Hydroamination rhodium catalyst

The intramolecular anti-Markovnikov hydroamination of l-(3-aminopropyl)vinyl-arenes (71 R = H, Me, CH2OMe, CH2OTBS) in the presence of a rhodium catalyst to form 3-arylpiperidines (72) has been reported. In contrast to intermolecular hydroamination of vinylarenes, which occurs in high yields in the presence of rhodium catalysts... 

Rhodium catalysts have also found application in oxidative aminations of styrenes. Beller and co-workers observed that numerous styrenes reacted with various kinds of secondary aliphatic amines in the presence of the cationic rhodium complexe [Rh(cod)2]BF4 and PPhs. Regioselectively the corresponding anti-Markovnikov products ( -enamines) were formed [49], While the Markovnikov product was never observed under such conditions, the target enamine was mostly obtained along with hydrogenated olefin, and in some cases even small amounts of hydroaminated products were detected [50],... 

The Rh and Ir complexes 85-88 (Fig. 2.14) have been tested for the intramolecular hydroamination/cyclisation of 4-pentyn-l-amine to 2-methyl-1-pyrroline (n = 1). The reactions were carried out at 60°C (1-1.5 mol%) in THF or CDCI3 The analogous rhodium systems were more active. Furthermore, the activity of 87 is higher than 85 under the same conditions, which was attributed to the hemilabihty of the P donor in the former complex, or to differences in the trans-eSects of the phosphine and NHC ligands, which may increase the lability of the coordinated CO in the pre-catalyst [75,76]. 

The first transition metal-catalyzed hydroamination of an olefin was reported in 1971 by Coulson who used rhodium(I), rhodium(III) or iridium(III) catalysts (Eq. 4.8) [105,106]. 

Study of the mechanism of the rhodium-catalyzed hydroamination of ethylene with secondary amines indicated that the piperidine complex trans-RhCl(C2H4)(piperidine)2 can serve as a catalyst precursor [109, 110]. 

It was elegantly shown later that the hydroamination of ethylene with piperidine or Et2NH can be greatly improved using cationic rhodium complexes at room temperature and atmospheric pressure to afford a high yield of hydroaminated products (Eq. 4.10) [111]. However, possible deactivation of the catalyst can be questioned [17]. 

Although the hydroamination of Michael systems is beyond the scope of this review, it is interesting to note the high yield (98%, TOE = 2 h ) obtained using the above cationic rhodium complexes for the hydroamination of 2-vinylpyridine with morpholine. Indeed, without catalyst, the hydroamination yield is only 5% [167]. 

A range of rhodium complexes have been studied as hydroamination catalysts. Treatment of norbornene with a mixture of aniline and lithium anilide in the presence of [Rh(PEt3)2Cl]2 at 70 °C for over 1 week yields the exo addition product in ca. 15% yield.165... 

Table 13 Rhodium-catalvzed hydroamination of terminal alkynes with anilines (catalyst system = fRh-...

The use of catalytic SILP materials has been reviewed recently [10] covering Friedel-Crafts reactions [33-37], hydroformylations (Rh-catalyzed) [38], hydrogenation (Rh-catalyzed) [39,40], Heck reactions (Pd-catalyzed) [41], and hydroaminations (Rh-, Pd-, and Zn-catalyzed) [42]. Since then, the SILP concept has been extended to additional catalytic reactions and alternative support materials. In this paper we will present results from continuous, fixed-bed carbonylation and hydroformylation reactions using rhodium-based SILP catalysts as reaction examples demonstrating the advantages of the SILP technology for bulk chemical production. 

Optimized reaction conditions call for the use of Wilkinson s catalyst in conjunction with the organocatalyst 2-amino-3-picoline (60) and a Br0nsted add. Jun and coworkers have demonstrated the effectiveness of this catalyst mixture for a number of reactions induding hydroacylation and C—H bond fundionalization [25]. Whereas, in most cases, the Lewis basic pyridyl nitrogen of the cocatalyst ads to dired the insertion of rhodium into a bond of interest, in this case the opposite is true - the pyridyl nitrogen direds the attack of cocatalyst onto an organorhodium spedes (Scheme 9.11). Hydroamination of the vinylidene complex 61 by 3-amino-2-picoline gives the chelated amino-carbene complex 62, which is in equilibrium with a-bound hydrido-rhodium tautomers 63 and 64. 

