Catalytic synthesis of amines and N-containing heterocycles: Amidate complexes for selective C–N and C–C bond-forming reactions

Abstract

The direct, 100 % atom-economic, and selective synthesis of amines is a challenging task that can be achieved, making use of early transition-metal catalysts. Here we report the synthesis and application of group 4 and 5 high-oxidation-state metal amidate complexes in catalytic C-N (hydroamination) and C-C (hydroaminoalkylation) bond-forming reactions to access substituted amines.

Synthesis, structure, and reactivity of tris(amidate) mono(amido) and tetrakis(amidate) complexes of group 4 transition metals

“…application is hydroamination, as bis(amidate) supported group 4 systems for hydroamination have precedence in the literature. 4,6,8,21,24,35,36 To the best of our knowledge, tris-(amidate) complexes of early transition metals have not been reported for this catalytic transformation.…”

“…In recent years, we and others have reported the synthesis of a variety of monometallic mono and bis(N,O)-ligated group 3, 4, and 5 metal complexes with broad applications in catalysis. [1][2][3][4][5][6][7][8][9][10] These complexes include mono and bis(amidate) tantalum(V) complexes for the hydroaminoalkylation of amines, 10,11 mono and bis(amidate) yttrium(III) complexes for the hydroamination of aminoalkenes 9,12 and the amidation of aldehydes, 13 bis-(2-pyridonate) titanium(IV) complexes for the random copolymerization of ε-caprolactone and rac-lactide, 14 bis(ureate) zirconium(IV) complexes 15,16 as well as bis(amidate) zirconium(IV) and titanium(IV) complexes for hydroamination 7,12,[15][16][17][18][19][20][21][22] and olefin polymerization. 2 These complexes can be generated from the homoleptic metal amide or alkyl starting materials (M(NR 2 ) x or MR x ) via a protonolysis reaction (Scheme 1) with the organic proligand.…”

The Mechanism of the Titanium‐Catalyzed Hydroaminoalkylation of Alkenes

“…Although hydroaminoalkylation of alkenes has already been achieved with Ta,4–7 Ti,8 and Zr catalysts,6b, 9 the mechanism of the reaction remains unclear. So far only a few mechanistic suggestions have been published,4b, 5, 6, 8, 9 but no detailed mechanistic data are available in the literature.…”

Tantallaaziridines: from synthesis to catalytic applications

“…Notably, the chemistry of zirconaaziridines is particularly rich due to their extensive application in the stereoselective synthesis of N-containing small molecules, 5 and this focused topic has been comprehensively reviewed. 6 While related group 5 and 6 systems have been explored in the literature for over 20 years, most recently group 5 complexes, [7][8][9] and especially tantallaaziridine species [10][11][12][13][14] have been implicated in a 100% atom-economic C-C bond forming catalytic reaction, the direct α-alkylation of amines or hydroaminoalkylation (Scheme 1). This reaction is the formal addition of a C-H bond across an alkene and proceeds via C-H activation of the sp 3 hybridized C-H bond adjacent to nitrogen.…”