Enantioselectivity in cyclopropanation catalyzed by Cu(I) complexes increased by π stacking of two monodentate oxazoline ligands

One-step templated synthesis of chiral organometallic salicyloxazoline complexes

“…Chiral oxazolinyl organometallic complexes are very important catalysts in organic chemistry [1–9]. Several organometallic complexes containing 2-(2′-hydroxyphenyl)oxazolines are reported in the literature [10–28]. These complexes exhibit good catalytic effects in asymmetric Baeyer–Villiger reactions [16–18], cyclopropanations [27, 28], and reductions of perchlorate with sulfides under mild conditions [29].…”

“…Several organometallic complexes containing 2-(2′-hydroxyphenyl)oxazolines are reported in the literature [10–28]. These complexes exhibit good catalytic effects in asymmetric Baeyer–Villiger reactions [16–18], cyclopropanations [27, 28], and reductions of perchlorate with sulfides under mild conditions [29]. The general approach to the synthesis of metal complexes begins with ligand synthesis, followed by ligand reaction with metal salts to afford organometallic complexes [30].…”

One-Pot Synthesis of Chiral Organometallic Complexes

“…Chiral oxazolinyl organometallic complexes are very important catalysts in organic chemistry [14][15][16][17][18][19][20][21][22]. Several organometallic complexes containing 2-(2′-hydroxyphenyl) oxazolines are reported in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The general approach to the synthesis of metal complexes begins with ligand synthesis, followed by ligand reaction with metal salts to afford organometallic complexes [43].…”

Use of N,N-Coordinating Ligands in Catalytic Asymmetric C--C Bond Formations: Example of Cyclopropanation, Diels--Alder Reaction, Nucleophilic Allylic Substitution

“…More stable Cu(OTf) 2 has also often been used as the copper source, but the resulting Cu(II)-ligand complex has to be reduced (often by phenylhydrazine, DIBAL, or a slight excess of the diazo reagent itself) to provide an active species. Few articles deal with results obtained by using monodentate oxazoline ligands [6,7], which are always less selective than their bidentate counterparts. Zhou et al [8,9] have prepared chiral quinolinyl-or pyridinyloxazoline ligands of type 1 and 2 (Scheme 2).…”

“…Evans group found that the nature of the counterion involved in the catalytic cycle is of major importance regarding the enantioselectivity, with SbF 6 -leading to the best results. High enantioselectivities are assumed to be obtained through a square-planar catalyst-substrate complex (56 in Scheme 27) with a counterion possessing weak coordinating properties such as SbF 6 -. A less organized one-point complex (57) may explain the lower enantioselectivity observed in the case of triflate complexes.…”