Hydroamination of vinylarenes

Ruthenium complexes also catalyze the anti-Markovnikov hydroamination of vinylarenes. In this case, the combination of l,5-bis(diphenylphosphino)pentane (DPPPent), triflic acid, and a ruthenium(II) precursor generates a catalyst for the additions of secondary amines to vinylarenes (Equation 16.72). This mixture of catalyst components has been shown to generate a cationic Ti -arene complex of a PCP pincer ligand generated from the DPPPent ligand. The mechanism of this reaction involves nucleophilic attack of the amine on an Ti -vinylarene complex, as described in more detail in the section on the mechanisms of hydroamination. 

Finally, a much different catalyst, a lanthanocene, generates (3-phenethylamines from the anti-Markovnikov hydroamination of vinylarenes and primary alkylamines (Equation 16.73). These reactions occur with vinylarenes containing a range of electronic properties. The reaction is thought to occur by insertion of styrene into a lanthanum-amido complex. 

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An efficient hydroamination of vinylarenes with arylamines catalyzed by Pd complexes affords vcc-phenylethylamine products.592 The reaction requires the use of... 

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... 

A detailed mechanistic investigation revealed the steps of the anti-Markovnikov hydroamination of vinylarenes (81) with alkylamines catalysed by (COD)Ru(2-methyl-allyl)2, bis(diphenylphosphino)pentane, and TfOH. Treatment of the catalyst components with an excess of styrene under the catalytic conditions afforded a new... 

Vo, L. K. Singleton, D. A. Isotope effects and the nature of stereo- and regiose-lectivity in hydroaminations of vinylarenes catalyzed by paUadiuin(II)-diphospliine complexes, Org. Lett. 2004, 6, 2469-2472. 

By changing to Rh as the catalyticaUy active metal in combination with the large-bite-angle chelating phosphine Hgand DPEphos, anti-Markovnikov hydroamination of vinylarenes with nucleophihc secondary amines can be realized (Table 15.20)... 

Compared to the hydroamination of alkynes, the protocols for more readily available olefins were rather limited. Ackermann presented a TiCU-catalyzed hydroamination reaction of norbornene using a variety of functionalized amines. Regioselective hydroarylation occurs as a competing reaction and the chemose-lectivity for hydroamination products ranges from poor to excellent [312]. This protocol can also be utilized in the hydroamination of vinylarenes with some electron-deficient amines [313] and the hydroamination of enyne compound. In the latter reaction, a subsequent rearrangement gives rise to a tetrahydroisoquinoline derivative (Scheme 14.134). 

Kawatsura M, Hartwig JF. Palladium-catalyzed inter-molecular hydroamination of vinylarenes using arylamines. J. Am. Chem. Soc. 2000 122(39) 9546-9547. 

A totally different approach for hydroamination of vinylarene is realized by intermediacy of Ti -arene metal complex, facilitating nucleophilic attack of amines at the vinyl linkage due to the electron-withdrawing effect of metal. This type of activation might be brought by the use of d metals, such as Cr°, Fe , and Ru which are relatively easy to form T] -arene complexes [51]. 

Catalysts for tfie additions of amines to vinylarenes have also been developed. These catalytic reactions include some of the first hydroaminations of unstrained olefins catalyzed by late transition metals, as well as examples catalyzed by lanthanide complexes. These additions occur with Markovrukov selectivity with one set of catalysts and with anti-Markovnikov selectivity with several others. These additions occur by several different mechanisms that are presented in Section 16.5.3.2. 

Hydroaminations of 1,3-dienes and of vinylarenes occur by a different mode of nucleophilic attack. In this case, the attack occurs on a formally anionic ir-allyl or ir-benzyl... 

In addition to ri -coordinated alkenes or alkynes, the rj -coordinated allyl metals undergo hydroamination. t -AIIyI metal species of palladium and nickel are considered to be generated as major species during hydroamination of allenes, dienes, and trienes. Alkynes are also possible to produce rj -allyl species via isomerization process. In the reaction of vinylarenes, t -benzyl metal species is generated as an intermediate. 

The scope of hydroamination can be subdivided into the types of compounds containing N-H bonds that add to olefin or alkyne, or it can be divided into types of reagents containing carbon-carbon ir-bonds, such as alkenes, vinylarenes, dienes, allenes, and alkynes. Because the limitations of the catalysts and the rates of the reactions largely depend on the type of carbon-carbon Ti-bond involved in the reaction, this section of this chapter is divided into the reactions of alkenes, vinylarenes, allenes, dienes, and alkynes. 

Munro-Leighton C, Delp SA, Alsop NM, Blue ED, Gunnoe TB. A ti-Markovnikov hydroamination and hydrothiolation of electron-deficient vinylarenes catalyzed by well-defined monomeric copper(I) amido and thiolate complexes. Chem. Commun. 2008 111-113. 

Nettekoven U, Hartwig JF (2002) A new pathway for hydroamination. mechanism of palladium-catalyzed addition of anilines to vinylarenes. J Am Chem Soc 124 1166-1167... 

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