Ruthenium catalysts amination

Hydrogenation of amides normally result in the formation of alcohols, whereas lactams give cyclic amines. The work presented in this paper is the first example that we are aware in which a lactam was hydrogenated by a ruthenium catalyst. To verify that acid promoted the lactam carbonyl hydrogenation, two... 

The ruthenium-catalyzed isomerization of aryl allyl ethers or amines followed by ring-closing metathesis with ruthenium catalyst 1 furnishes fused benzo-heterocycles in good yield (Scheme 40).66 67... 

Scheme 2.26 DKR of chiral amines using CALB and a ruthenium catalyst.

In 1989, a method for the peroxysilylation of alkenes nsing triethylsUane and oxygen was reported by Isayama and Mnkaiyama (eqnation 25). The reaction was catalyzed by several cobalt(II)-diketonato complexes. With the best catalyst Co(modp)2 [bis(l-morpholinocarbamoyl-4,4-dunethyl-l,3-pentanedionato)cobalt(n)] prodnct yields ranged between 75 and 99%. DiaUcyl peroxides can also be obtained starting from tertiary amines 87, amides 89 or lactams via selective oxidation in the a-position of the Af-fnnctional group with tert-butyl hydroperoxide in the presence of a ruthenium catalyst as presented by Murahashi and coworkers in 1988 ° (Scheme 38). With tertiary amines 87 as substrates the yields of the dialkyl peroxide products 88 ranged between 65 and 96%, while the amides 89 depicted in Scheme 38 are converted to the corresponding peroxides 90 in yields of 87% (R = Me) and 77% (R = Ph). 

Phenyl selenides.2 In the presence of a ruthenium catalyst, prepared by reaction of RuCly with 3 equivalents of potassium, lithium benzencselenolate reacts with a wide variety of tertiary amines to form phenyl selenides in excellent yield. Anhydrous diglyme is used as solvent. 

The application of various ruthenium compounds in acetonitrile330 or rhodium and ruthenium catalysts or their mixtures331 was found to show significant improvements (high product selectivities, high linearities) in the aminomethylation of terminal alkenes to produce tertiary amines. 

Since many ruthenium species, including ammines, are readily carbonyl-ated using carbon monoxide under mild conditions (4, 5), there seemed a good probability that effective ruthenium catalysts could be found for amine carbonylation under mild conditions. Product selectivity, a problem at more severe conditions, should also improve. 

Other Ruthenium Catalysts. Ru3(CO)i2 readily dissolved in piperidine to give a solution effective for catalytic carbonylation of the amine. The uptake plots resemble those shown in Figure 1 (curves B-E), and the maximum rate given in Table I refers to the initial rate. Attempts to characterize the ruthenium complexes formed from reaction of the dodecacarbonyl with amines have been unsuccessful. 

N-Heterocyclization.1 1,5-Pentanediol reacts with primary amines at 150-180° in the presence of a ruthenium catalyst to form N-substituted piperidines. For the reaction with aromatic amines RuC I QHs) is the catalyst of choice. On the other hand, the most effective catalyst for the reaction with aliphatic amines is RuC13 combined with either tributylphosphine or triethylphosphine. 

In Section 6.3.6, it was emphasized that C02 and secondary amines could add to terminal alkynes in the presence of ruthenium catalysts to afford carbamates. Under comparable conditions (393-413 K, 5 MPa Ru-catalysts), primary amines will afford symmetrical disubstituted ureas in moderate yield [131]. It is worth noting that although the final urea does not contain the starting alkyne, its catalytic formation requires, besides the Ru-catalyst, the presence of a stoichiometric amount of a 1-alkyne (e.g., a propargylic alcohol). A possible mechanism (Scheme 6.32) for this catalytic reaction may involve activation of the alkyne at the metal center, a nucleophilic addition of the carbamate to the activated alkyne to produce... 

Unsymmetrical secondary and tertiary amines. Unsymmetrical amines are obtained in 50-95% yield by reaction of an alcohol and amine in the presence of this ruthenium catalyst. The intramolecular version of this reaction provides an efficient synthesis of cyclic amines either from oc,a>-amino alcohols and an alcohol or from a,tu-diols and an amine. The cyclization is useful for preparation of tetrahydroiso-quinolines.3... 

Ammonium carbamates are readily and reversibly produced on reaction of secondary amines with carbon dioxide. In the presence of a ruthenium catalyst precursors such as Ru3(CO)12 [3], (arene)RuCl2(PR3) [4] or Ru(methallyl)2(dppe) [5] (dppe=bis(diphenylphosphino)ethane) complexes, the three-component combination of a secondary amine, a terminal alkyne, and carbon dioxide selectively provides vinylcarbamates resulting from addition of carbamate to the terminal carbon of the triple bond (Scheme 2). 

The homogeneous catalytic asymmetric hydrogenations of 2-arylacrylic acids have been studied. Both rhodium and ruthenium catalysts have been examined. The reaction temperatures and hydrogen pressures have profound effects on the optical yields of the the products. The presence of a tertiary amine such as triethylamine also significantly increases the product enantiomer excess. Commercially feasible processes for the production of naproxen and S-ibuprofen have been developed based on these reactions. 

Stephenson and coworkers applied reductive photoredox catalysis to trigger radical 6-exo cyclizations of co-pyrrole or co-indole-substituted a-bromocarbonyl compounds 124 [186] as well as radical 5-exo cyclizations of 2-bromo-2-(4-pentenyl)malonates 126 (Fig. 32) [187]. These cyclization processes provide bi- or tricyclic products 125 or cyclopentanecarboxylates 127 in moderate to excellent yields. The initial radical was formed with reduced ruthenium catalyst HOB generated similarly as above from 110 and a sacrificial amine... 

Most ruthenium catalysts used in epoxidation reactions are based on bulky porphyrins or other amine ligands and require the use of PhIO and Cl2PyNO as oxidants. For examples see the reviews in Refs. [5,6,45] and some recent examples by Liu and coworkers [46,47] and Jitsukawa et al. [48]. Examples for the aerobic epoxidation of alkenes are the ruthenium mesityl porphyrin complex Ru(TMP)(0)2, where TMP is 5,10,15,20-tetramesitylporphyrinato, of Groves and Quinn [12] in 1985 (Eq. 7), the ruthenium dimethylphenanthroline complex, czs-[Ru(2,9-dimethyl-l,10-phenanthroline)(CH3CN)2]2+ published by Goldstein et al. [23] in 1994 (Eq. 8), and the ruthenium POM catalyst [WZnRu2(0H)(H20)](ZnW9034)2 n of Neumann and Dahan [49] in 1997 (Eq. 9). 

Table 7 Oxidation of primary and secondary amines using heterogeneous ruthenium catalysts with molecular oxygen...

Since ruthenium catalysts were shown to be highly active and selective for the hydrogenation of aromatic amines by Behr et al.,186a Whitman,186b and Barkdoll et al.,93 the usefulness of ruthenium as hydrogenation catalysts has been recognized by many... 

TABLE 11.17 Effects of Solvents on Hydrogenation-Hydrogenolysis of Aromatic Amines over Ruthenium Catalyst ... 

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