The addition reaction of α-azido ethers and α-azido thioethers to phenylacetylene

Several v-triazoles were synthesized by 1,3-dipolar cycloaddition of certain α-azido ethers and α-azidothioethers to phenylacetylene. In most of the cases the reaction led to the formation of the two isomeric v-triazoles. Structural assignments for the products obtained were made on the basis of NMR data and chemical reactions. Characteristic differences between the NMR spectra of the isomers have been noted.     

Ionic-liquid-supported organocatalyst for the enantioselective Michael addition of ketones to nitroolefins

Ionic-liquid-supported triazole-pyrrolidine 2, for the direct asymmetric Michael reaction was successfully synthesized. The supported catalyst demonstrated good activity and high enantioselectivity in the addition of cyclohexanone to nitroolefins. Furthermore, the supported catalyst can be readily recovered and reused four times without significant loss of catalytic activity.     

Sugar amide-pyrrolidine catalyst for the asymmetric Michael addition of ketones to nitroolefins

New sugar amide-pyrrolidine derivatives possessing the furano form of the carbohydrate template were designed and developed as efficient and stereoselective organocatalysts for asymmetric Michael additions of ketones to nitroolefins at room temperature. Good yields and high selectivities were achieved with catalyst 2 under solvent-free and additive-free reaction conditions.     

Highly efficient bifunctional organocatalysts for the asymmetric Michael addition of ketones to nitroolefins

A type of secondary-secondary-tertiary triamine bifunctional organocatalysts have been properly designed and synthesized. In our study, the designed catalyst (S)-N-(pyrrolidin-2-ylmethyl)pyridin-2-amine 5 has been shown to be highly efficient to promote the asymmetric Michael addition of ketones to nitroolefins at room temperature, which afforded the corresponding adducts in excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to >99% ee).     

A highly enantioselective organocatalyst for the Michael addition of cyclic ketones to nitroolefins

Enantiomerically pure triamine 2, which catalyses the Michael addition of cyclic ketones to nitroolefins with high diastereoselectivity (up to 99:1) and enantioselectivity (up to 91% ee), was designed and prepared.     

Enantioselective Michael addition of cyclic ketones to nitroolefins catalyzed by a novel fluorine-insertion organocatalyst

A novel fluorine-insertion organocatalyst, which was designed based on the fluorine–ammonium ion gauche effect, was synthesized and used successfully to catalyze the asymmetric Michael addition of cyclic ketones to nitroolefins. High yields and excellent diastereo- and enantioselectivities were achieved under mild conditions. A possible stereochemical model is also proposed.     

Pyrrolidine-oxyimides: new chiral catalysts for enantioselective Michael addition of ketones to nitroolefins in water

A new class of proline based organocatalysts ‘pyrrolidine-oxyimides’ were designed and synthesized from l-proline and hydroxyimides by employing a simple reaction protocol. These catalysts were found to be efficient in promoting asymmetric Michael additions of ketones to nitroolefins at room temperature. Good yields and high selectivities were obtained with catalyst 1a under additive-free conditions employing water as the reaction medium.     

Chiral squaramide as multiple H-bond donor organocatalysts for the asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroolefins

A series of chiral bifunctional squaramide multiple H-bond donor organocatalysts have been designed and synthesized by the rational assembly of chiral privileged scaffolds of indanol and cinchona alkaloids. In the presence of 1 mol % 1a, the asymmetric Michael addition reaction of 1,3-dicarbonyl compounds to nitroolefins proceeded to provide the product in high yields (up to 92%) and with good to high ee values (up to 96%). The additional H-bond in this squaramide system plays a crucial role in enhancing the enantioselectivity.     

Highly enantioselective Michael addition of ketones to nitroolefins catalyzed by (S)-pyrrolidine arenesulfonamide

A new type of catalyst for the asymmetric Michael addition reaction has been designed and synthesized. This catalyst, (S)-pyrrolidine arenesulfonamide 1, resulted in high yields (up to 93%), excellent diastereoselectivities (syn/anti ratio up to 99/1), and excellent enantioselectivities (ee up to 99%) for various cyclic ketones and nitroolefins.     

Chiral phosphoproline-catalyzed asymmetric Michael addition of ketones to nitroolefins: an experimental and theoretical study

A novel pyrrolidine-based chiral phosphoproline is an effective bifunctional organocatalyst for the asymmetric Michael addition of ketones to nitroolefins giving high levels of diastereo- and enantio-selectivities (up to > 99 : 1 dr and 96% ee). anti-SR Transition state has the lowest barrier which controls the stereoselectivity, in agreement with experimental results.     

Pyrrolidine-carbamate based new and efficient chiral organocatalyst for asymmetric Michael addition of ketones to nitroolefins

The novel ((S)-pyrrolidin-2-yl)methyl phenylcarbamate was synthesized and used as an efficient organocatalyst for the asymmetric Michael addition of cyclic/acyclic ketones to nitroolefins. Interestingly, the resulting Michael adducts were obtained in good to high yields (up to 96%) with excellent stereoselectivity (ee up to >99%, dr up to >99:1) without using any additive.     

