Microwave‐Assisted Facile Synthesis and Crystal Structure of cis‐9,10,11,15‐Tetrahydro‐9,10[3′,4′]‐furanoanthracene‐12,14‐dione

A facile synthesis and crystal structure of cis‐9,10,11,15‐tetrahydro‐9,10[3′,4′]‐furanoanthracene‐12,14‐dione from the reaction of anthracene and maleic anhydride in xylene in a short time and high yield using a modified commercial domestic microwave oven is reported.     

Oxidative Dearomatization: Synthesis of Functionalized Bicyclo[2.2.2]octenones,Sigmatropic Shift in Excited State,and Radical-Induced Cleavage of Cyclopropane Ring

Synthesis of novel bicyclo[2.2.2]octenones endowed with a β,γ-enone system in which γ-carbon is substituted with an electron-withdrawing group from simple aromatics is described. Oxa-di-pi-methane reaction of bicyclo[2.2.2]octenones to functionalized bicyclo[3.3.0]octanes and their transformation to bicyclo[3.2.1]octane framework are also presented.     

Synthesis of Six-Membered Functionalized Carbocyclic Compounds by One-Pot Reaction of Hydroquinone Derivatives and Dienes

A general method for one-pot reaction of hydroquinone derivatives and dienes has been developed. The system of Pb₃O₄ in tetrahydrofuran–trifluoroacetic acid was found to play dual roles as oxidant for the generation of quinones in situ and as catalyst for the Diels–Alder cycloaddition, which makes the one-pot reaction efficient and easy to carry out. Using this method, a variety of six-membered functionalized carbocyclic compounds can be easily prepared in medium to excellent yields at room temperature.      

Phytochemicals from Echinacea and Hypericum: A Direct Synthesis of Isoligularone

Reaction of trienes with α,β‐unsaturated aldehydes produces bicyclic products via a tandem Diels–Alder/ene reaction. The adduct from tiglic aldehyde was converted into isoligularone by conversion to a furan followed by benzylic oxidation.     

Catalyst‐Free One‐Pot Synthesis of 2,4,6‐Triaryl‐1,4‐dihydropyridines in Ionic Liquid and Their Catalyzed Activity on Two Simple Diels–Alder Reactions

A series of 2,4,6‐triaryl‐1,4‐dihydropyridines bearing a hydroxyl group was synthesized greenly by the cascade aldol/Michael/addition reaction of aromatic aldehyde, acetophenone, and NH₄OAc (1:2:excessive) in ionic liquid [BmIm][BF₄] without any catalyst. The results of their catalyzed activity on two simple Diels–Alder reactions indicated that this kind of compound containing a poly aryl ring can be used as an effective catalyst on the Diels–Alder reaction. This method, because of its environmental friendliness, simplicity, mild conditions, effectiveness, and lower costs, is suitable for the synthesis of arrays of compounds.     

级联反应以及双环[2,2,2]辛烯酮的合成

研究了合成桥环化合物1的级联反应,不仅得到已知桥环化合物1,还得到了具有双环[2.2.2]辛烯酮的新桥环化合物2以及两个新的烯丙基取代的呫吨酮3和4。并对可能的反应机理进行了解释。     

Synthesis of an Advanced Precursor of Demethoxyviridin

The synthesis of a potential precursor 3 to demethoxyviridin (1b) is described. The centerpiece of this strategy was the conversion of the previously described dibromoolefin 6 to the masked alkyne β-hydroxyaldehyde 5 in a single step. Further elaboration then produced the alkyne oxazole 4, which on thermolysis, followed by in situ tautomerization and silylation, led directly to 3.

Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for full experimental and spectral details.     

Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I

Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.     

Facile Synthesis of Spiro Oxindoles,Azaoxindoles, and Dihydroisoquinolone

Formation of 1-aryl-4-oxo-cyclohexa(e)nonecarboxylates from the Diels–Alder cycloaddition of 2-trimethylsilyloxy-1,3-butadiene and Danishefsky diene with aryl- and pyridylacrylates and further conversion thereof to spirocycles is described. This provides an efficient method for spiro oxindoles, azaoxindoles, and dihydroisoquinolones.

A Negishi cross-coupling reaction enables the total synthesis of (+)-stachyflin

We present a full account on the development of the total synthesis of the antiviral meroterpenoid (+)-stachyflin. The decalin subunit is rapidly accessed by an exo-selective Diels–Alder reaction, whereas the isonindolinone was synthesized via a highly efficient and practical de novo route starting from dimedone. A challenging sp²–sp³ Negishi cross-coupling reaction enabled construction of the crucial C15–C16 bond that connects the arene with the decalin subunit. For the final installation of the cis-decalin framework, a Lewis acid-catalyzed cyclization was applied.     

Theoretical Evaluation of the Global and Local Electrophilicity Patterns to Characterize Hetero Diels-Alder Cycloaddition in the Synthesis of Isoxazolo[4,5-e](1,2,3,4-tetrazine)

A series of substituted dienophiles 1—10 and three 1,2-diazadienes namely D-1, D-2, D-3 were chosen to understand the reactivity and selectivity of Diels-Alder cycloaddition. The global and local electrophilicity patterns have been evaluated on a series of cycloaddition reactions to assess the reaction pathways (NDAC/IEDDAC) using the absolute scale of electrophilicity proposed by Parr et al. Regional electrophilicity at the active sites of the reagents involved in Diels-Alder processes has been described on a quantitative basis using local or regional electrophilicity index i.e. Fukui function. Good qualitative/quantitative comparison was found between molecular energy gaps and global electronic parameters, which has been employed to assess the cycloaddition pathways successfully.     

