Chiral tetrahedral complex catalyzing asymmetric addition of diethylzinc to benzaldehyde

The optical active alkyne-bridged Mo-Co heterometal complexes are synthesized by the chiral phase transfer catalyst (N-benzylcinchorin chloride) induced metal exchange reaction. The complex is used as catalyst to promote the asymmetric addition of diethylzinc to benzaldehyde. The ee value of the product alcohol is 5.7%, which illustrates the asymmetric induction of the tet-rahedral framework chirality in asymmetric catalysis reaction for the first time.     

N-heterocyclic carbene ligands in copper-catalyzed addition of diethylzinc to N-sulfonylimines

N-Heterocyclic carbenes (NHCs) were generated in-situ from imidazolium and imidazolinium salts by deprotonation of C-2 hydrogen and were used as ligands in the copper-catalyzed addition of diethylzinc to N-sulfonylimines. The copper-NHC complexes were shown to possess an efficient ligand acceleration effect (LAE).     

Rh(I)-catalyzed asymmetric addition of arylboronic acids to NH isatins

The transition metal-catalyzed asymmetric variant of the title reaction is normally limited to N-protected isatins. However, Rh(I)/chiral sulfoxide phosphine complexes were found to catalyze the enantioselective addition of arylboronic acids to NH isatins under mild conditions. A variety of chiral 3-aryl-3-hydroxyl-2-oxindoles were obtained with high yields and with good to excellent enantioselectivities (85–92% ee).     

Chiral quinolinyl-oxazolines as ligands for copper(I)-catalyzed asymmetric cyclopropanation

Chiral quinolinyl-oxazoline compounds have been synthesized from enantiomerically pure amino alcohols and 8-quinoline-carboxylic acid using a convenient procedure. Asymmetric cyclopropanation of styrene with diazoacetates in the presence of 1 mol% of CuOTf and quinolinyl-oxazolines gave 2-phenylcyclopropane carboxylates in moderate enantiomeric excesses.     

Pd(II)-catalyzed asymmetric addition of malonates to dihydroisoquinolines

We have developed a highly efficient reaction for catalytic asymmetric addition of malonates to dihydroisoquinolines using chiral Pd(II) complexes. In the reactions, substrates with various substitution patterns were available, and the reactions were complete within several hours (<3 h in most cases) under mild reaction conditions, affording various optically active C1-substituted tetrahydroisoquinoline derivatives (up to 98% yield, up to 97% ee). Furthermore, slow addition of DDQ allowed the in situ generation of the reactive intermediate from the corresponding N-Boc-protected amine, and dehydrogenative addition reaction was successfully demonstrated.     

Chiral (acyclic diaminocarbene)gold(I)-catalyzed dynamic kinetic asymmetric transformation of propargyl esters

A highly enantioselective transformation catalyzed by chiral (acyclic diaminocarbene)gold(I) complexes is reported. The enantioselective synthesis of 2-substituted chromenyl pivalates from racemic phenol-substituted propargyl pivalates was developed. Rearrangement of the substrates in the presence of cationic gold gave allene intermediates, whose cyclization resulted in formation of enantioenriched product through a dynamic kinetic asymmetric transformation.     

Chiral sulfur-containing ligands for iridium(I)-catalyzed asymmetric transfer hydrogenation of aromatic ketones

New efficient catalyst systems, coupled with IrCl(COD)PPh₃ and chiral [SNNS]-type ligands, were employed in the asymmetric transfer hydrogenation of aromatic ketones under mild reaction conditions. The corresponding optically active alcohols were obtained in high yield and good to excellent enantioselectivities (up to 96% ee). The chiral Ir(I) complexes with the ligands of [SNNS]-type were also prepared and characterized, which showed good enantioselectivity and high activity. The reactions can be performed in air and the catalytic experiments are greatly simplified.     

