L‐Lysine/imidazole‐catalyzed Multicomponent Cascade Reaction: Facile Synthesis of C5‐substituted 3‐Methylcyclohex‐2‐enones

A facile and simple route for the direct preparation of substituted 3‐methylcyclohex‐2‐enone via Aldol‐Robinson cascade reaction of aldehydes and acetones catalyzed by the new catalytic system of L‐lysine/imidazole in n‐heptane with 0.5% water was reported. A variety of substrates can participate in the process efficiently. The merits of this method included inexpensive and easily available starting materials and catalyst, the good yield of products and the straightforward work‐up.     

Imidazole‐catalyzed Three‐component Cascade Reaction for the Facile Synthesis of Highly Substituted 3,4‐Dihydropyridin‐2‐one Derivatives

A novel one‐pot protocol for the synthesis of valuable 3,4‐dihydropyridin‐2‐ones from the condensation of aldehyde with cyanoacetamide and 1,3‐dicarbonyl compounds in the presence of imidazole was developed. A series of aldehydes and 1,3‐dicarbonyl compounds were employed to examine the scope of substrates for this protocol. This reaction proceeded through the formation of one ring and four new bonds (two C? C, one C? N, one C?C) via the sequence involving Knoevenagel condensation, Michael addition and intramolecular cyclization with moderate to excellent yields. All new compounds were characterized by IR, ¹H NMR, ¹³C NMR and HRMS.     

Enantioselective Multicomponent Synthesis of Fused 6–5 Bicyclic 2‐Butenolides by a Cascade Heterobicyclisation Process

The successive coupling of an alkoxy(aryl/heteroaryl)carbene complex of chromium with either a ketone or an imide lithium enolate and then a 3‐substituted (H, TMS, PhCH₂, PhCH₂CH₂, Me) propargylic organomagnesium reagent has afforded novel hydroxy‐substituted bicyclic [4.3.0]‐γ‐alkylidene‐2‐butenolides with three modular points that has allowed the efficient introduction of molecular complexity, including a homopropargylic alcohol core. The selective formation of these five‐ or six‐component heterobicyclisation products is the result of the regioselective integration of the Grignard reagent as a propargyl fragment followed by a cascade CO/alkyne/CO insertion, ketene trapping and elimination sequence. By using lithium enolates of chiral N‐acetyl‐2‐oxazolidinones and the corresponding propargylic organocerium reagents, both enantiomers of these bicyclic heterocycles were efficiently prepared with very high enantiomeric purity. Architecturally, these fused bicyclic butenolides are characterised by a highly unsaturated and oxygenated core and they exhibit strong blue fluorescence in solution.     

Cover Picture: Benzene Triimides: Facile Synthesis and Self‐Assembly Study (Chin. J. Chem. 7/2019)

The cover picture shows an efficient one‐pot condensation of maleimide derivatives in the presence of acetic acid and water to afford a series of benzene triimides (BTIs). The structure, physicochemical properties and electrochemistry behavior of BTIs were systematically investigated. Owing to the planar structure and unique electron‐deficient nature, BTIs can self‐assemble into different motifs. More details are discussed by Wang et al. on page 684–688.

     

Cover Picture: Organocatalytic Domino Michael–Knoevenagel Condensation Reaction for the Synthesis of Optically Active 3‐Diethoxyphosphoryl‐2‐oxocyclohex‐3‐enecarboxylates (Chem. Eur. J. 13/2009)

In Buddhist imagery the gestures of the hand are very significant, which reflects the themes of asymmetry and chirality (derived from the word “hand”) found in the Full Paper by K. A. Jørgensen et al. on page 3093 ff. The professor is shown as a Buddha‐like image and is gesturing down with one hand and making the Buddhist gesture for “method and wisdom” with the other. Dice tumbling from his hand represent the organocatalytic Michael–Knoevenagel condensation domino reaction discussed in the paper, with the front die representing the cyclohexenone center of the molecule being formed. The two students standing by are making Buddhist gestures for “accomplishment” and “meditation”. Artwork by cartoonist Jorge Cham, http://www.phdcomics.com.

     

Facile Synthesis of Chiral Spirooxindole‐Based Isotetronic Acids and 5‐1H‐Pyrrol‐2‐ones through Cascade Reactions with Bifunctional Organocatalysts

Unprecedented organocatalyzed asymmetric cascade reactions have been developed for the facile synthesis of chiral spirooxindole‐based isotetronic acids and 5‐1H‐pyrrol‐2‐ones.The asymmetric 1,2‐addition reactions of α‐ketoesters to isatins and imines by using an acid–base bifunctional 6′‐OH cinchona alkaloid catalyst, followed by cyclization and enolization of the resulting adducts, gave chiral spiroisotetronic acids and 5‐1H‐pyrrol‐2‐ones, respectively, in excellent optical purities (up to 98 % ee). FT‐IR analysis supported the existence of hydrogen‐bonding interaction between the 6′‐OH group of the cinchona catalyst and an isatin carbonyl group, an interaction that might be crucial for catalyst activity and stereocontrol.