Organolanthanide-catalyzed Hydroamination Reactions

Organo-/-element-catalyzed hydroaminations have been extensively investigated for more than 10 years.1034-1038 Lanthanide metallocenes catalyze the regiospecific intermolecular addition of primary amines to acetylenic, olefinic, and diene substrates at rates which are —1/1000 those of the most rapid intramolecular analogs. Kinetic and mechanistic data argue for turnover-limiting C=C/C=C insertion into an Ln-N bond, followed by protonolysis of 

Homoleptic lanthanide alkyls of the form Ln[GH(SiMe3)2]3 (Ln = Y, La, Nd, Sm, Lu) serve as efficient precatalysts for intramolecular homogeneous hydrophosphination. Both phosphinoalkenes and phosphinoalkynes undergo cyclization to the corresponding heterocyclic structures.1055 The catalytic intramolecular hydrophosphination/cycli-zation of phosphinoalkenes and phosphinoalkynes using organolanthanide precatalysts of the type 

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As discussed in the previous sections, hydrosilylation and hydroamination reactions can be catalyzed by essentially the same catalysts under very similar reaction conditions due to the similarity in their reaction mechanisms. Hence, both reactions can be performed in one synthetic procedure as a one-pot sequence. Although less explored than hydrosilylation of C-C multiple bonds, organolanthanide-catalyzed hydrosilylation of imines is a facile straightforward process [172,173]. Imines, in particular cyclic imines, are readily available via organolanthanide-catalyzed hydroamination of alkynes. Roesky and coworkers have demonstrated that A-silylated saturated heterocycles can be smoothly obtained (38) and (39) utilizing the bis(phosphinoamide)methanide complex 12 (Fig. 8) [57,58]. The higher reactivity of aminoalkynes in the hydroamination process makes this method a valuable alternative to aminoalkene hydroamination. 

The organolanthanide-catalyzed hydroamination of the aminoalkynes 276 gives the nitrogen-containing heterocycles 277 or 278 (in the case of R = H).158 The reaction of primary amines produces the cyclic imines 278, while the reaction of secondary amines gives the cyclic enamines 277 (Scheme 89). The organolan-... 

The most thoroughly investigated group of organolanthanide-catalyzed reactions are monoolefin transformations. These include the following processes a) hydrogenation, b) oligomerization, c) polymerization, d) hydroamination, e) hydrosilylation, and f) hydroboration, which will be discussed in the above order. 

Organolanthanides catalyze the hydroamination of alkenes and alkynes, via the reaction sequence... 

Organolanthanide-catalyzed intermolecular hydrophosphination is a more facile process than intermolecular hydroamination. The reaction of alkynes, dienes, and activated alkenes with diphenylphosphine was achieved utilizing the ytterbium imine complex 9 (Fig. 8) as catalyst [185-188]. Unsymmetric internal alkynes react regioselectively, presumably due to an aryl-directing effect (48) [186]. 

Although efficient for the intramolecular hydroamination/cyclization (abbreviated IH below) of aminoalkenes (see below), organolanthanides exhibit a much lower catalytic activity for the intermolecular hydroamination of aUcenes, as exemplified by the reaction of n-PrNH2 with 1-pentene catalyzed by a neodymium complex (Eq. 4.17) [127]. 

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