Synthesis and characterization of a new C2-symmetrical chiral tridentate N-heterocyclic carbene ligand coordinated Cr(III) complex

The preparation of a new C2-symmetrical chiral tridentate N-heterocyclic carbene (NHC) ligand coordinated Cr(III) complex is described. The new NHC ligand was prepared as its AgBr complex, which was stable but smoothly underwent carbene exchange reaction with CrCl2 to afford the new NHC ligand coordinated Cr(III) complex. The X-ray crystallographic analysis of the Cr(III) complex revealed its distorted octahedral form. The Cr(III) complex mediated reaction of allylbromide with benzaldehyde did not afford products under the catalytic conditions reported by us.

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(S)-(4-Isopropyl-4,5-dihydrooxazol-2-yl)methyl methanesulfonateC8H15NO4S>99% ee[α]D22 = −32 (c 0.52, CHCl3)Source of chirality: amino acidAbsolute configuration: (S)

(S)-2-Bromomethyl-4-isopropyl-4,5-dihydrooxazoleC7H12BrNO>99% ee[α]D21 = −44 (c 1.4, CHCl3)Source of chirality: amino acidAbsolute configuration: (S)

(S)-2-((1H-Benzo[d]imidazol-1-yl)methyl)-4-isopropyl-4,5-dihydrooxazoleC14H17N3O>99% ee[α]D21 = −29 (c 3.5, CHCl3)Source of chirality: amino acidAbsolute configuration: (S)

(S)-1,3-Bis(2-((1-hydroxy-3-methylbutan-2-yl)amino)-2-oxoethyl)-1H-benzo[d]imidazol-3-ium bromideC21H33BrN4O4>99% ee[α]D23 = −7.9 (c 0.19, MeOH)Source of chirality: amino acidAbsolute configuration: (S)

(S)-1,3-Bis(2-((1-bromo-3-methylbutan-2-yl)amino)-2-oxoethyl)-1H-benzo[d]imidazol-3-ium bromideC21H31Br3N4O2>99% ee[α]D23 = −29 (c 0.14, CHCl3)Source of chirality: amino acidAbsolute configuration: (S)

(S)-(1,3-Bis((4-isopropyl-4,5-dihydrooxazol-2-yl)methyl)-1,3-dihydro-2H-benzo[d]imidazol-2-ylidene)silver(III) bromideC21H28AgBrN4O2>99% ee[α]D23 = −2.2 (c 0.23, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S)

(S)-(1,3-Bis((4-isopropyl-4,5-dihydrooxazol-2-yl)methyl)-1,3-dihydro-2H-benzo[d]imidazol-2-ylidene)chromium(III) bromide dichlorideC21H28BrCl2C5N4O2>99% ee[α]D23 = −16 (c 0.11, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S)