Solvent effects on Diels-Alder reaction in ionic liquids:A reaction density functional study

Extensive experimental studies have been performed on the Diels-Alder(DA)reactions in ionic liquids(ILs),which demonstrate that the IL environment can significantly influence the reaction rates and selectivity.However,the underlying microscopic mechanism remains ambiguous.In this work,the multiscale reaction density functional theory is applied to explore the effect of 1-butyl-3-methylimidazolium hexafluorophosphate([BMIM][PF_(6)])solvent on the reaction of cyclopentadiene(CP)with acrolein,methyl acrylate,or acrylonitrile.By analyzing the free energy landscape during the reaction,it is found that the polarization effect has a relatively small influence,while the solvation effect makes both the activation free energy and reaction free energy decrease.In addition,the rearrangement of local solvent structure shows that the cation spatial distribution responds more evidently to the reaction than the anion,and this indicates that the cation plays a dominant role in the solvation effect and so as to affect the reaction rates and selectivity of the DA reactions.

An Enantioselective Approach to Heteroatom-Containing Bicyclic Derivatives via Inverse-Electron-Demand Diels-Alder Reactions

Chiral heteroatom-containing bicyclic scaffolds are important pharmacophores and prevalent in bioactive natural products and drug molecules.Herein,we report a unified approach for the divergent synthesis of chiral heteroatom-containing bicyclic derivatives by lanthanide(lil)-catalyzed asymmetric inverse-electron-demand Diels-Alder reactions of 2-pyrones.These reactions occur with vari-ous readily available dihydropyrroles and dihydrofurans as dienophiles,providing a step-economical synthetic platform for densely functionalized ciss-hydroindoles and cis-hydrobenzofurans with excellent yields and enantioselectivities.The synthetic utility of this approach is demonstrated by the concise synthesis of(-)-α-lycorane and(-)-lycorine alkaloids.

Furans-Maleimides Diels-Alder Reactions in Protic Ionic Liquid

The authors have studied the Diels-Alder reactions between furan derivatives and maleimide derivatives in an ionic liquid and have found that higher reactivity can be obtained in a protic ionic liquid [Mim]Tf2N than in the conventional organic solvent. Furthermore, in the Diels-Alder reactions of 2- and 2,5-alkylfurans with N-alkylma- leimide, the reactivity increases by extending the alkyl chain length of N-alkylmaleimide. In addition, it was demon- strated that endo-selectivity increases when 2,5-disubstituted furans are used. These results will be explained by comparing the stability of the Diels-Alder adduct with that of the products obtained from the reactions of 2-substituted furans and 2,5-disubstituted furans.

Synthesis of Novel Bisoxazoline Ligands for the Enantioselective Diels-Alder Reaction

Four novel bisoxazoline ligands 8a-d were synthesized from （S）-amino alcohols and could be formed effective catalysts （up to 77% ee for endo isomer） with Cu（OTf）2 for enantioselective Diels-Alder addition. The facility of the reaction was dependent on the nature of the substituent R in the bisoxazoline ligand.

Diels-Alder Reaction of Hedychenone and Maleic Anhydride

Diels-Alder reaction of hedychenone 1 and maleic anhydride 2 gave several products 4 similar to 7, whose structures were identified by spectral methods. Effect of temperature on the reaction was disscussed.

Crystal Structure of Derivative of H_4′-NOBIN and the Applications in Hetero-Diels-Alder Reaction

Novel Schiff bases of H4＇-NOBIN 5a and 5b were synthesized by condensation of 3 with aldehydes. Compound 5b was structurally characterized by single-crystal X-ray diffraction. The asymmetric hetero-Diels-Alder reactions were carried out with high yields and good enantioselectivities in the presence of Ti-（S）-5a complex as catalyst. Crystallographic data for 5b： C27H22BrNO, Mr = 456.37, triclinic, space group P1 with a = 9.1618（2）, b = 10.3836（2）, c = 12.7718（2） А,α=105.4860（10）,β= 94.6360（10）, γ= 108.4610（10）°, V= 1092.32（4）А^3, Z=2, Dc= 1.388 g/cm^3, μ= 1.900 mm^-1, F（000） = 468, R = 0.0476 and wR = 0.1248 for 3092 observed reflections （I〉 2σ（I））.

