Aminoalkenes asymmetric hydroamination

While hydroamination catalysts based on transition metals have been studied intensively over the past two decades, only a limited number of reports on alkali metal based hydroamination catalysts have emerged, although the first reports date back 60 years [71]. In particular, the application of chiral alkali metal complexes in asymmetric hydroamination of nonactivated aminoalkenes has drawn little attention to date [72, 73]. Also, attempts to perform asymmetric hydroamination utilizing... 

Scheme 11.12 Lithium catalyzed asymmetric hydroamination/cyclization of aminoalkenes [72, 76],...

Tire first chiral group 4 metal catalyst system for asymmetric hydroamination/ cyclization of aminoalkenes was based on the cationic aminophenolate complex (S) 45 [85[. Secondary aminoalkenes reacted readily to yield hydroamination products with enantioselectivities of up to 82% ee (Scheme 11.14). For catalyst solubility reasons, reactions were commonly performed at 100 °G in bromobenzene using... 

Equation 11.8. Organocatalytic asymmetric hydroamination/cyclization ofa sec ondary aminoalkene [111]. 

Rare earth metal complexes witii stericaUy demanding tris(aryl)silyl-substituted binaphtholate ligands efficiently catalyze asymmetric hydroamination/cyclization of aminoalkenes and the kinetic resolution of a-substituted aminopentenes. The catalytic activities are comparable to... 

Scheme 17 Catalytic asymmetric hydroamination/cyclization of aminoalkenes...

Chiral binaphtholate yttrium aryl complexes were highly active and enantiose-lective catalysts for asymmetric hydroamination of aminoalkenes as well as kinetic... 

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

Fig. 15 Selected examples of post-metallocene rare earth metal catalysts for asymmetric hydroamination/cyclization of aminoalkenes [67, 121, 219, 220, 225, 227, 230, 233, 238, 239]...

Fig. 17 Chiral lithium-based catalysts for asymmetric hydroaminations of aminoalkenes [135, 241]...

Similar to alkali metals, only few chiral alkaline earth metal complexes have been apphed in asymmetric hydroaminations of nonactivated aminoalkenes [155, 244—248] and one of the greatest challenges has been the development of a chiral catalyst system that can resist facile ligand redistribution processes leading to achiral catalytically active species. Therefore, it is not too surprising that many systems are plagued with low enantioselectivities (Fig. 18, Table 18). 

Asymmetric hydroamination of aminoalkenes catalyzed by binaphtholate tantalum complexes, e.g., 80 (Fig. 20), was reported recently [258]. Enantioselectivities of up... 

Fig. 20 Selected group 5 metal catalysts for asymmetric hydroamination of aminoalkenes (Mes = 2,4,6-Me3C6H2) [258, 259]...

Fig. 20 Important postmetallocene catalysts for asymmetric aminoalkene hydroamination/...

Ogata T, Ujihara A, Tsuchida S, Shimizu T, Kaneshige A, Tomioka K. Catalytic asymmetric intramolecular hydroamination of aminoalkenes. Tetrahedron Lett. 2007 48(38) 6648-6650. 

Table 15 Asymmetric intramolecular hydroamination of aminoalkenes with a secondary amino group using post-metallocene rare earth metal catalysts...

The proUne-derived diamidobinaphthyl dilithium salt S,S,S)-66, which is dimeric in the sohd state and can be prepared via deprotonation of the corresponding tetraamine with n-BuLi, represents the first example of a chiral main-group-metal-based catalyst for asymmetric intramolecular hydroamination reactions of aminoalkenes [241], The unique reactivity of (S,S,S)-66, (Fig. 17) which allowed reactions at or below ambient temperatures with product enantioselec-tivities of up to 85% ee (Table 17) [241, 243] is believed to derive from the close proximity of the two lithium centers chelated by the proline-derived substituents. More simple chiral lithium amides required significantly higher reaction temperatures and gave inferior selectivities. 

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