Intramolecular Diels-Alder reaction of α-fluoroacrylate derivatives promoted by novel bidentate aluminum Lewis acid

Intramolecular Diels-Alder (IMDA) reaction of α-fluoroacrylate derivatives 1a-e having 1,7,9-decatrienoate system is efficiently promoted by the novel bidentate Lewis acid A generated in situ by mixing 3,3′,5,5′-tetrabromo-1,1′-biphenyl-2,2′-diol (Br₄BIPOL, 1 mol) and trimethylaluminum (2 mol). The IMDA reaction of α-fluoroacrylates proceeds via endo-boat transition state as in the case of the corresponding non-fluorinated acrylate.     

Ugi/Diels-Alder串联反应在构建杂环化合物中的应用

杂环化合物广泛存在于天然产物和药物分子中,许多杂环化合物还具有潜在生物活性和药理作用。因此,如何快速高效地构建小分子杂环化合物库成为当今有机合成和药物化学领域的研究热点。Ugi反应在多样性导向合成方面具有得天独厚的优势,能够解决待合成化合物数量庞大、结构复杂的难题;同时,Diels-Alder [4+2]环加成反应能够高效构建碳-碳键,以较高的立体选择性和区域选择性合成六元环系。目前,集二者于一身的Ugi/Diels-Alder串联反应在构建杂环化合物方面展现出了巨大优势和无穷潜能。本文以不同类型的DA反应分类:按照呋喃作为双烯体、吡咯作为双烯体、噻吩为双烯体、口恶唑作为双烯体、 1,2,4-三嗪作为双烯体、苯作为双烯体、不饱和键和芳环共同作为双烯体等对UDA串联反应的研究进行了综述。     

Intramolecular reaction of polymer coordinated cationic rhodium complex

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Efficient microwave-assisted synthesis of fused benzoxazepine–isoquinoline derivatives via an Ugi reaction/tautomerization/intramolecular SNAr reaction sequence

A series of compounds containing the benzoxazepine-isoquinoline scaffold was synthesized in a one-pot procedure via an Ugi reaction followed by tautomerization reaction between the keto and enol forms and intramolecular nucleophilic substitution. The microwave-assisted strategy allowed the facile synthesis of a library of target compounds and is applicable to the construction of diverse libraries of related compounds for high throughput screening in medicinal chemistry.     

Intramolecular Diels-Alder cycloaddition/rearrangement cascade of an amidofuran derivative for the synthesis of (±)-minfiensine

An efficient synthesis of (±)-minfiensine has been accomplished employing an intramolecular Diels-Alder cycloaddition/rearrangement cascade of an amidofuran derivative. Thermal reorganization of the initially formed [4+2]-cycloadduct affords the critical tetrahydroiminoethanocarbazole skeleton of the alkaloid in high yield.     

One-pot synthesis of oxoisoindoline-1,2,3-triazole hybrid by a Ugi–click reaction

1,2,3-Triazole-3-oxoisoindoline-1-carboxamide system was successfully synthesized by using a combination of Ugi and click reactions. This two-step, one-pot synthesis was started by the reaction of 2-formyl benzoic acid, propargyl amine, and cyclohexyl isocyanide in ethanol. The resultant Ugi adduct underwent a copper-catalyzed click reaction, producing the desired products in good yields.     

Diels-Alder reaction with phosphaalkenes. Synthesis of functionalized λ3 phosphabenzenes.

The reaction of phosphaalkenes (1 and2) with 1,3 dienes such as methyl sorbate and 1-methoxy 3-trimethylsilyloxy-1,3 butadiene leads to functionalized λ³ phosphabenzenes6,9,12,13 and16 after aromatization of the primary adducts. The aromatization may occur either spontaneously or after chemical transformations. The reversible cycloaddition has allowed the synthesis of isomeric phosphabenzenes6 and9. Diels-Alder reaction with phosphaalkenes appears to be a general method for the obtention of functionalized λ³ phosphabenzenes.     

Inclusion property and Diels-Alder reaction of bis (diphenylphosphine oxide) butadiyne

The host molecule, bis (diphenylphosphine oxide) butadiyne (2), includes a variety of guests to form five complexes (2a-2e). In addition, the Diels-Alder reaction between 2 and anthracene gives 9, 9', 10, 10'-tetrahedron-9, 9', 10, 10'-bi-ethenoantracene-11, 11'-bis ( diphenylphosphine oxide) (3) which is a potential di-π-methane reactant and can undergo photorearrangement.     

N-Isocyanodialkylamines generated in situ for the Joullié–Ugi reaction with indolenines

N-Isocyanodialkylamines are rare isocyanide surrogates for the Ugi-type reactions. To avoid problems with instability and the obnoxious smell of these reagents, we optimized and employed a convenient protocol for in situ dehydration of N,N-dialkyl-N′-formyl hydrazines to give the respective N-isocyanodialkylamines which were utilized in the reaction with indolenines and acetic acid. The reaction was demonstrated to give modest to excellent yields of products incorporating the N-isocyanodialkylamine but not the carboxylic acid component.     

