Intramolecular Alkene Hydroamination with Hybrid Catalysts Consisting of a Metal Salt and a Neutral Organic Base

Stegner, Philipp; Fischer, Christian; Nguyen, D. Thao; Rösch, Andreas; Penafiel, Johanne; Langer, Jens; Wiesinger, Michael; Harder, Sjoerd

doi:10.1002/ejic.202000671

Cited by 4 publications

(5 citation statements)

References 53 publications

(35 reference statements)

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“…Another type of catalysts for the enantioselective intramolecular hydroamination is based on the application of alkaline earth metals as pure Lewis-acidic metal centers. For example, non-basic calcium iodide as a Lewis acid and an external base for deprotonation can be used [ 27 , 125 ]. In general, it was found that the activities of alkaline earth metal iodides decrease in the series Ca > Sr >> Mg > Ba [ 27 ].…”

Section: Chiral Pool-based Catalysts For Asymmetric Hydroamination Re...mentioning

confidence: 99%

“…For example, non-basic calcium iodide as a Lewis acid and an external base for deprotonation can be used [ 27 , 125 ]. In general, it was found that the activities of alkaline earth metal iodides decrease in the series Ca > Sr >> Mg > Ba [ 27 ]. The proposed mechanism is shown in Figure 4 .…”

Section: Chiral Pool-based Catalysts For Asymmetric Hydroamination Re...mentioning

confidence: 99%

“…The experimentally determined ee values are generally lower than those for ( S )- 69 , which achieves enantioselectivities of a max. 33% ( Table 18 , entries 7 and 8) [ 27 ].…”

Section: Chiral Pool-based Catalysts For Asymmetric Hydroamination Re...mentioning

confidence: 99%

“… Catalytic cycle of the intramolecular hydroamination of aminoalkenes using CaI 2 as catalyst and t Bu P4 as external base [ 27 ]. …”

Section: Figures Schemes and Tablesmentioning

confidence: 99%

“…In 1971, Coulson described the reaction of amines with alkenes by using catalytic active Rh and Ir species [ 23 ]. Since then, the field of C,N coupling via hydroamination has been expanding [ 6 , 12 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Early transition metals of group IV and V from the periodic table of elements were introduced by Bergman and Livinghouse [ 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

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Jumping in the Chiral Pool: Asymmetric Hydroaminations with Early Metals

2023

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The application of early-metal-based catalysts featuring natural chiral pool motifs, such as amino acids, terpenes and alkaloids, in hydroamination reactions is discussed and compared to those beyond the chiral pool. In particular, alkaline (Li), alkaline earth (Mg, Ca), rare earth (Y, La, Nd, Sm, Lu), group IV (Ti, Zr, Hf) metal-, and tantalum-based catalytic systems are described, which in recent years improved considerably and have become more practical in their usability. Additional emphasis is directed towards their catalytic performance including yields and regio- as well as stereoselectivity in comparison with the group IV and V transition metals and more widely used rare earth metal-based catalysts.

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Section: Chiral Pool-based Catalysts For Asymmetric Hydroamination Re...mentioning

confidence: 99%

Section: Chiral Pool-based Catalysts For Asymmetric Hydroamination Re...mentioning

confidence: 99%

“…The experimentally determined ee values are generally lower than those for ( S )- 69 , which achieves enantioselectivities of a max. 33% ( Table 18 , entries 7 and 8) [ 27 ].…”

Section: Chiral Pool-based Catalysts For Asymmetric Hydroamination Re...mentioning

confidence: 99%

“… Catalytic cycle of the intramolecular hydroamination of aminoalkenes using CaI 2 as catalyst and t Bu P4 as external base [ 27 ]. …”

Section: Figures Schemes and Tablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Jumping in the Chiral Pool: Asymmetric Hydroaminations with Early Metals

2023

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Effect of Additives in the Hydroamination/Cyclization of Aminoalkenes Catalyzed by a Binaphtholate Yttrium Catalyst

2023

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A series of various solvents and additives were tested in enantioselective hydroamination/cyclization reactions of aminoalkenes catalyzed by a binaphtholate yttrium catalyst. The functional group tolerance of the catalyst and the influence on the reaction rate and enantioselectivity was studied. Some weakly coordinating polar solvents, such as Et2O, MTBE, and chlorobenzene led to slightly increased reaction rates compared to the less polar solvent benzene, presumably due to a better stabilization of the polar transition state. Stronger binding solvents and additives, such as THF, DMAP, pyrrolidine, n‐propylamine, and 1‐phenylethylamine, decrease the reaction rate and diminish the enantioselectivity of the hydroamination product. Some additives, such as THF, Et2O, MTBE, chloro‐ and bromobenzene, as well as (+)‐sparteine resulted in slightly higher enantioselectivities in the cyclization of the model substrate C‐(1‐allylcyclohexyl)methylamine, although this observation was not generally true for other aminoalkene substrates. The reaction rates and enantioselectivities were depressed in the presence of (−)‐sparteine using the (R)‐binaphtholate‐ligated catalyst. In case of C‐(1‐allylcyclohexyl)methylamine, the enantioselectivity was switched from 76% ee favoring the (S)‐enantiomer of the hydroamination product when using (+)‐sparteine to 22% ee in favor of the (R)‐enantiomer when (−)‐sparteine was used. The rates of cyclization of aminoalkenes and the resulting enantioselectivities significantly depend on substrate concentration with the highest rate (13.6 h−1) and enantioselectivity (68% ee) observed in dilute conditions (0.05 M) compared to a concentrated solution (0.5 M, 5.0 h−1, 35% ee) for 2,2‐dimethylpent‐4‐enylamine. These observations indicate that the reaction mechanism is shifted in favor of a slower, less enantioselective catalytic cycle involving a higher coordinate species when higher substrate concentrations or stronger binding additives are present.

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