Highly Enantioselective Intramolecular Morita‐Baylis‐Hillman Reaction Catalyzed by Mannose‐Based Thiourea‐phosphine

The saccharide‐based chiral bifunctional thiourea‐phosphines were developed as chiral organocatalysts for the intramolecular Morita‐Baylis‐Hillman reaction of ω‐formyl‐enones. With only 2 mol% of thiourea‐phosphine catalyst 3c , chiral functionalized cyclohexenes were achieved under mild reaction conditions with excellent yields and enantioselectivities.     

Amination of the Baylis–Hillman Acetates in Ethanol

Baylis–Hillman acetates in EtOH were substituted by various nitrogen nucleophiles to give the corresponding trisubstituted alkenes in high yields.     

α‐ZrP/Uracil/Cu2+ nanoparticles as an efficient catalyst in the Morita‐Baylis‐Hillman reaction

A facile synthesis of uracil‐Cu²⁺ nanoparticles immobilized on alpha‐zirconium hydrogen phosphate (α‐ZrP), abbreviated as α‐ZrP/Uracil/Cu²⁺, was presented. This compound was synthesized by the thermal method and used as a reusable catalyst for the Morita‐Baylis‐Hillman reaction without any additives. First, (3‐ iodopropyl) trimethoxysilane as a linker is reacted with α‐ZrP support to give the α‐ZrP/IPTMOS. Addition of uracil and then the addition of copper (II) acetate to α‐ZrP/IPTMOS results in the production of selected catalyst. The Morita‐Baylis‐Hillman reaction catalyzed by α‐ZrP/Uracil/Cu^{2 +} demonstrated high product yield, short reaction time and a straightforward work‐up. The catalyst with enough outside surface was easily recovered using centrifugation and reused five times without a significant reduction in its activity.     

Accelerated Amination of Baylis–Hillman Acetates Under Ultrasound Irradiation

The amination of the Baylis–Hillman acetates with primary amines can be dramatically promoted with improved yields and shortened reaction time under ultrasound irradiation. The selected aromatic, heteroaromatic, and aliphatic amines were investigated as the effective candidates for the sonochemical transformation.     

Enatioselective Chalcogeno‐Baylis‐Hillman Reaction of Arylaldehydes with MVK and Acrylates Catalyzed by Chiral Thiepin‐TiCl4 Complex

In a rational chiral molecular design of chalcogenides, optically active thiepin with C₂‐symmetric chirality was synthesized from commercially available thiophene. Then enatioselective Chalcogeno‐Baylis‐Hillman reactions of arylaldehydes with methyl vinyl ketone (MVK) and acrylates were investigated in the presence of thiepin‐Lewis acid complex. Finally, up to 64% ee was achieved in the presence of 0.2 equiv. of (S)‐thiepin at 20°C.     

Rate Acceleration of the Baylis‐Hillman Reaction within Microreactors

Based on microreactors, the representative Baylis‐Hillman reaction of cyclopent‐2‐enone coupled with 4‐nitrobenzaldehyde in the presence of imidazole could be accelerated by manipulating the temperature and electric field. Furthermore, the electric field was used in promoting Baylis‐Hillman reaction for the first time with the rate acceleration approximately 5.2‐fold higher than that carried out in conventional vessels as well as 4.0‐fold under control of temperature. Meanwhile, the products of Baylis‐Hillman reaction at every time point could be collected and then determined by capillary micellar electrokinetic chromatography.     

Iron‐Catalyzed Allylic Amination Directly from Allylic Alcohols

Allylic amination, directly from alcohols, has been demonstrated without any Lewis acid activators using an efficient and regiospecific molecular iron catalyst. Various amines and alcohols were employed and the reaction proceeded through the oxidation/reduction (redox) pathway. A direct one‐step synthesis of common drugs, such as cinnarizine and nafetifine, was exhibited from cinnamyl alcohol that produced water as side product.     

Enantioselective Aldol Reactions Catalyzed by Chiral Phosphine Oxides

The development of enantioselective aldol reactions catalyzed by chiral phosphine oxides is described. The aldol reactions presented herein do not require the prior preparation of the masked enol ethers from carbonyl compounds as aldol donors. The reactions proceed through a trichlorosilyl enol ether intermediate, formed in situ from carbonyl compounds, which then acts as the aldol donor. Phosphine oxides activate the trichlorosilyl enol ethers to afford the aldol adducts with high stereoselectivities. This procedure was used to realize a directed cross‐aldol reaction between ketones and two types of double aldol reactions (a reaction at one/two α position(s) of a carbonyl group) with high diastereo‐ and enantioselectivities.     