Chiral bis(amino alcohol)oxalamides as ligands for asymmetric catalysis. Ti(IV) catalyzed enantioselective addition of diethylzinc to aldehydes

Several chiral bis(aminoalcohol)oxalamides with C₂-symmetry have been prepared and used as ligands for the enantioselective addition of diethylzinc to aromatic and aliphatic aldehydes. The reaction proceeds in the presence of titanium isopropoxide to give the corresponding (S)-alcohols with ee up to 78%. In the absence of Ti(IV), the alcohols with the opposite configuration are obtained.     

Synthesis of new chiral 1,2,3,4-tertrahydroisoquinoline β-amino alcohol for asymmetric diethylzinc addition to aryl aldehydes (I)

Four new chiral 1,2,3,4-tetrahydroisoquinoline-derived β-amino alcohols were synthesized from commercially available L-DOPA.These ligands were evaluated in the asymmetric addition of diethylzinc to benzaldehydes and showed different catalytic activities (up to 86% ee).The solvent played an important role in the enantioselective process.The transition state models were proposed to explain the reversion of the product configuration.     

FeCl3催化Et2Zn与芳香醛的加成反应研究

以FeCl_3作为催化剂, 研究了Et_2Zn与芳香醛的加成反应, 考察了催化剂、溶剂、催化剂与Et_2Zn用量及温度对该反应的影响. 实验结果表明: 在60℃, 1.2当量Et_2Zn, 甲基环戊基醚为溶剂的反应条件下, 10 mol% FeCl_3可以较高效的将各种芳香醛转化为仲醇.     

Rh(I)-catalyzed addition of alkenylzirconocene chlorides to aldimine derivatives

[RhCl(COD)]₂ (2 mol%) catalyzed reactions of alkenylzirconocene chloride complexes to N-Ts, -PO(OEt)₂ and COOR aldimine derivatives were efficiently carried out in dioxane at room temperature to give allylic amine derivatives in excellent yields. This is the first example of the catalytic addition reactions of alkenylzirconocene chloride complexes to aldimine derivatives.     

Gold(I)-catalyzed asymmetric cyclopropenation of internal alkynes

Highly enantioselective cyclopropenation of internal alkynes with aryldiazoacetates was achieved using the binuclear gold catalyst (S)-xylylBINAP(AuCl)(2), activated by silver hexafluoroantimonate.     

Cu(I)-catalyzed asymmetric diamination of conjugated dienes

A Cu(I)-catalyzed asymmetric diamination for a variety of conjugated dienes and a triene with encouraging ee's has been effectively achieved using (R)-DTBM-SEGPHOS as a chiral ligand and di- tert-butyldiaziridinone as the nitrogen source.     

Dramatic catalyst evolution in the asymmetric addition of diethylzinc to benzaldehyde

We have observed product ee's that begin at 20% at low reaction conversion and rise to 79% ee at the completion of the reaction in the asymmetric addition of alkyl groups to benzaldehyde. This rare behavior is attributed to autoinduction, in which the catalyst evolves by incorporation of the product. Based on this, we have been able to optimize the catalyst by variation of achiral, rather than enantiopure ligands.     

Phosphonite ligands for enantioselective copper(I)-catalysed conjugate addition of diethylzinc to enones

A wide variety of novel chiral monodentate phosphonite ligands derived from binaphthol and biphenanthrol have been tested as ligands in the copper(I)-catalysed conjugate addition of diethylzinc to enones, resulting in e.e.s of up to 82% for chalcone.     

Novel polymer-supported chiral catalysts for the asymmetric addition of diethylzinc to aldehydes

Newly synthesized polymer-supported chiral amino alcohol catalysts 5a and 5b have been proved to be effective for the enantioselective addition of diethylzinc to aldehydes, affording the corresponding sec-alcohols in moderate enantiomeric excesses with good to excellent yields. The recycled catalyst could be reused in the same reaction without significant deterioration in performance.     

Chiral N-heterocyclic carbene--Pd(0)-catalyzed asymmetric diamination of conjugated dienes and triene

Studies show that a variety of conjugated dienes and triene can be enantioselectively diaminated using di-tert-butyldiaziridinone as nitrogen source and chiral N-heterocyclic carbene-Pd(0) complex as catalyst in good enantioselectivity (62-91% ee) with high regio- and diastereoselectivity.