Enantioselective arylation of aldehydes catalyzed by a soluble optically active polybinaphthols ligand

A soluble chiral polymer ligand was synthesized by the polymerization of (R)-6,6′-dibutyl-3,3′-diformyl-2,2′-binaphthol (R-M-1) with 2,5-diaminopyridine (M-2) via a nucleophilic addition-elimination reaction. While arylboronic acids were used as the source of the transferable aryl group, the chiral polybinaphthols ligand in combination with Et₂Zn without Ti(OⁱPr)₄ exhibited higher enantioselectivity in asymmetric addition to aromatic aldehydes than alphatic aldehydes. When aromatic aldehydes with electron-withdrawing groups were chosen as substrates, the resulting diarylmethanols were produced in higher ee values than those with electron-donating groups as substrates. 2-Naphthaldehyde used as a substrate afforded product in 95% ee, which could be ascribed to the steric effect influence on this asymmetric arylation reaction. Moreover, the chiral polymer was easily recovered and reused, but exhibited a decrease of enantioselectivity in the third recycle.     

Synthesis and odor of optically active trans-2,2,6-trimethylcyclohexyl methyl ketones and their related compounds

The synthesis characterized by cationic olefin cyclizations accomplished using ketone enol esters and odor of novel (1R,6S)- and (1S,6R)-2,2,6-trimethylcyclohexyl methyl ketones (5) are described. The stereoselective syntheses of (E)-(1R,6S)- and (E)-(1S,6R)-1-(2,2,6-trimethylcyclohexyl)-2-buten-1-one (6) and (1R,6S)-ethyl 2,2,6-trimethylcyclohexylcarboxylate (7), useful raw materials for flavor and fragrance, starting from the (1R,6S)- and (1S,6R)-5 are also described.     

Enantioselective addition of phenylacetylene to aldehydes catalyzed by 1,3-aminophenol ligand

The 1,3-aminophenol ligand (R)-1 was found to be a good catalyst for the zinc phenylacetylene addition to aldehydes. The high activity and enantioselectivity could be improved upon by basic additives. The enantioselectivity follows a linear free energy relationship with higher enantioselectivity obtained for the more reactive aryl aldehydes.     

Highly enantioselective addition of phenylacetylene to aldehydes catalyzed by a camphorsulfonamide ligand

The asymmetric addition of phenylacetylene to aldehydes was carried out by using a camphorsulfonamide titanium complex as a catalyst. The reactions proceeded under mild conditions and gave the products with good yields and high ees. This system is very useful for the synthesis of chiral propargylic alcohol. [reaction: see text]     

Asymmetric synthesis of (−)-(S,S)-homaline

The asymmetric synthesis of (−)-(S,S)-homaline was achieved in 8 steps from commercially available starting materials using the diastereoselective conjugate addition of the novel lithium amide reagent lithium (R)-N-(3-chloropropyl)-N-(α-methyl-p-methoxybenzyl)amide to methyl cinnamate to install the correct stereochemistry. Subsequent functional group manipulation of the resultant β-amino ester and Sb(OEt)₃-mediated macrolactamisation was followed by homodimerisation to give (−)-(S,S)-homaline in 18% overall yield, representing the first asymmetric, and by far the most efficient synthesis of this natural product reported to date.     

Asymmetric addition of KCN and Ac2O to aldehydes catalyzed by recyclable polymeric salen-Ti(IV) complexes

Polymeric salen-Ti(IV) complexes were employed in the enantioselective O-acetyl cyanation of aldehydes with KCN and Ac₂O. The polymeric catalysts with appropriate crosslinking degree exhibited good activities and enantioselectivities, up to 94% yield and 91% ee were obtained at −20 °C with 1 mol % of catalyst (based on bimetallic catalytic unit). Moreover, the crosslinked polymeric catalyst could be easily recovered and reused for six consecutive runs without obvious decrease in activity and enantioselectivity.     

Asymmetric addition of methyl nitroacetate to crotonaldehyde catalyzed by chiral amines

The asymmetric Michael addition of methyl nitroacetate to crotonaldehyde catalyzed by chiral amines was carried out. The maximum chemical yield of diastereomeric products amounted to 95 %. The best asymmetric induction (42 % e.e.) was achieved in the case of catalysis by (S)-prolinol. The diastereomeric mixture was converted to a mixture of stereoisomeric 3-methyl-2-methoxycarbonylpyrrolidines. Absolute configurations of (2S,3S)-and (2R,3S)-isomers formed in excess were determined using GLC by comparison with authentic samples of racemic and optically pure forms of 3-methylproline.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1591–1595, September, 1993.     