Efficient Synthesis of Hexahydrocarbazoles

Selective reduction of the nitro group in methyl 1-(2-nitrophenyl)-4-oxo-cyclohex-2-enecarboxylates with zinc-acetic acid forms hexahydrocarbazoles. The reaction is applicable to the corresponding pyridyl analogs to generate azahexahydrocarbazoles. This provides an efficient method for the generation of tricyclic framework.

Synthesis and Characterization of Benzenesulfonyl Hydrazones and Benzenesulfonamides

In the search for structural cyclic imide analogues of therapeutic interest, the syntheses and characterization of benzenesulfonyl hydrazones and benzenesulfonamides are described. The benzenesulfonyl chlorides (2) and (3) were obtained through the Diels–Alder reaction between N‐p‐chloro‐sulfonylfenylmaleimide (1) and furan or 2‐methylfuran. The reactions of (2) and (3) with hydrazine and amines afforded the hydrazides and sulfonamides, respectively. The sulfonylhydrazones were obtained through a condensation between the sulfonylhydrazides with different benzaldehydes.     

离子液体及其在有机合成中应用

离子液体作为绿色替代溶剂可用来进行Diels-Alder反应、Friedel-Crafts反应、过渡金属催化反应、镜像选择烷基化等反应。该文综述近年来离子液体在这些反应中应用的进展。     

Enantioselective Redox-Divergent Chiral Phosphoric Acid Catalyzed Quinone Diels–Alder Reactions

An efficient enantioselective construction of tetrahydronaphthalene-1,4-diones as well as dihydronaphthalene-1,4-diols by a chiral phosphoric acid catalyzed quinone Diels–Alder reaction with dienecarbamates is reported. The nature of the protecting group on the diene is key to the success of achieving high enantioselectivity. The divergent “redox” selectivity is controlled by using an adequate amount of quinones. Reversible redox switching without erosion of enantioselectivity was possible from individual redox isomers.     

Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane

The reductive coupling reaction of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane 3 was carried out using TiCl₄-Zn in pyridine followed by a McMurry coupling reaction to afford the compounds anti and syn 1,2-dimethyl[2.4]MCP-1-ene 4. Bromination of 4 with BTMA-Br₃ in dry CH₂Cl₂ afforded the interesting compound 1,2-bis-(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-1-ene 6 and consecutive debromination with Zn and AcOH in CH₂Cl₂ solution afforded the stable solid 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 in 89% yield. Compound 7 was conveniently employed in a Diels–Alder reaction with dimethyl acetylenedicarboxylate (DMAD) to provide 2-(3′,6′-dihydrobenzo)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-4′,5′-dimethylcarboxylate 8 in good yield. Diels–Alder adduct 8 was converted into a novel and inherently chiral areno-bridged compound [2.4]MCP 9 by aromatization. The chirality of the two conformers was characterized by circular dichroism (CD) spectra of the separated enantiomer which are perfect mirror images of each other.     

HIGHLY DEOXYGENATED SUGARS. I. C2-BRANCHED GLUCOSE DERIVATIVES AND CARBON LINKED DEOXYGENATED DISACCHARIDES *

Triacetylglucal (1) is converted with high α-selectivity (>9:1) to the corresponding 2,3-unsaturated allyl and benzyl glycosides 2 and 3 using ferric chloride as the catalyst. The 6-O-silyl-protected allylic alcohol 5 is transformed to the 3,4-unsaturated C2-branched ester 6 or the amide 7 by Claisen rearrangement. The highly deoxygenated iodo lactone 8, resulting from the amide 6 by iodolactonization, is a versatile starting material for chiral building blocks 9–12. The 3,4-unsaturated C2-branched ester 6 is reduced to the aldehyde 14 and converted to a carbon linked disaccharide analogue 16 via cycloaddition with Danishefky's diene.     

Enantioselective Synthesis of cis-Decalin Derivatives by the Inverse-Electron-Demand Diels–Alder Reaction of 2-Pyrones

A novel strategy for the synthesis of cis-decalins by an ytterbium-catalyzed asymmetric inverse-electron-demand Diels–Alder reaction of 2-pyrones and silyl cyclohexadienol ethers is reported here. A broad range of synthetically important cis-decalin derivatives with multiple contiguous stereogenic centers and functionalities are obtained in good yields and stereoselectivities. A full set of diastereomeric substituted cis-decalin motifs are readily accessible by tuning the absolute configurations of substituted silyl cyclohexadienol ethers (R or S) as well as the ligands (R or S). The synthetic potential is showcased by the enantioselective total synthesis of 4-amorphen-11-ol, and further demonstrated by the first total synthesis of cis-crotonin.     

A bifunctional rosin-derived thiourea catalyzed asymmetric tandem reaction and its new mechanism

A direct asymmetric tandem reaction of a-nitro ketones with b g-unsaturated a-ketoesters was found to be catalyzed by a bifunctional rosin-derived thiourea and gave 5-nitro-2-actoxyl-2-pentenates in excellent ee values and yields,a much better result than previously reported.Furthermore,through theoretical analysis,literature research and experimental verifications,a new mechanism involving an inverse-electron-demand Diels–Alder(IEDDAR) and a retro-Henry reaction was proposed.