Synthesis, structure, and catalytic activity of titanium(IV) and zirconium(IV) amides with chiral biphenyldiamine-based ligands

Transition‐Metal‐Catalyzed Hydroamination Reactions

“…The potential application of this impressive system in more complex organic syntheses is an exciting opportunity. Other enantioselective group 4 catalysts have been generated by the Hultzsch [73], Schafer [74,75], and Zi [76][77][78][79][80][81][82][83] groups. Over 100 new organometallic complexes have been screened, all based on axially chiral biphenyl or binaphthyl backbones and bound to the group 4 metal center through N, O, or S. Furthermore, Hultzsch [84] has disclosed Ta complexes capable of enantioselective cyclohydroamination with modest enantiomeric excess.…”

“…This focused topic has been comprehensively reviewed by Hultzsch [280] and is briefly summarized in the comprehensive review of 2008 [10]. Most published contributions have focused on the use of rare earth and early transition metal (Section 15.2.5) catalysts and indeed these have been some of the most successful examples reported to date [43,63,64,66,67,[74][75][76][77][78][79][80][81][82][83][84][85][281][282][283][284][285][286][287][288], likely because of the clear mechanistic requirement of a reactive M-N bond (single or double, depending on the mechanistic proposal) in the catalytic cycle. In late transition metals, where many reactions have been shown to proceed via outer-sphere amine addition to coordinated alkene, it is challenging to control such additions distal to the metal.…”

“…To realize expanded reactivity with unactivated alkenes, protected nitrogen substrates have been used to advantage and this will be summarized later in this section. Interestingly, while intramolecular enantioselective hydroamination of unactivated alkenes with alkylamines has been extensively reported for rare earth metals [85,[284][285][286][287] and early transition metals [43,63,64,66,67,[74][75][76][77][78][79][80][81][82][83][84]288], it was not until 2010 that late transition metals were reported to give comparable results. Buchwald [291] disclosed asymmetric intramolecular hydroamination of unprotected secondary aminoalkenes to give chiral pyrrolidine products with ee's up to 91%.…”

Synthesis, structure, and catalytic activity of chiral silver(I) and copper(II) complexes with biaryl-based nitrogen-containing ligands

“…In particular, 2,2 0 -diamino-1,1 0 -binaphthyl (BINAM) as its (R) or (S) enantiomers have been modified to give variants which bear appropriate structural and electronic features for intended specific reactions, and its derivatives have exhibited good to excellent enantioselectivities in a number of asymmetric transformations [7][8][9][10][11][12]. In recent years, we have developed a series of binaphthyldiamine-based chiral nitrogen-containing ligands, and their Ir(I), Rh(I), Ti(IV), Ag(I), Zr(IV) and lanthanide complexes are useful catalysts for a range of transformations [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Further we demonstrated that the binaphthyldiamine-based bis-ligated lanthanide amides [(S)-2-Me 2 N-C 20 H 12 -2 0 -(NCHC 4 H 3 N)] 2 LnN(SiMe 3 ) 2 with C 1 -symmetric N 3 -ligand are more effective chiral catalysts for the enantioselective hydroamination/cyclization reaction than those [(R)-C 20 H 12 (NCHC 4 H 3 N) 2 ]LnN(SiMe 3 ) 2 (thf) (Ln = Sm, Y, Yb) with C 2 -symmetric N 4 -ligands [15,17].…”

Aminopyridine stabilized group-IV metal complexes and their applications

“…13) and shorter amido-N-Hf bond than the pyridine-N-Hf bond indicating the location of negative charge on amido nitrogen atom [34]. Zr-complexes (33)(34)(35)(36)(37)(38) and Hf-complexes (43)(44)(45)(46)(47)(48) showed moderate activities for ethylene polymerization which has been presumed due to poor stability in the presence of aluminum alkyls [26,30,34]. Kempe et al hypothesized that diamine (containing an amine function at two and six position of pyridine ring)-functionalized ligands (electron rich-ligands) could enhance the stability of complex, and, hence, synthesized Hf-complexes containing electron-rich ligands through toluene elimination route [34].…”