Asymmetric allylboration of acyl imines catalyzed by chiral diols

Chiral BINOL-derived diols catalyze the enantioselective asymmetric allylboration of acyl imines. The reaction requires 15 mol % (S)-3,3'-Ph2-BINOL as the catalyst and allyldiisopropoxyborane as the nucleophile. The reaction products are obtained in good yields (75-94%) and high enantiomeric ratios (95:5-99.5:0.5) for aromatic and aliphatic imines. High diastereoselectivities (diastereomeric ratio > 98:2) and enantioselectivities (enantiomeric ratio > 98:2) are obtained in the reactions of acyl imines with crotyldiisopropoxyboranes. This asymmetric transformation is directly applied to the synthesis of Maraviroc, the selective CCR5 antagonist with potent activity against HIV-1 infection. Mechanistic investigations of the allylboration reaction including IR, NMR, and mass spectrometry studies indicate that acyclic boronates are activated by chiral diols via exchange of one of the boronate alkoxy groups with activation of the acyl imine via hydrogen bonding.     

Asymmetric propargylation of ketones using allenylboronates catalyzed by chiral biphenols

Chiral biphenols catalyze the enantioselective asymmetric propargylation of ketones using allenylboronates. The reaction uses 10 mol % of 3,3'-Br(2)-BINOL as the catalyst and allenyldioxoborolane as the nucleophile, in the absence of solvent, and under microwave irradiation to afford the homopropargylic alcohol. The reaction products are obtained in good yields (60-98%) and high enantiomeric ratios (3:1-99:1). Diastereoselective propargylations using chiral racemic allenylboronates result in good diastereoselectivities (dr >86:14) and enantioselectivities (er >92:8) under the catalytic conditions.     

Asymmetric transfer hydrogenation of ketones catalyzed by chiral phosphineiridium complexes

The complexes formed in situ from Ir(COD)acac and chiral menthylphenylphosphines proved to be active catalysts in the hydrogen transfer reaction from isopropanol to prochiral ketones. When acetophenone was used, optical yields of up to 42% were achieved, the configuration of the carbinols being dependent on the bulkiness of the phosphine employed. Concerning the reaction rate, the activation process and the P/Ir ratio, the two menthyl-substituted phenylphosphines display different behaviour.     

Asymmetric reduction of ketones with sodium aluminum hydride modified by various chiral diols

New stereoselective reducing reagents were preparedin situ by modification of NaAlH₄ with various chiral diols. The efficiency of 1,4- and 1,3-diols as chiral auxiliaries in the reactions of alkyl aryl ketones with modified NaAlH₄ was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation does not necessarily participate at the stage governing the reaction stereochemistry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp 459–464, March, 2000.     

Asymmetric hydroazidation of α-substituted vinyl ketones catalyzed by chiral primary amine

We report herein the first example of asymmetric hydroazidation of α-substituted vinyl ketones by using chiral primary amines as the catalysts.A simple chiral primary-tertiary diamine catalyst derived from lphenylalanine was found to readily promote this aza-Michael addition reaction with enamine protonation as the key stereogenic step,thus enabling the effective synthesis of α-chiral β-azido ketones with good yields and moderate enantioselectivities.     

Asymmetric synthesis of Wieland-Miescher and Hajos-Parrish ketones catalyzed by an amino-acid-derived chiral primary amine

This paper describes a simple chiral primary amine-catalyzed highly efficient and practical protocol for the synthesis of both Wieland-Miescher ketone and Hajos-Parrish ketone as well as their analogues. The reaction can be conducted in gram scale with 1% mol catalyst loading producing high enantioselectivity (up to 96% ee) and excellent yields (up to 98%). This procedure represents one of the most efficient methods for the synthesis of these versatile chiral building blocks.     

Asymmetric allylboration of aldehydes and ketones using 3,3'-disubstitutedbinaphthol-modified boronates

Allylboronates derived from 3,3'-disubstituted 2,2'-binaphthols react with aldehydes and ketones to give the expected allylated products with up to >99:1 er. Highest selectivities were observed for aromatic ketones. The bis(trifluoromethyl) derivative is particularly outstanding in terms of reactivity, selectivity, and robustness. [reaction: see text]     

Asymmetric transfer hydrogenation of ketones catalyzed by rhodium and iridium complexes with chiral bidentate Schiff's bases

Rhodium and iridium complexes of Schiff's bases derived from (1R,2R)- and (1S,2S)-diaminocyclohexane catalyze asymmetric transfer hydrogenation of alkyl aryl ketones in PrⁱOH at room temperature to give chiral secondary alcohols (up to 65% ee).     

手性环状二胺催化的不对称Diels-Alder反应

研究了一种结构新颖、合成路线简单的手性二胺催化的Diels-Alder反应,考察了各种Br nsted酸助催化剂、温度、溶剂和手性二胺分子中不同的取代基对反应的影响.研究结果表明:该类催化剂在催化Diels-Alder反应中表现出较高的催化活性和中等的立体选择性.     

