Michael Addition of 3-Oxo-3-phenylpropanenitrile to Linear Conjugated Enynones: Approach to Polyfunctional δ-Diketones as Precursors for Heterocycle Synthesis

Reaction of linear conjugated enynones, 1,5-diarylpent-2-en-4-yn-1-ones [Ar¹C≡CCH=CHC(=O)Ar²], with 3-oxo-3-phenylpropanenitrile (NCCH₂COPh) in the presence of sodium methoxide MeONa as a base in MeOH at room temperature for 4–26 h affords polyfunctional δ-diketones as a product of regioselective Michael addition to the double carbon–carbon bond of starting enynones. The δ-diketones have been formed as mixtures of two diastereomers in a ratio of 2.5:1 in good general yields of 53–98%. A synthetic potential of the obtained δ-diketones has been demonstrated by heterocyclization with hydrazine into substututed 5,6-dihydro-4H-1,2-diazepine.     

Rhodium‐Catalyzed Regioselective N2‐Alkylation of Benzotriazoles with Diazo Compounds/Enynones via a Nonclassical Pathway

A novel rhodium‐catalyzed highly selective N²‐alkylation of benzotriazoles with diazo compounds/enynones is achieved, providing N²‐alkylated benzotriazoles in good to excellent yields and with excellent N² selectivities. Importantly, different to traditional carbene insertion into X?H (X=N, O etc) bonds, DFT calculations disclose that this selective N²‐alkylation probably proceeds through a formal 1,3‐ rather than 1,2‐H shift to give the final products.     

丙二腈在多组分反应中的应用*

丙二腈分子中的氰基作为强吸电子基团活化亚甲基,也是良好的离去基团,以及氰基的碳氮三键可进行加成反应,使得丙二腈是一种非常特别的化合物。它具有非常丰富的反应性质,可以发生Knoevenagel缩合、Michael加成、环化和消去等反应,是进行多组分合成反应的优良试剂。由其参加的多组分合成反应已经成为合成众多碳环和杂环化合物的重要方法。本文综述了丙二腈在多组分反应中的研究进展,介绍了近年来丙二腈参加的多组分反应合成环状化合物的成功事例,展望了丙二腈反应的发展方向。     

Reaction of Some Terpenoids with Malononitrile in the Presence of Hydrotalcite

α-Ionone and 5,5,8-trimethyl-3,7-nonadien-2-one react with malononitrile in the presence of specially prepared hydrotalcite to afford the corresponding Knoevenagel condensation products with high yield and selectivity.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 859–863.Original Russian Text Copyright © 2005 by Khomenko, Volcho, Toktarev, Echevskii, Salakhutdinov, Barkhash.     

Stereoselective Synthesis of Enamides through Palladium-Catalyzed Oxidative Amidation of Conjugated Olefins with 2-Pyridones

A palladium-catalyzed oxidative amidation of conjugated olefin with 2-pyridone is described. A series of E-Enamides were synthesized in a highly stereocontrolled manner. The reaction also accommodates other cyclic and acyclic amides. Z-Enamides were predominantly prepared for primary amides probably due to the presence of an intramolecular hydrogen bond. Gram-scale synthesis of enamide and the following oxidative annulation with diphenylacetylene demonstrates the synthetic utility of this reaction.     

Aryl-to-Vinyl 1,4-Nickel Migration/Reductive Cross-Coupling Reaction for the Stereoselective Synthesis of Multisubstituted Olefins

The aryl-to-vinyl nickel 1,4-migration (1,4-Ni migration) reaction has been reported for the first time. The generated alkenyl Ni species undergo a reductive coupling reaction with unactivated brominated alkanes affording a series of trisubstituted olefins. This tandem reaction exhibits mild conditions, a broad substrate scope, high regioselectivity, and excellent Z/E stereoselectivity. A series of controlled experiments have shown that the critical 1,4-Ni migration process is reversible. In addition, the alkenyl nickel intermediates obtained after migration are highly Z/E stereoselective and do not undergo Z/E isomerization. The obtained trace isomerization products are caused by the instability of the product.     

