Kinetic studies hydroamination

Kinetic studies in the intramolecular hydroamination/cyclization reaction show first order dependence on the precatalyst and zero order dependence on the substrate, making the kinetic rate law as described in 14 [104]. 

Kinetic studies of the hydroamination of styrene with pyrrolidine catalyzed by 32 revealed an empirical rate law V = [styrene] [pyrrolidine] °[32] °. A strong kinetic isotope effect was observed in the reaction of styrene with A-deuterated pyrrolidine catalyzed by 32 = 6.8 and 7.3 at 40 and 60 °C respectively). These results were conciliated... 

In 1999, Doye disclosed that dimethyltitanocene is a catalyst widely applicable to intermolecular hydroamination of alkynes with primary aryl- and alkylamines [302]. In the case of unsymmetrically substituted alkynes, the reaction occurs with high re-gioselectivity, forming the anti-Markovnikov products exclusively (Scheme 14.127). Kinetic studies suggest that the reaction mechanism involves the formation of a Ti-imido complex as the catalytically active species. Doye further developed a tandem Ti-catalyzed protocol of alkyne hydroamination and imine reduction, affording secondary amines in a fully catalytic one-pot reaction [303]. 

Kinetic studies conducted upon the reaction of styrene with piperidene catalyzed by [Sr N(SiMe3)2 2l demonstrated that the reaction follows the empirically determined rate law v = obs[amine] [alkene] [catalyst] [98]. A similar second-order dependence on catalyst has been observed for related solvent-free homoleptic group 2 amides in intramolecular hydroamination catalysis (see Sect. 2.1.1) [82]. While monitoring the reaction rate as a function of initial amine concentration revealed that saturation occurs at higher amine concentrations, a large primary KIE was observed for this reaction taking values of 4.3(343 K) and 4.1(348 K) for calcium and 7.9(348 K) for strontium (Fig. 4). The latter value represents an extremely large primary KIE when compared to the maximum calculated value of 8.5 (for a N-H vibration at 3,100 cm ) [98]. 

A kinetic study of intermolecular hydroamination of allylic amines by N-alkylhydroxylamines has revealed a first-order dependence on aldehyde catalyst. 

The experiments illustrated in Eqs. (6) and (7) clearly indicate that the reaction proceeds in an irreversible and direct manner. (1) In Eq. (6), the coexistent hydroamination adduct 29 afforded neither free styrene nor crossover products, indicating that the hydroamination is an irreversible process. (2) In the reaction of 2,5-dimethylstyrene (27) with morphorine (28) in Eq. (7), an additive, Markovnikov-type adduct 31, did not isomerize to anti-Markovnikov-type adduct. (3) The kinetic study on the amination process revealed a large negative of —213 J mol s , which is similar to the value of the nitroalkene amination. The first-order rate constant of the arene exchange process is comparable to that of the amination process. (4) The conjugate addition nature was confirmed by using... 

The formation of alkyne oligomers that are concomitantly formed in the hydroamination reactions catalyzed by the thorium complexes indicates that two possible different complexes can be considered as active, conceivably with inter-conversion causing the occurrence of the two parallel processes. The discernment between these two most probable mechanistic pathways to find the key organometallic intermediate, responsible for the hydroamination process, was achieved by kinetic and thermodynamic studies (Scheme 5). The first pathway proposed the insertion of an alkyne into a metal-imido (M=N) bond, as observed for early transition metal complexes [101]. The second pathway suggested the insertion of an alkyne into a metal-amido bond, as found in some lanthanide compounds [39, 58, 84, 85]... 

G. A. Khger, L. S. Glebov, R. A. Fridman, E. I. Bogolepova, and A. N. Bashkirov [Kinet. Catal., 19, 489 (1978)] studied the kinetics of the hydroamination of 2-octanone and other aliphatic ketones over a sintered iron catalyst ... 

General aspects of this reactivity,including theoretical studies,have been reviewed. Particular attention has been paid to reactions with amines to get more information on metal-catalyzed hydroamination of alkenes. A recent DFT theoretical study has evaluated the hydroamination process for different metals, concluding that nucleophilic attack of amine is thermodynamically and kinetically favorable for group 10 metals. " ... 

Reznichenko AL, Hampel F, Hultzsch KC. Kinetic resolution of aminoalkenes by asymmetric hydroamination a mechanistic study. Chem. Eur. J. 2009 15(46) 12819-12827. 

Iridium The intermolecular hydroamination of unactivated C=C bonds in ct-olefins (RCH=CH2) and bicycloalkenes (norbornene and norbornadiene) with arylamides (ArCONH2) and sulfonamides has been attained upon catalysis by chiral iridium complexes (PP)IrHCl(NHCOAr)(NH2COAr) [PP = chiral bidentate diphosphine]. Mechanistic studies identified the product of N-H bond oxidative addition and coordination of the amide as the resting state of the catalyst. Rapid, reversible dissociation of the amide precedes reaction with the alkene, but an intramolecular, kinetically significant rearrangement of the species occurs before the reaction with alkene. ... 

The mechanism of the group 4 metal-catalyzed hydroamination of alkynes (Scheme 4) and allenes has been thoroughly investigated in detailed kinetic and mechanistic [41 6] as well as computational studies [47, 48]. The catalytically active species is believed to be a metal imido complex, which undergoes a reversible, rate-determining [2 + 2]-cycloaddition with an alkyne, respective allene, to yield an azametallacyclobutene species. Subsequent protonolysis leads to the imine hydroamination product. Isolation and characterization of intermediate azacyclobutene species, which are catalytically competent themselves, is a strong support of the mechanism [41,43,49-51]. Although no direct experimental [52, 53]... 

The asymmetric hydroamination/cyclization of aminostilbenes has been studied utilizing chiral bisoxazoline lithium catalysts [242] and enantioselectivities reaching as high as 91% ee were achieved (Scheme 16). The reactions were performed in toluene at —60°C to give the exo-cyclization product 69 under kinetic control. However, the hydroamination/cychzation reaction in THF solution is reversible, producing the thermodynamically favored e z/o-cychzation product 70 when the reaction time was extended to 24 h. 

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