Actinides, hydroamination

Hydrido(trialkylsilyl)silyllithiums, preparation, 3, 424 Hydroacylations, olefins, 10, 142 Hydroalkoxylations and etherification, 10, 672 in etherification, 10, 683 Hydroaluminations for C-E bond formation characteristics, 10, 857 chemoselectivity, 10, 859 mechanism, 10, 858 overview, 10, 839-870 stereoselectivity, 10, 861 total synthesis applications, 10, 865 characteristics, 3, 275 process and examples, 9, 268 via Ti(IV) complexes, 4, 658 Hydroaminations actinide-catalyzed, 4, 237 in aminations... 

Intramolecular addition of amine N-H bonds to carbon-carbon multiple bonds would afford nitrogen heterocycles. To realize catalytic cyclization of a,co-aminoalkenes or aminoalkynes, various catalytic systems have been developed especially with early transition metals such as titanium, zirconium, lanthanide metals, and actinide metals [ 12], Late-transition-metal catalysis based on Ni, Pd, and Rh has also proved to be efficient [ 12], Recently, the ruthenium-catalyzed intramolecular hydroamination of aminoalkynes 15 was reported to afford 5-7-membered ring products 16 in various yields (Eq. 6) [13]. Among... 

Hydroamination of Alkynes Catalyzed by Lanthanide and Actinide Complexes... 

Some of the most active catalysts for the hydroamination of alkynes are based on lanthanides and actinides. The turnover frequencies for the additions are higher than those for lanthanide-catalyzed additions to alkenes by one or two orders of magnitude. Thus, intermolecular addition occurs with acceptable rates. Examples of both intermolecular and intramolecular reactions have been reported (Equations 16.87 and 16.88). Tandem processes initiated by hydroamination have also been reported. As shown in Equation 16.89, intramolecular hydroamination of an alk5me, followed by cyclization with the remaining olefin, generates a pyrrolizidine skeleton. Hydroaminations of aminoalkynes have also been conducted with the metallocenes of the actinides uranium and thorium. - These hydroaminations catalyzed by lanthanide and actinide complexes occur by insertion of the alkyne into a metal-amido intermediate. 

As discussed in Chapter 9, the insertion of olefins and alk)nes into metal-amido complexes is limited to a few examples. Such insertion reactions are proposed to occur as part of the mechanism of the hydroamination of norbomene catalyzed by an iridium(I) complex and as part of the hydroamination of alkenes and alkynes catalyzed by lanthanide and actinide metal complexes. This reaction was clearly shown to occur with the iridium(I) amido complex formed by oxidative addition of aniline, and this insertion process is presented in Chapter 9. The mechanism of the most active Ir(I) catalyst system for this process involving added fluoride is imknown. 

The hydroamination of olefins has been shown to occur by the sequence of oxidative addition, migratory insertion, and reductive elimination in only one case. Because amines are nucleophilic, pathways are available for the additions of amines to olefins and alkynes that are unavailable for the additions of HCN, silanes, and boranes. For example, hydroaminations catalyzed by late transition metals are thought to occur in many cases by nucleophilic attack on coordinated alkenes and alkynes or by nucleophilic attack on ir-allyl, iT-benzyl, or TT-arene complexes. Hydroaminations catalyzed by lanthanide and actinide complexes occur by insertion of an olefin into a metal-amide bond. Finally, hydroamination catalyzed by dP group 4 metals have been shown to occur through imido complexes. In this case, a [2+2] cycloaddition forms the C-N bond, and protonolysis of the resulting metallacycle releases the organic product. 

Reznichenko A, Hultzsch K (2012) Early transition metal (group 3-5, lanthanides and actinides) and main group metal (group 1, 2, and 13) catalyzed hydroamination. Top Organomet Chem. doi 10.1007/3418 2011 22... 

Early Transition Metal (Group 3-5, Lanthanides and Actinides) and Main Group Metal (Group 1, 2, and 13) Catalyzed Hydroamination... 

Only a limited number of organoactinide catalysts have been investigated for the hydroamination/cyclization of aminoalkenes (Fig. 4, Table 2) [55, 96-98]. The constrained geometry catalysts 11-An (An = Th, U) show high activity comparable to the corresponding rare earth metal complexes and can be applied for a broad range of substrates [55, 96, 97]. The ferrocene-diamido uranium complex 12 was also catalytically active for aminoalkene cyclization, but at a somewhat reduced rate [98]. Mechanistic studies suggest that the actinide-catalyzed reaction occurs via a lanthanide-like metal-amido insertion mechanism and not via an imido mechanism (as proposed for alkyne hydroaminations), because also secondary aminoalkenes can be cyclized [55, 98]. 

A number of actinide complexes have been investigated with respect to their catalytic activity in the intermolecular hydroamination of terminal alkynes with primary ahphatic and aromatic amines [98, 206-209]. Secondary amines generally do not react and the reaction is believed to proceed via an metal-imido species similar to that of group 4 metal complexes. The reaction of Cp 2UMc2 with sterically less-demanding aliphatic amines leads exclusively to the anti-Markovnikov adduct in form of the -imine (31) [207] however, sterically more demanding amines, e.g., t-BuNH2, result in exclusive alkyne dimerization. The ferrocene-diamido uranium complex 12 (Fig. 4) catalyzes the addition of aromatic amines very efficiently (32) [98]. 

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