Palladium catalysis hydroamination

In 2003, O Shaughnessy and Scott reported the first example of rare-earth metal complexes supported by biaryl diamide ligands as the catalysts for the hydroamination reactions [159]. A series of C2 symmetric secondary diamine proligands L37-L40 were prepared by arylations of (7 )-2,2 -diamino-6,6 -dimethybiphenyl under palladium catalysis. L37 reacted with complexes [Ln N(SiHMe2)2 3(THF)2] to form the biaryl diamide complexes [Ln(L37) N(SiHMe2)2 (THF)2] (Ln = Y (190), La (191), Sm (192)). Deprotonation... 

Other examples of microwave-assisted catalysis include allylic alkylation, both palladium catalyzed and molybdenum catalyzed. In the latter case, air stable precursor complexes could be used under non-inert conditions. Microwave-enhanced Pauson-Khand reactions have also been reported, as have hydroamination of alkynes, and metathesis of functionalized alkynes. " Recently, microwave enhancement has been applied to C-H activation reactions, for example, for the formation of functionalized heterocycles, allowing the reaction to be performed with no solvent purification and minimal precautions to exclude air. A solvent-free chelation-assisted hydroacylation... 

Larock developed a powerful approach to isoquinolines which involves copper-catalyzed hydroamination of A -ferf-butyl-2-(l-alkynyl)benzaldimine accompanied by elimination of ferf-butyl group (Eq. 4) [55-59]. Asao and Yamamoto reported a novel synthesis of 1,2,3-trisubstituted isoquinolines through attack of a carbon nucleophile to the carbon-nitrogen double bond of iV-alkyl-2-(l-alky-nyl)benzaldimine and simultaneous hydroamination catalyzed by transition metal [60]. They also achieved isoquinoline synthesis by transition metal-free three-component coupling (Eq. 5) [61]. Takemoto and Yanada reported a related isoquinoline formation by a catalysis of carbophilic Lewis acids such as indium(III), Ni(II), or Au(I)/Ag(I) [62, 63]. Oikawa succeeded in palladium-catalyzed three-component... 

Amine activatitMi pathway has been well studied in catalysis by lanthanides, early transition metals, and alkali metals. In metal amide chemistry of late transition metals, there are mainly two pathways to synthesize metal amide complexes applicable under hydroamination conditions [54], One is oxidative addition of amines to produce a metal amide species bearing hydride (Scheme 8a). The other gives a metal amide species by deprotonation of an amine metal intermediate derived from the coordination of amines to metal center, and it often occurs as ammonium salt elimination by the second amine molecule (Scheme 8b). Although the latter type of amido metal species is rather limited in hydroamination by late transition metals, it is often proposed in the mechanism of palladium-catalyzed oxidative amination reaction, which terminates the catalytic cycle by p-hydride elimination [26]. Hydroamination through aminometallation with metal amide species demands at least two coordination sites on metal, one for amine coordination and another for C-C multiple bond coordination. Accordingly, there is a marked difference between the hydroamination via C-C multiple bond activation, which demands one coordination site on metal, and via amine activation. 

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