Enantioselective addition of diethylzinc to aldehydes catalyzed by optically active 1,4-aminoalcohols

Enantioselective addition reactions of diethylzinc to aldehydes were performed by catalytic reactions with chiral 1,4-aminoalcohols. Optically active 1,4-aminoalcohols were synthesized from (+)-camphor and (−)-fenchone through four steps involving iodine-mediated lactonization of 3-hydroxy acids.     

双功能手性联萘酚配体在炔基锌对醛的不对称加成反应选择性能研究

单体2-溴吡啶, 2-溴-5-甲基吡啶, 2-氯-4-氟吡啶, 2-氯-3-三氟甲基吡啶分别与( R )-3,3′-二硼酸-2,2′-二甲氧基-1,1′-联萘 [( R )-2]在钯催化下, 通过Suzuki交叉耦合反应合成得到四个类似手性化合物( R )-3a-d。将它们应用到炔基锌对醛的不对称催化加成反应中,结果表明( R )-3a和( R )-3b的催化效果不好, 而( R )-3d只对脂肪醛有很好的催化效果,( R )-3c则对这类不对称催化反应均有很好的催化效果, 能给出高达95%的收率和99%的选择性结果。结果还表明所产生相应炔丙醇异构体构型为S,这与手性催化剂构型相反。     

Asymmetric Synthesis of （R）- and （S）-Moprolol

A simple and effective procedure for the enantioselective synthesis of （R）- and （S）-moprolol was described. The key step was the asymmetric synthesis of enantiopure （R）- and （S）-guaifenesin, which were synthesized from enantioenriched （R）-3-chloro-l,2-propanediol and （S）-epichlorohydrin via kinetics of hydrolysis resolution of racemic epichlorohydrin by chiral Salen-Co^Ⅲ complex. The e.e. values of both the optical compounds were above 98%, and the chemical structures of the target compounds were confirmed by ^1H NMR, ^13C NMR, IR, and MS.     

New optically active organoantimony (BINASb) and bismuth (BINABi) compounds comprising a 1,1′-binaphthyl core: synthesis and their use in transition metal-catalyzed asymmetric hydrosilylation of ketones

Racemic 2,2′-bis[diarylstibano]-1,1′-binaphthyls [(±)-BINASbs] and 2,2′-bis[di(p-tolyl)bismuthano]-1,1′-binaphthyl [(±)-BINABi], which are the antimony and bismuth congeners of BINAP, have been prepared from 2,2′-dibromo-1,1′-binaphthyl (DBBN) via 2,2′-dilithio-1,1′-binaphthyl intermediate by treatment with the appropriate metal halides [(p-Tol)₂SbBr, Ph₂SbBr and (p-Tol)₂BiCl]. The optical resolution of the (±)-BINASbs could be achieved via the separation of a mixture of the diastereomeric Pd-complexes derived from the reaction of (±)-BINASbs with di-μ-chlorobis{(S)-2-[1-(dimethylamino)-ethyl]phenyl-C¹,N}dipalladium(II). Optically active (R)-BINASb and (R)-BINABi could be also obtained from optically active (R)-DBBN by the same procedure. The enantiopure BINASbs have been shown to be effective chiral ligands for the rhodium-catalyzed asymmetric hydrosilylation of ketones.     

Enantioselective trifluoromethylation of aromatic aldehydes catalyzed by combinatorial catalysts

A new combinatorial catalyst system containing the disodium (R)-binaphtholate prepared in situ and a chiral quaternary ammonium salt was developed for enantioselective trifluoromethylation of aromatic aldehydes in up to 71% ee. A possible intermediate for the binaphtholate activation of the TMSCF₃ and a catalytic cycle were proposed based on the experiments.     

Chiral N,N′-dioxide-Yb(III) complexes catalyzed enantioselective hydrophosphonylation of aldehydes

Chiral N,N′-dioxide-Ytterbium(III) complexes promoted the asymmetric addition of diethyl phosphate to aldehydes, giving the corresponding products with good yields and enantioselectivities. The addition of pyridine favored both reactivity and enantioselectivity. A possible catalytic cycle was proposed to explain the mechanism of the asymmetric hydrophosphonylation of aldehydes.     