Cooperative Catalysis by Palladium and a Chiral Phosphoric Acid: Enantioselective Amination of Racemic Allylic Alcohols

Cooperative catalysis by [Pd(dba)₂] and the chiral phosphoric acid BA1 in combination with the phosphoramidite ligand L8 enabled the efficient enantioselective amination of racemic allylic alcohols with a variety of functionalized amines. This catalytic protocol is highly regio‐ and stereoselective (up to e.r. 96:4) and furnishes valuable chiral amines in almost quantitative yield.     

Transformations of Modified Morita‐Baylis‐Hillman Adducts from Isatins Catalyzed by Lewis Bases

The development of synthetic protocols to access architectures with broad structural and functional diversity from readily available starting materials is very attractive in both organic and medicinal chemistry fields. Toward this objective, the multifunctional isatin‐derived Morita‐Baylis‐Hillman (MBH) adducts provide opportunities to construct a variety of complex scaffolds containing a “privileged” oxindole motif through several catalytic pathways. By forming the ammonium or phosphonium salts with Lewis bases, isatin‐derived MBH adducts can undergo allylic substitutions with a range of nucleophiles, usually in a S_N2′‐S_N2′ pattern. Besides, assisted by Brønsted bases, the corresponding onium salts can be converted into the allylic ylide intermediates, which can undergo various annulation reactions or even 1,3‐difunctionalizations. Moreover, recent cooperative catalysis of Lewis bases and transition metal complexes further puts forward the application of isatin‐derived MBH adducts. This tutorial review covers the significant transformations of isatin‐derived MBH adducts, mostly in an asymmetric version, catalyzed by various Lewis bases over the past decade.     

Dual Organocatalysis: Asymmetric Allylic–Allylic Alkylation of α,α‐Dicyanoalkenes and Morita–Baylis–Hillman Carbonates

The first highly enantioselective allylic–allylic alkylation of α,α‐dicyanoalkenes and Morita–Baylis–Hillman carbonates by dual catalysis of (DHQD)₂AQN and (S)‐BINOL has been investigated. Excellent stereoselectivities have been achieved for a broad spectrum of substrates (d.r. > 99:1, up to 99 % ee). The multifunctional allylic products could be efficiently converted to a range of complex chiral cyclic frameworks. EWG=electron‐withdrawing group, (DHQD)₂AQN=hydroquinidine (anthraquinone‐1,4‐diyl) diether, (S)‐BINOL =(S)‐(?)‐1,1′‐bi‐2‐naphthol.

     

从Baylis-Hillman溴化物方便的合成N-取代的咪唑和苯并三氮唑

在室温下, 通过Baylis-Hillman溴化物与咪唑或苯并三氮唑反应, 方便的合成了N-取代的咪唑和苯并三氮唑衍生物. 该方法的优点为操作简单, 反应条件温和, 产率高, 好的区域和立体选择性.     

Asymmetric Baylis–Hillman Reactions Promoted by Chiral Imidazolines

The coupling of electrophiles with activated alkenes by using tertiary amines or phosphines is generally known as the Baylis–Hillman reaction. It is a useful and atom‐economical carbon–carbon bond‐forming reaction that generates multifunctionalized products. This reaction is notoriously slow; yields are often low and substrate‐dependent. The asymmetric reaction is still limited especially for unactivated olefins such as acrylates. Imidazolines have been developed as ligands in metal‐catalyzed reactions and have also been used as privileged structures in diversity‐oriented synthesis. A series of novel chiral imidazolines were prepared and used to develop asymmetric Baylis–Hillman reactions. These imidazolines promote the reactions of various aromatic aldehydes with unactivated acrylates. Enantiomeric excesses of up to 60 % and high yields were obtained by using stoichiometric amounts of the promoter. Furthermore, the imidazolines are also suitable promoters for the reactions between aromatic aldehydes and alkyl vinyl ketones. Enantiomeric excesses of up to 78 % and high yields were obtained with 50 mol % of an imidazoline with a chiral methylnaphthyl group. These chiral imidazolines are easily prepared from commercially available amino alcohols and can be easily recovered for reuse without loss of product enantioselectivity.     

Chiral Phosphoric Acid Catalyzed Atroposelective C−H Amination of Arenes

N‐arylcarbazole structures are important because of their prevalence in natural products and functional OLED materials. C?H amination of arenes has been widely recognized as the most efficient approach to access these structures. Conventional strategies involving transition‐metal catalysts suffer from confined substrate generality and the requirement of exogenous oxidants. Organocatalytic enantioselective C–N chiral axis construction remains elusive. Presented here is the first organocatalytic strategy for the synthesis of novel axially chiral N‐arylcarbazole frameworks by the assembly of azonaphthalenes and carbazoles. This reaction accommodates broad substrate scope and gives atropisomeric N‐arylcarbazoles in good yields with excellent enantiocontrol. This approach not only offers an alternative to metal‐catalyzed C–N cross‐coupling, but also brings about opportunities for the exploitation of structurally diverse N‐aryl atropisomers and OLED materials.