Rhodium , hydrolysis

Rhodium, iodotetrakis(difluoro(diethylamino)-phosphine)-, 4, 924 Rhodium, pentaamminethiocyanato-base hydrolysis, 1, 504 Rhodium, pentaammincurea-linkage isomerism, 4, 961 Rhodium, pentaammine(urea)-decomposition, 1,186... 

Allyl groups attached directly to amine or amide nitrogen can be removed by isomerization and hydrolysis.228 These reactions are analogous to those used to cleave allylic ethers (see p. 266). Catalysts that have been found to be effective include Wilkinson s catalyst,229 other rhodium catalysts,230 and iron pentacarbonyl.45 Treatment of /V-allyl amines with Pd(PPh3)4 and (V,(V -dimethylbarbi Lurie acid also cleaves the allyl group.231... 

Different reactions pathways on Rh may explain the intermediate formation of ammonia. NH3 can be obtained via successive reaction steps between adsorbed NHX and dissociated hydrogen species [29]. Alternately, the formation of ammonia may occur via the hydrolysis of isocyanic acid (HNCO) [30]. Isocyanate species are formed by reaction between N and COads on metallic particles. Those species can diffuse onto the support leading to spectator species or alternately react with Hads yielding ultimately HNCO. Previous infrared spectroscopic investigations pointed out that isocyanate species predominantly form over rhodium-based catalysts [31]. 

Complexation of (124) and (125) with [ Rh(COD)Cl 2] in the presence of Si(OEt)4, followed by sol-gel hydrolysis condensation, afforded new catalytic chiral hybrid material. The catalytic activities and selectivities of these solid materials have been studied in the asymmetric hydro-gen-transfer reduction of prochiral ketones and compared to that of the homogeneous rhodium complexes containing the same ligands (124) and (125) 307... 

The groups of Loupy and Jun have presented a chelation-assisted rhodium(I)-cata-lyzed ortho-alkylation of aromatic imines with alkenes (Scheme 6.57) [119]. The use of 2 mol% of Wilkinson s catalyst, RhCl(PPh3)3, and 5 equivalents of the corresponding alkene under solvent-free conditions proved to be optimal, providing the desired ortho-alkylated ketones in high yields after acidic hydrolysis. Somewhat lower yields were obtained when the imine preparation and the ortho-alkylation were realized in a one-pot procedure. 

A complex naturally occurring amino acid 5-hydroxypiperazic acid (5HyPip) 100 was prepared by a multistep procedure that included Diels-Alder addition of 2,4-pentadienoic acid to phthalazinedione 83a as a first step (Scheme 24). Adduct 97 was esterified and oxidized with mercuric acetate to 98, which on hydrogenation over rhodium on alumina and subsequent hydrolysis provided a mixture of enantiomers from which the required enantiomer 99 was obtained by resolution with quinine. Its hydrazinolysis provided 100 [71JCS(C)514 77H119],... 

Menthone and camphor undergo asymmetric hydrosilylation to give alkoxysilanes with up to 82% optical purity using neutral rhodium(I) catalysts containing DIOP or neomenthyl- or menthyl-diphenylphos-phine even triphenylphosphine gave about 65% ee (300). Hydrolysis to alcohols was not reported. The ferrocenyl ligands (28, 29) are similarly effective for asymmetric hydrosilylation (255), and could be used for production of the optically active alcohols. 

The most efficient way to produce optically active amines, at least with a rhodium-DIOP catalyst, is via the hydrosilylation-hydrolysis process (229, 284, Chapter 9 in this volume) for example ... 

However, on a lightly cross-linked hydroxyethylmethacrylate/styrene polymer that swells in polar solvents (22, 365), or on a silica-gel support (366), catalyst performance matches that of the soluble one for the precursor amino acid substrates. A rhodium-DIOP analog has also been supported on a polymer containing pendent optically active alcohol sites [incidentally, formed via hydrosilylation and hydrolysis of a ketonic polymer component using an in situ rhodium(I)-DIOP catalyst]. The supported catalyst in alcohol again matched that of the soluble catalyst for... 

Although the asymmetric isomerization of allylamines has been successfully accomplished by the use of a cationic rhodium(l)/BINAP complex, the corresponding reaction starting from allylic alcohols has had a limited success. In principle, the enantioselective isomerization of allylic alcohols to optically active aldehydes is more advantageous because of its high atom economy, which can eliminate the hydrolysis step of the corresponding enamines obtained by the isomerization of allylamines (Scheme 26). 

Similarly, ketimines (benzylimines of aromatic ketones) undergo the rhodium-catalyzed ortho-alkenylation with alkynes to give or/ o-alkenylated aromatic ketones after hydrolysis.61 This method is applied to an efficient one-pot synthesis of isoquinoline derivatives by using aromatic ketones, benzylamine, and alkynes under Rh catalysis (Equation (55)). 

The coordination of the alkyne to the rhodium catalyst allows the carborhodation of the triple bond to afford the vinylrhodium intermediate 47 (Scheme 14). The rearrangement of this organometallic compound into the 2-(alkenyl)phenylrhodium intermediate 48 is evidenced by one deuterium incorporation resulting from the deuter-iolysis of the Rh-C bond. The addition of the phenylrhodium intermediate 45 must occur before its hydrolysis with water. The 2-(alkenyl)phenylrhodium intermediate 45, generated by the phenylrhodation of an alkyne followed by... 

The proposed mechanism (Scheme 54) indicated that transmetallation of the aryl silanediol to the rhodium hydroxide catalyst followed by 1,4-addition and hydrolysis of the O-bound enolate generated the addition product and regenerated the Rh-OH catalyst. 

Organotrialkoxysilanes (ArSi(OR)3) were used as organometallic reagents without fluoride additives (Scheme 56).144,144a ArSi(OR)3 was easy to use because of its higher air and moisture stability. Oi and co-workers believed that hydrolysis of the trialkoxysilanes to generate silanetriols was likely occurring prior to transmetallation of the cationic rhodium complex. 

Secondary phosphine oxides are known to be excellent ligands in palladium-catalyzed coupling reactions and platinum-catalyzed nitrile hydrolysis. A series of chiral enantiopure secondary phosphine oxides 49 and 50 has been prepared and studied in the iridium-catalyzed enantioselective hydrogenation of imines [48] and in the rhodium- and iridium-catalyzed hydrogenation functionalized olefins [86]. Especially in benzyl substituted imine-hydrogenation, 49a ranks among the best ligands available in terms of ex. 

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