Ruthenium amines with aqueous

Keeping this in mind, in this paper, we have studied the kinetic details of the interaction of our chosen complex (an aqua-amine complex of ruthenium(II)) with an S-containing amino acid DL-methionine at pH 7.4 in aqueous medium and a plausible mechanism is proposed. 

Judicious selection of catalyst is necessary to avoid multi-allqrlation ruthenium catalysts tend to provide primary amines from ammonia, while iridium catalysts tend to provide seeondary or tertiary amines (Scheme 12.3). The reasons for the mono-allqrlation seleetivity of ruthenium catalysts have not been thoroughly studied however, Vogt reports that extended reaction times aetually increase the seleetivity for primary amine formation. This observation points toward the reversibility of secondary imine formation, wherein hydrolysis of the seeondary imine is favoured over hydrogenation to the seeondary amine. Both iridium and ruthenium catalysts have proven to be effeetive with aqueous ammonia. 

The ruthenium tetroxide dioxide catalytic system is effective for the oxidation of alkanols, although it will also react with any alkene groups or amine substituents that are present. The catalyst can be used in aqueous acetonitrile containing tetra-butylammonium hydroxide with platinum electrodes in an undivided cell Primary alcohols are oxidised to the aldehyde and secondary alcohols to the ketone [30]. Anodic oxidation of ruthenium dioxide generates the tetroxide, which is the effective oxidising agent. 

The latter, on reaction with methylamine yielded via the P-epoxide 373, the trans-a aminoalcohol 374, which was N-acylated to the amide 375. Acid-catalysed dehydration of the tertiary alcohol 375, led to the olefin 375, from which the key radical precursor, the chlorothioether377 was secured in quantitative yield by reaction with N-chlorosuccinimide. In keeping with the earlier results recorded for structurally related compounds, 377 on heating in the presence of ruthenium dichloride and triphenylphosphine also underwent a 5-exo radical addition to generate the cyclohexyl radical 378 which recaptured the chlorine atom to furnish the a-chloro-c/5-hydroindolone 379. Oxidation of thioether 379 gave the corresponding sulfoxide 380, which on successive treatment with trifluoroacetic anhydride and aqueous bicarbonate led to the chloro-a-ketoamide 381. The olefin 382 resulting from base induced dehydrochlorination of 381, was reduced to the hydroxy-amine 383, which was obtained as the sole diastereoisomer... 

RCH2NH2 —> RCONH2The transformation of primary amines to amides can be effected by oxidation of N-Boc alkylamines with ruthenium tetroxide, generated in situ from Ru02 (catalytic) and NaI04 (excess) in aqueous ethyl acetate. Deprotection is effected with TFA in CH2C12. 

Olefin isomerization catalyzed by ruthenium alkylidene complexes can be applied to the deprotection of allyl ethers, allyl amines, and synthesis of cyclic enol ethers by the sequential reaction of RCM and olefin isomerization. Treatment of 70 with allyl ether affords corresponding vinyl ether, which is subsequently converted into alcohol with an aqueous HCl solution (Eq. 12.37) [44]. In contrast, the allylic chain was substituted at the Cl position, and allyl ether 94 was converted to the corresponding homoallylic 95 (Eq. 12.38). The corresponding enamines were formed by the reaction of 70 with allylamines [44, 45]. Selective deprotection of the allylamines in the presence of allyl ethers by 69 has been observed (Eq. 12.39), which is comparable with the Jt-allyl palladium deallylation methodology. This selectivity was attributed to the ability of the lone pair of the nitrogen atom to conjugate with a new double bond of the enamine intermediate. 

If water is present, in the presence of a ruthenium catalysr or a platinum catalyst,the addition of a primary or secondary amine to a nitrile gives an amide RCN + R NHR + H2O RCONR R + NH3 (R may be H). When benzonitrile reacts with H2P03Se in aqueous methanol, a selenoamide, PhC=Se)NH2, is formed after treatment with aq. potassium carbonate." ... 

The results of catalysis with primary and secondary amines indicate that ruthenium carbonyl forms active catalysts in aqueous ethylenediamines, diethanolamine, pyrrolidine and piperidine solutions. No detectable amounts of hydrogen are formed with aromatic and unsaturated primary and secondary amines under the present WGS conditions. Tertiary amines were found not to initiate catalyst systems as active as those produced by the best primary and secondary amines. Aliphatic tertiary amines exhibited only weak activity. 

---