Asymmetric Diels-Alder reaction catalyzed by chiral bases

Anthrone has been found to react with N-methyl maleimide in the presence of catalytic amounts of various chiral β-amino alcohols. The optically active cycloadduct 3a has been obtained in excellent yield. Several features of the reaction have been studied.     

手性钛配合物催化不对称反应研究

手性钛配合物是一类很有用的手性催化剂,在许多反应中显示出了良好的催化活性和高的对映选择性。在我们研究的系列反应中,发现手性钛配合物是一类优良的手性催化剂,其中不对称催化杂Diels-Alder反应制备二氢吡喃酮(99%ee),不对称催化硫醚氧化成亚砜反应(96%ee)和不对称催化硅腈化反应(87%ee),都获得了好的催化活性和高的对映选择性。我们对以上反应中其催化剂的用量、溶剂、催化剂浓度和抗衡离子的Lewis酸碱性、底物的结构与对映选择性的关系、催化循环机理等进行了较系统、深入的研究,发现非共价相互作用和分子识别现象在不对称催化反应中显示出重要的作用,为进一步设计新的手性催化剂,发展不对称催化反应提供了基础数据。     

Asymmetric petasis reactions catalyzed by chiral biphenols

Chiral biphenols catalyze the enantioselective Petasis reaction of alkenyl boronates, secondary amines, and ethyl glyoxylate. The reaction requires the use of 15 mol % of (S)-VAPOL as the catalyst, alkenyl boronates as nucleophiles, ethyl glyoxylate as the aldehyde component, and 3 A molecular sieves as an additive. The chiral alpha-amino ester products are obtained in good yields (71-92%) and high enantiomeric ratios (89:11-98:2). Mechanistic investigations indicate single ligand exchange of acyclic boronate with VAPOL and tetracoordinate boronate intermediates.     

Asymmetric transfer hydrogenation of ketones catalyzed by ruthenium(II) complexes bearing a chiral phosphinoferrocenyloxazoline ligand

The catalytic activity in asymmetric transfer hydrogenation of ketones using octahedral and half-sandwich (η⁵-indenyl and η⁶-arene) ruthenium(II) complexes containing the chiral ligand (4S)-2-[(S_p)-2-(diphenylphosphino)ferrocenyl]-4-(isopropyl)oxazoline (FcPN) has been explored. Catalytic studies with complex fac-[RuCl₂{η²(P,N)-FcPN}(PMe₃)₂] (1) show excellent TOF values (9600 h⁻¹). Experiments in the presence of free FcPN, which lead to an increase in conversion rates and ee values when the catalyst is complex [Ru(η⁵-C₉H₇){κ²(P,N)-FcPN}(PPh₃)][PF₆] (4) have been carried out. The characterization of the new complexes mer-trans-[RuCl₂{P(OMe)₃}₂{κ²(P,N)-FcPN}] and of the water-soluble complexes fac- and mer-trans-[RuCl₂(PTA)₂{κ²(P,N)-FcPN}] is also reported.     

Asymmetric 1,4-addition of alkenylzirconium reagents to α,β-unsaturated ketones catalyzed by chiral rhodium complexes

Highly enantioselective 1,4-addition of alkenylzirconocene chlorides to α,β-enones was found to be catalyzed by a chiral rhodium complex generated from [Rh(cod)(MeCN)₂]BF₄ and (S)-BINAP. The reaction can be applied to either cyclic or acyclic enones and the optical yield was up to 99% ee. The reaction mechanism would involve the transmetalation between the alkenylzirconocene chloride and the rhodium complex to give the alkenylrhodium species as a key intermediate.     

Asymmetric henry reaction catalyzed by chiral schiff base

Four chiral Schiff bases were synthesized conveniently from chiral amino alcohol and 2-hydroxynaphthalene-1-carbaldehyde. These ligands were used to catalyze the addition of nitroalkanes to aldehydes under ambient conditions in good yields with up to 91% ee.     

Asymmetric allyltributylstannane addition to ketones catalyzed by chiral PYBOX-In(III) complex immobilized in ionic liquid

An indium complex of chiral PYBOX was applied in the catalytic asymmetric allylation of ketones in the ionic liquid. It was found that this chiral indium complex was strong enough to promote the reaction of ketones with allyltributylstannane smoothly. The products were obtained in moderate to high enantioselectivities, and the chiral catalyst immobilized in the ionic liquid could be reused with comparable enantioselectivities and yields.     

Asymmetric ene reaction catalyzed by chiral organoaluminum reagent

The asymmetric ene reaction of prochiral aldehydes with alkenes has been effected by chiral organoaluminum reagent providing optically active homoallylic alcohols in both enantiomeric forms with high enantiomeric purity.