In organic chemistry, atoms other than carbon and hydrogen are generally referred to as heteroatoms. The most common heteroatoms are nitrogen, oxygen and sulfur. Now I present to you an article called A new class of versatile chiral-bridged atropisomeric diphosphine ligands: remarkably efficient ligand syntheses and their applications in highly enantioselective hydrogenation reactions, published in 2006-05-03, which mentions a compound: 53562-86-0, mainly applied to chiral bridged diphosphine ligand preparation asym hydrogenation catalyst; iridium chiral bridged diphosphine ligand complex asym hydrogenation catalyst; ruthenium chiral bridged diphosphine ligand asym hydrogenation complex catalyst; ketoester asym hydrogenation beta hydroxy ester preparation; dehydroamino acid asym hydrogenation beta amino acid preparation; intramol Ullmann coupling bisiodoaryl diphosphine dioxide, Quality Control of (S)-Methyl 3-hydroxybutanoate.
A series of chiral diphosphine ligands denoted as PQ-Phos (I, II, and III; n = 0, 1, 2) was prepared by atropdiastereoselective Ullmann coupling and ring-closure reactions. The Ullmann coupling reaction of the biaryl diphosphine dioxides (IV; n = same as above) is featured by highly efficient central-to-axial chirality transfer with diastereomeric excess >99%. This substrate-directed diastereomeric biaryl coupling reaction is unprecedented for the preparation of chiral diphosphine dioxides, and our method precludes the tedious resolution procedures usually required for preparing enantiomerically pure diphosphine ligands. The effect of chiral recognition was also revealed in a relevant asym. ring-closure reaction of (S)- or (R)-HO-BIPHEPO (V) or (VI) with chiral alkanediol dimesylate or ditosylate (VII; R = Ms, n = 0; R = Ts, n = 1 or 2). The chiral tether bridging the two aryl units creates a conformationally rigid scaffold essential for enantiofacial differentiation; fine-tuning of the ligand scaffold (e.g., dihedral angles) can be achieved by varying the chain length of the chiral tether. The enantiomerically pure Ru- and Ir-PQ-Phos complexes have been prepared and applied to the catalytic enantioselective hydrogenations of α- and β-ketoesters (C:O bond reduction) of formula R1COCO2R2 (R1 = Me or Ph, R2 = Me; R1 = Me, iso-Pr, Ph, or PhCH2CH2) and R1COCHR2CO2R3 (R1 = Me, R2 = H, R3 = Me, Et, or CH2Ph; R1 = ClCH2 or Ph, R2 = H, R3 = Et; R1 = Ph, R2 = Cl, R3 = Et) to chiral α- or β-hydroxy esters of formula R1CH(OH)CO2R2 and R1CH(OH)CHR2CO2R3, 2-(6′-methoxy-2′-naphthyl)propenoic acid, alkyl-substituted β-dehydroamino acids (C:C bond reduction) of formula R2O2CCH:C(R1)NHAc (R1 = Me, Et, iso-Pr, or tert-Bu, R2 = me; R1 = Me or n-Pr, R2 = Et) to chiral β-amino acid esters of formula R2O2CCH2CHC(R1)NHAc, and N-heteroaromatic compounds (C:N bond reduction) (VIII; R1 = Me, R2 = Me, H, MeO; R1 = Ph, R2 = H), (IX), and (X) to chiral heterocyclic compounds (XI), (XII), and (XIII). An excellent level of enantioselection (up to 99.9% ee) has been attained for the catalytic reactions. In addition, the significant ligand dihedral angle effects on the Ir-catalyzed asym. hydrogenation of N-heteroaromatic compounds were also revealed.
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Reference:
Piperazine – Wikipedia,
Piperazines – an overview | ScienceDirect Topics