Enantioselective synthesis of α-amino ketones through palladium-catalyzed asymmetric arylation of α-keto imines

Chiral α-amino ketones are common structural motifs in natural products and pharmaceuticals, as well as important synthons in organic synthesis. Thus, establishing efficient methods for preparing compounds with these privileged scaffolds is an important endeavor in synthetic chemistry. Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones through a chiral palladium-catalyzed arylation reaction of in situ generated challenging α-keto imines from previously unreported C-acyl N-sulfonyl-N,O-aminals, with arylboronic acids. The current reaction offers a straightforward approach to the asymmetric synthesis of acyclic α-amino ketones in a practical and highly stereocontrolled manner. Meanwhile, the multiple roles of the chiral Pd(ii) complex catalyst in the reaction were also reported.

Chiral α-amino ketones are common structural motifs in natural products and pharmaceuticals, as well as important synthons in organic synthesis.     

A new type of organocatalyst for highly stereoselective Michael addition of ketones to nitroolefins on water

(S)-2-((Naphthalen-2-ylsulfonyl)methyl)pyrrolidine, prepared in three steps from (S)-N-Boc-2-[((4-toluenesulfonyl)oxy)methyl]pyrrolidine in 62% overall yield, was used as a new type of organocatalyst bearing a pyrrolidine and a sulfone moiety. It shows very high catalytic activity toward the direct asymmetric Michael reaction of cyclohexanone and nitroolefins. All the corresponding adducts can be furnished in 90-99% yields and with up to 98% ee and over 99:1 dr on water in the presence of this catalyst (15 mol %) without any additive.     

Organocatalytic Michael addition of aldehydes to trisubstituted nitroolefins

The combination of O-TMS protected diphenyl-prolinol and benzoic acid was found to be effective to catalyze the Michael addition of aldehydes to 3-substituted 3-nitroacrylates. The reaction provided syn,anti-Michael adducts with good diastereoselectivity and excellent enantioselectivity. Some β-aryl and α-methyl substituted nitroolefins also worked under these conditions, although prolonging reaction time was required. These adducts could be used for assembling 2,3,4-trisubstituted pyrrolidines through simple hydrogenation.     

Organocatalytic asymmetric azidation of sulfoxonium ylides: mild synthesis of enantioenriched α-azido ketones bearing a labile tertiary stereocenter

Disclosed here is a catalytic asymmetric azidation reaction for the efficient synthesis of α-azido ketones bearing a labile tertiary stereocenter. With a superb chiral squaramide catalyst, a mild asymmetric formal H–N₃ insertion of α-carbonyl sulfoxonium ylides proceeded with excellent efficiency and enantioselectivity. This organocatalytic process not only complements the previous α-azidation approaches for the formation of quaternary stereocenters and mostly for 1,3-dicarbonyl compounds, but also has advantages over the well-known metal-catalyzed asymmetric carbene insertion chemistry using α-diazocarbonyl compounds. Detailed mechanistic studies via control reactions and NMR studies provided important insights into the reaction pathway, which features reversible protonation and dynamic kinetic resolution. The curiosity in mechanism also led to the development of a simplified alternative protocol with a cheaper HN₃ source.

An organocatalytic asymmetric H–N₃ insertion of α-carbonyl sulfoxonium ylides has been developed, providing efficient access to α-azido ketones bearing labile tertiary stereocenters and complementing the metal carbene insertion chemistry.     

1,4-Conjugate addition of allyltrimethylsilane to α,β-unsaturated ketones

α,β-Unsaturated ketones smoothly undergo conjugate addition with allyltrimethylsilane in the presence of a catalytic amount of elemental iodine under very mild and convenient conditions to afford the corresponding Michael adducts in high yields with high selectivity.     

Michael addition of dimedone with α,β‐unsaturated ketones: Synthesis of quinoline and chromene derivatives

A series of quinoline and chromene derivatives has been synthesized by Michael addition of dimedone 1 with 2‐aroyl‐3‐arylacrylonitrile 2 and study of absorption and fluorescence maxima of quinolines.     

Trityl Cation-Catalyzed Hosomi-Sakurai Reaction of Allylsilane with β,γ-Unsaturated α-Ketoester to Form γ,γ-Disubstituted α-Ketoesters

(Ph₃C)[BPh(^F)₄]-catalyzed Hosomi-Sakurai allylation of allylsilanes with β,γ-unsaturated α-ketoesters has been developed to give γ,γ-disubstituted α-ketoesters in high yields with excellent chemoselectivity. Preliminary mechanistic studies suggest that trityl cation dominates the catalysis, while the silyl cation plays a minor role.     

Organocatalytic asymmetric Michael addition of 2,4-pentandione to nitroolefins

[reaction: see text] A novel binaphthyl-derived amine thiourea organocatalyst has been developed and demonstrated to efficiently catalyze Michael addition reactions (using as low as 1 mol % loading) of diketones to nitroalkenes with remarkably high enantioselectivities.     

镍催化α,β-不饱和醛的选择性α,β-双芳基化反应

三组分双官能化反应是一种高效、简便构建C―C键、C―X键的方式. 双键广泛存在于众多有机化合物中, 对双键的双官能化反应研究有巨大的应用潜力. 本工作以Ni(COD)₂为催化剂, 以芳基溴化镁、芳基溴化物为芳基化试剂, 实现了3-芳基-2-丙烯醛亚胺中碳碳双键的双芳基化反应. 该反应建立了一个新的镍催化α,β-不饱和醛的α,β-双芳基化方法, 可以高度区域选择性地向底物分子中引入两个不同取代的芳环, 得到多种2,3,3-三芳基丙醛骨架的产物. 利用这一反应作为核心步骤实现了天然产物Quebecol的简便合成. 机理研究表明, 该反应可能经历了亲核加成、金属交换、还原消除的历程.