碱催化醛、丙二腈和邻苯二甲酰肼的、三组分反应合成酞嗪衍生物

经过实验验证引入水有利于芳香醛、丙二腈和邻苯二甲酰肼三组分的反应进行,催化量的有机碱三乙胺(Et 3 N)或无机碱磷酸氢二钾(K 2 HPO 4[DK1]·3H 2 O)可以在常规条件下促进该反应。本文以39%~97%的产率合成一系列1 H-吡唑[1,2-b]酞嗪-5,10-二酮衍生物。两种催化剂均溶于水,因此,反应结束后催化剂的分离与产物提纯简便易行。此方法具有反应条件温和、绿色环保、操作简单、后处理方便等特点。     

Direct Synthesis of Allyl Amines with 2-Nitrosulfonamide Derivatives via the Tsuji-Trost Reaction

The Tsuji-Trost Reaction is a palladium-catalysed allylation of nucleophiles that consists in the reaction of a nitrogen, carbon or oxygen-based nucleophiles with an allylic substrate bearing a leaving group. Here we present the use of 2-nitrosulfonamide derivatives as nucleophile, which are reactive under mild conditions. 2-nitrosulfonyl groups are well-known dual protective activator groups easy to introduce in any type of amine substrates. The resulting 2-nitrosulfonamide derivatives are ideal substrates for the Tsuji-Trost reaction to afford a convenient and flexible access to primary and dissymmetric secondary allyl amines. The optimised procedure is flexible (for solvent, temperature, functional groups) and has been applied with good to excellent yield to access to a wide range of allyl amine derivatives.     

Stereoselective Synthesis of Selenium-Containing Glycoconjugates via the Mitsunobu Reaction

A simple and efficient route for the synthesis of new glycoconjugates has been developed. The approach acts as a model for a mini-library of compounds with a deoxy-selenosugar core joined to a polyphenolic moiety with well-known antioxidant properties. An unexpected stereocontrol detected in the Mitsunobu key reaction led to the most attractive product showing a natural d-configuration. Thus, we were able to obtain the target molecules from the commercially available d-ribose via a shorter and convenient sequence of reactions.     

Photocontrolled Synthesis of n‐Type Conjugated Polymers

Current approaches to synthesize π‐conjugated polymers (CPs) are dominated by thermally driven, transition‐metal‐mediated reactions. Herein we show that electron‐deficient Grignard monomers readily polymerize under visible‐light irradiation at room temperature in the absence of a catalyst. The product distribution can be tuned by the wavelength of irradiation based on the absorption of the polymer. Conversion studies are consistent with an uncontrolled chain‐growth process; correspondingly, chain extension produces all‐conjugated n‐type block copolymers. Preliminary results demonstrate that the polymerization can be expanded to donor–acceptor alternating copolymers. We anticipate that this method can serve as a platform to access new architectures of n‐type CPs without the need for transition‐metal catalysis.     

A Nazarov-Ene Tandem Reaction for the Stereoselective Construction of Spiro Compounds

The different reactivity of trienones under Lewis and Brønsted acids catalysis was investigated, resulting in distinct cyclization products and carbon backbones that originated either from a conjugate Prins cyclization or an interrupted Nazarov cyclization. In particular, an unprecedented Nazarov cyclization tandem reaction is presented, terminating the oxyallyl cation by an ene-type reaction, and leading stereoselectively to bicyclic spiro compounds. The terminal olefin of this motif represents a useful handle for further functionalization, making it a strategic intermediate in total syntheses. The tandem Nazarov/ene cyclization was shown to be preferred over a Nazarov/[3+2] tandem reaction for all our substrates, independent of chain length. Deuteration studies further support the mechanistic hypothesis of the terminating ene reaction.     

One‐Pot Synthesis of Pentasubstituted Cyclohexanes by a Michael Addition Followed by a Tandem Inter–Intra Double Henry Reaction

Michael, Henry, and Henry : A new one‐pot reaction of α,β‐unsaturated aldehydes and β‐dicarbonyls, which involves a Michael reaction catalyzed by diarylprolinol ethers and an inter–intramolecular Henry tandem reaction catalyzed by TBAF (see scheme), has been developed. The reaction proceeds in high enantio‐ and diastereoselectivity for a wide range of unsaturated aldehydes and β‐dicarbonyl reagents.