Vinyl arenes, intermolecular hydroamination

The well-defined copper complexes 94 and 95 (Fig. 2.16) have been used as catalysts for the intermolecular hydroamination of electron-deficient alkenes [Michael acceptors, X=CN, C(=0)Me, C(=0)(0Me)] and vinyl arenes substituted... 

Table 7 Bi(OTf)3/Cu(CH3CN)4PF6-catalyzed intermolecular hydroamination of vinyl arenes...

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... 

Multiple efficient catalysts were reported for the intramolecular process, while the intermolecular process has been studied predominantly for alkynes. The reactivity of the unsaturated fragment decreases in the order alkyne > allene diene > vinyl arene unactivated alkene with the intermolecular hydroamination of simple alkenes representing the most difficult transformation. The hydroamination of all types of carbon-carbon unsaturated fragments will be covered in this chapter. 

The intermolecular hydroamination is significantly less feasible than the intramolecular process as the C-C unsaturated moiety is not tethered in the vicinity of the catalytic center. The mechanism is believed to be analogous to the intramolecular case, with insertion being less favorable [20]. The insertion step was identified to be rate limiting in the intermolecular lithium-amide-catalyzed hydroamination of vinyl arenes by detailed DFT-analysis [40]. 

---