Hydroamination of allenes and 1,3-dienes in the presence of Ni(II), Pd(II), and Rh(III) complexes yields product mixtures composed of simple addition products and products formed by addition and telomerization.288 Nickel halides308 and rhodium chloride309 in ethanol [Eq. (6.51)] and Pd(n) diphosphine complexes310 are the most selective catalysts in simple hydroamination, while phosphine complexes favor telomerization 288... 

The aziridination of olefins, which forms a three-membered nitrogen heterocycle, is one important nitrene transfer reaction. Aziridination shows an advantage over the more classic olefin hydroamination reaction in some syntheses because the three-membered ring that is formed can be further modified. More recently, intramolecular amidation and intermolecular amination of C-H bonds into new C-N bonds has been developed with various metal catalysts. When compared with conventional substitution or nucleophilic addition routes, the direct formation of C-N bonds from C-H bonds reduces the number of synthetic steps and improves overall efficiency.2 After early work on iron, manganese, and copper,6 Muller, Dauban, Dodd, Du Bois, and others developed different dirhodium carboxylate catalyst systems that catalyze C-N bond formation starting from nitrene precursors,7 while Che studied a ruthenium porphyrin catalyst system extensively.8 The rhodium and ruthenium systems are... 

A series of rhodium and platinum compounds have been tested in the hydroamination of norbomene with aniline, as shown in Scheme 9.36.[141] Selectivity and activity were highly dependent on the nature of the ionic liquid, but were always superior to those observed in THF. Solvents with chloride anions led to essentially no catalytic activity, whereas [PF6] or Br afforded some catalysis. Nonetheless, even with the best solvent/catalyst combination, less than 40 turnovers are achieved after 6 days at 140°C. 

As the first transition metal-based homogeneous catalysis of hydroamination, in the early 1970s Coulson from the Du Pont laboratories had described the addition of secondary aliphatic amines to ethylene in the presence of various rhodium compounds [15, 16]. Definite results were reported with RhCl3 3 H2O as pre-catalyst in tetrahydrofuran as solvent under starting ethylene pressures of 5-14 MPa at 180-200 °C for different secondary amines (Table 3). 

Quite stable catalytic reaction solutions were obtained in THF with the starting pressure for ethylene of 6-6.5 MPa at a reaction temperature of 120 °C. Under these conditions and with the ratios piperidine/rhodium of 100 1 and 1000 1 in 36 and 72 h, yields of 70 and 50 % ethylpiperidine were reached, which correspond to TONs of 2 and 7 mol amine/(mol Rh) per h, respectively. Total conversion is also possible if the reaction time is prolonged further. As a side reaction, ethylene dimerization to butene was observed. This indicates the formation of a hydrido rhodium(III) complex in the hydroamination reaction, as formulated in Scheme 3, route (b). Hydrido rhodium(III) complexes are known as catalysts for ethylene dimerization [19], and if the reductive elimination of ethylpiperidine from the hydrido-y9-aminoethyl rhodium(III) complex is the rate-limiting step in the catalytic cycle of hydroamination, a competitive catalysis of the ethylene dimerization seems possible. In the context of these mechanistic considerations, an increase of the catalytic activity for hydroamination requires as much facilitation of the reductive elimination step as possible. 

Ebrahimi, D., Kennedy, D. F., Messerle, B. A. Hibbert, D. B. (2008). High throughput screening arrays of rhodium and iridium complexes as catalysts for intramolecular hydroamination using parallel factor analysis. Analyst, Vol. 133,... 

Alkyne hydroamination has been extensively reviewed [3, 4, 10] and important contributions using late transition metals have been realized to give the Markovnikov-type products most typically. Interestingly, in 2007, Fukumoto reported a tris(pyrazolyl borate)rhodium(l) complex for the anti-Markovnikov hydroamination of terminal aUcynes with both primary and secondary amine substrates, although yields with primary amines are always reduced compared to those with secondary amines (Scheme 15.26). Desirable functional group tolerance is also noteworthy for this regioselective hydroamination catalyst [187]. 

Several metal complexes with CCC pincer-type dicarbene ligands have been investigated over the years by the group of Hollis as catalysts for the intramolecular hydroamination/cychzation of unactivated alkenylamines. Initial studies concerned rhodium(III) and iridium(III) complexes of type 75, but later investigations were extended to complexes of the same ligands with group 4 metals such as zirconium, hafnium, and tita-... 

Field LD, Messerle BA, Vuong KQ, Turner P. Rhodium(I) and iridium(I) complexes containing bidentate phosphine-imidazolyl donor ligands as catalysts for the hydroamination and hydrothiolation of alkynes. Dalton Trans. 2009 3599-3614. 

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