4). Treatment of 5a,b with AgBF4 allows the formation of cationic derivatives [Ru(η3:η3-C10H16)Cl{κ2-P,O-Ph2P(CH2)nP(O)Ph2}][BF4] (n=1 (6a), 2 (6b)).