Development of a stereoselective Ugi reaction starting from an oxanorbornene β-amino acid derivative

We have synthesised a novel oxanorbornene β-aminoacid derivative and employed it in a stereoselective Ugi reaction. Hypothesis regarding the mechanism taking place during the reaction have been made and validated through the determination of the relative and absolute configuration of the Ugi adducts. Use of the correct choice of solvents can increase stereoselection. The resulting bicyclic peptidomimetics can be used as a novel class of pluripotent substrates to be elaborated according to the synthetic strategies previously elaborated in our laboratories.     

Intramolecular Diels–Alder reaction for the synthesis of tetracyclic carbazoles and isocanthines

One pot intramolecular Diels–Alder reaction has been efficiently used as a new route for the synthesis of four tetracyclic carbazoles and four isocanthine analogues where a dialdehyde is utilised as a common intermediate for both the scaffolds. Biological activity was evaluated for some molecules, which demonstrated moderate activity against HeLa cervical cancer cell lines.     

Synthesis of bridgehead-functionalized triptycene quinones via Lewis acid–promoted Diels-Alder reaction of 9-acyloxyanthracenes

Herein, we show that bridgehead-functionalized triptycene quinones can be rapidly and conveniently prepared in good to high yields by Lewis acid–catalyzed cycloaddition of 1,4-benzoquinones and 1,4-naphthoquinones to 9-acyloxyanthracenes and probe the substrate scope of this transformation.     

The Ugi reaction with CF3-carbonyl compounds: effective synthesis of α-trifluoromethyl amino acid derivatives

The Ugi reaction with CF₃-carbonyl compounds is described in detail. The method is efficient for the multicomponent preparation of α-trifluoromethyl (Tfm) amino acids, α-Tfm containing dipeptides, and iminodicarboxylic acids. In addition, the first protected CF₃-opine derivative was prepared. The scope, limitations, and stereochemistry of the approach are discussed.     

Quantum chemical study on the thermal Diels-Alder reaction of cyclohexadiene and methyl crotonate

AM1 molecular orbital method using the unrestricted Hartree-Fock(UHF) calculations has been applied to investigate the thermal reaction of cyclohexadiene and methyl crotonate. The calculated results indicate that the thermal Diels-Alder reaction proceeds to product through the concerted path and two radical pathways.     

Amino-β-lactams in Ugi reaction: An efficient method for preparation of functionalized peptidomimetics

A synthetic strategy for the Ugi reaction on amino-β-lactam synthon 1 was developed. The Ugi reaction products 5 were obtained in satisfactory yields (47–78%) and generally, low diastereoselectivity (up to 72:28 dr). In case of Ugi products 5 derived from cyclohexylcarbaldehyde and amino-β-lactam 1, the reaction yields were lower (38–61%) but the products were obtained in high diastereoselectivity (>95:5).     

Lateral extension of π conjugation along the bay regions of bisanthene through a Diels-Alder cycloaddition reaction

Diels-Alder cycloaddition reactions at the bay regions of bisanthene (1) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addition followed by reductive aromatization reactions to afford the laterally extended bisanthene derivatives 2 and 3. Attempted synthesis of a larger expanded bisanthene 4 revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addition was observed on quinone 14, which was obtained by Diels-Alder reaction between 1 and 1,4-anthraquinone. Compounds 1-3 exhibited near-infrared (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by density function theory and non-planar twisted structures were calculated for 2 and 3. All compounds showed amphoteric redox behavior with multiple oxidation/reduction waves. Oxidative titration with SbCl(5) gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures.     

Diels-Alder reaction of optically active (E)-γ-keto-α,β-unsaturated p-tolylsulfoxides with cyclopentadiene

The Diels-Alder reaction of enantiomerically pure (E)-γ-keto-α,β-unsaturated p-tolylsulphoxides 3 with cyclopentadiene give four easily separable diastereomers. The effect of several Lewis acids on the reaction was studied, finding a high endo selectivity with respect to the carbonyl group and moderate π-diastereoselectivity using BF₃·Et₂O as catalyst. The reactivity of compounds 3 as well as their endo selectivity are both higher than those observed for the corresponding (E)-3-sulfinylacrylates.     

Enantioselective organocatalytic Friedel-Crafts alkylation reaction of indoles with 5-hydroxyfuran-2(5H)-one: access to chiral γ-lactones and γ-lactams via a Ugi 4-center 3-component reaction

5-Hydroxyfuran-2(5H)-one 1, a readily available renewable resource, was used as an electrophile in the Friedel-Crafts alkylation of indoles catalyzed by a diphenylprolinol silyl ether. Moderate catalyst loading was achieved because of the high reactivity of 5-hydroxyfuran-2(5H)-one 1 in this process. Reduction of the Friedel-Crafts adduct (FC adduct) afforded indoyl lactones in high yield and enantioselectivity. Moreover, the FC adduct was used as a chiral synthon in a diversity-oriented synthesis, as illustrated by its successful engagement in a 4-center 3-component Ugi reaction (U-4C-3CR) to afford chiral five-membered lactams in high yield and enantioselectivity.     

The reaction of N-phenyldialkynylimines with η5-cyclopentadienyldicarbonylcobalt

N-Substituted dialkynylimines react with η⁵-cyclopentadienyldicarbonylcobalt to give a mixture of η⁴-cyclobutadiene cobalt complexes, the structures of which have been determined by X-ray crystallography.