Asymmetric synthesis of 3-substituted 3,4-dihydroisocoumarins via stereoselective addition of laterally lithiated chiral 2-(o-tolyl)oxazolines to aldehydes followed by diastereomer-selective lactonization

Lateral lithiation of (S)-4-isopropyl-2-(o-tolyl)oxazoline in diethyl ether followed by the reaction with aldehydes in the presence of TMEDA produced the addition products with stereoselectivities up to 84% de. Utilization of TMEDA as a ligand is essential for the good selectivity. Rationale for the stereoselectivity is proposed based on ab initio calculation of the lateral lithio species. The major (S,S)-products lactonized faster than the minor (S,R)-products to the corresponding 3,4-dihydroisocoumarins under acidic conditions. Thus, (3S)-3,4-dihydroisocoumarins were obtained in good optical purities up to 97% ee by sequential application of these matched stereoselective reactions.     

Cyanosilylation of aldehydes catalyzed by N-heterocyclic carbenes

N-Heterocyclic carbenes produced in situ from salts of imidazolium, benzimidazolium, pyrido[1,2-c]imidazolium, imidazolinium, thiazolium, and triazolium catalyze the addition of trimethylsilylcyanide to aldehydes to yield cyanohydrin trimethylsilyl ethers. The use of C₂-symmetric imidazolidenyl carbene derived from (R,R)-1,3-bis[(1-naphthyl)ethyl]imidazolium chloride led to enantioselective cyanosilylation.     

Asymmetric addition of phenylacetylene to aldehydes catalyzed by complex of O‐sulfonyl camphor derivatives and titanium

Several novel ligands that are based on the camphor skeleton or contain the O‐sulfonyl group were synthesized and used in the asymmetric addition of phenylacetylene to aldehydes. This enantioselective reaction afforded chiral propargylic alcohols in high yields and with good to excellent levels of enantiopurity (up to 99% enantiomeric excess). Copyright © 2016 John Wiley & Sons, Ltd.     

Palladium(II)/2,2′-bipyridine-catalyzed addition of arylboronic acids to N-tosyl-arylaldimines

A Pd(II)/NO₂-bpy-catalyzed addition of the arylboronic acids to N-tosylaldimines to yield diarylmethylamines with moderate to excellent yield was developed. The use of bipyridines as the ligands is crucial in this reaction. The asymmetric version of the reaction also showed that a moderate high yield and ee value can be obtained using the pymox ligands.     

Synthesis and characterization of polybinaphthalene incorporating chiral (R) or (S)-1,1′-binaphthalene and oxadiazole units by Heck reaction

Chiral conjugated polymers P-1 and P-2 were synthesized by the polymerization of (R)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthalene ((R)-M-1) and (S)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthalene ((S)-M-1) with 2,5-bis(4-vinylphenyl)-1,3,4-oxadiazole (M-2) under Pd-catalyzed Heck coupling reaction, respectively. Both monomers and polymers were analysed by NMR, MS, FT-IR, UV, DSC-TG, fluorescent spectroscopy, GPC and CD spectra. The chiral conjugated polymers exhibit strong Cotton effect in their circular dichroism (CD) spectra indicating a high rigidity of polymer backbone. CD spectra of polymers P-1 and P-2 are almost identical and have opposite signs for their position. These polymers have strong blue fluorescence.     

Asymmetric Mukaiyama aldol reaction of silyl enol ethers with aldehydes using a polymer-supported chiral Lewis acid catalyst

Chiral N-sulfonylated α-amino acid monomer (5) derived from (S)-tryptophan was copolymerized with styrene and divinylbenzene under radical polymerization conditions to give a polymer-supported N-sulfonyl-(S)-tryptophan (6). Treatment of the polymer-supported chiral ligand with 3,5-bis(trifluoromethyl)phenyl boron dichloride afforded a polymeric Lewis acid catalyst (16) effective for asymmetric Mukaiyama aldol reaction of silyl enol ethers and aldehydes. Various aldehydes were allowed to react with silyl enol ethers in the presence of the polymeric chiral Lewis acid to give the corresponding aldol adducts in high yield with high levels of enantioselectivity.     

Asymmetric ring opening reaction of oxabenzonorbornadienes with amines promoted by iridium/NMDPP complex

As an efficient catalyst, the [Ir(COD)Cl]₂/NMDPP complex has been successfully applied to promote the asymmetric ring opening reaction of oxabenzonorbornadienes with various amines, which afforded the corresponding products in good yields (72–98%) with good enantioselectivities (80–90% ee).