Diels-Alder Reactions of 3-Carboethoxy- and 3-Carbonitrile-2-Cyclohexen-1-one

Aluminum chloride induced Diels-Alder reactions of 3-carboethoxy- and 3-carbonitrile-2-cyclohexen-1-one with cyclopentadiene, isoprene and (E)-piperylene were described. Thestereochemistry of the adducts were confirmed by 2D-NMR spectroscopy and isomerizationreactions.

Mannich-Type Reactions of Aldimines and Hetero Diels-Alder Reactions of Aldehydes Catalyzed by Anion-Type Lewis Bases Derived from a Single Molecule

Mannich-type reactions of aldimines with silyl enolates and hetero Diels-Alder reactions of aldehydes with Danishef-sky’s diene in the presence of anion catalysts derived from proline were performed to afford the corresponding products in high yields.

SYNTHESIS OF POLYSUBSTITUTED AROMATIC COMPOUNDS:Ⅰ.THE DIELS-ALDER REACTION OF SELENO SUBSTITUTED 3-SULFOLENES WITH DIMETHYL ACETYLENEDICARBOXYLATE

The seleno substituted aromatic compounds were prepared via the Diels-Alder reaction of seleno substituted 3-sulfolenes with dimethyl acetylenedicarboxylate followed by DDQ dehydrogenation.

Asymmetric Diels-Alder Reaction of 1-(S_R)-p-Tolylsulfinyl-3-penten-2-one with Cyclopentadiene Catalzed by a Chiral Titanium Reagent

Double asymmetric Diels-Alder reaction of 1(SR)-p-Tolylsulfinyl-3-penten-2-one with cyclopentadiene using a chiral titanium reagent was performed. The diastereoselectivity dependent on the size of aryl substituent involved in the chiral ligands was discussed Absolute configuration of the cycloadducts was conformed. Dramatic reversal of selectivity is observed.

Studies on the Total Synthesis of Hainanolide(Ⅲ)-Unusual Diene Isomerization in a Diels-Alder Reaction

An unexpected diene isomerization of the triene acid 3 in the Lewis acid catalyzed intramolecular Diels-Alder reaction was observed

DIELS-ALDER REACTIONS OF FURAN WITH DIENOPHILES CATALYZED BY YbCl_3 Zi Niu ZHOU and Qi SHEN

The yield and stereoselectivity of the Diels-Alder reactions between furan(or 2-methylfuran)and different dienophiles are markedly enhanced by the catalysis of anhydrous YbCl_3.

Aqueous Diels-Alder Reactions of Cyclopentadicnc with Symmetric Diester of Fumarate or Maleate

Symmetric, diesters of cis- or trans- bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylate were prepared by aqueous Diels-Alder reaction of cyclopentadiene with symmetric diester of fumarate or maleate.

A Novel Example of Hetero Diels-Alder Reaction

2, 3, 3a, 4, 5, 9b-hexahydro-8-(N-methylsulfamylmethyl)-4-phenylfuro[3, 2-c]quinoline was obtained when the alkylation of compound 1 was carried out with THF as solvent. The structure of the product was determined and the mechanism of the reaction was studied and proved by the imitation reaction.

Determination of ergocalciferol in human plasma after Diels-Alder derivatization by LC-MS/MS and its application to a bioequivalence study

An accurate, sensitive and selective method is developed for determination of ergoealeiferol （vitamin D2） in human plasma using LC-MS/MS. After liquid-liquid extraction with n-hexane, ergoealeiferol was derivatized by reacting with 4-phenyl-l,2,4-triazoline-3,5-dione （PTAD）, a strong dienophile based on Diels-Alder reaction. Ergocalciferol and its deuterated internal standard, ergocalciferol-d6, were analyzed on X Select CSH Cls （100 mmx4.6 mm, 2.5 lam） column using acetonitrile and 0.1% （v/v） formic acid in water containing 0.14% methylamine within 6.0 min under gradient elution mode. Tandem mass spectrometry in positive ionization mode was used to quantify ergocalciferol by multiple reaction monitoring （MRM）. Entire data processing was done using Watson LIMSTM software which provided excellent data integrity and high throughput with improved operational efficiency. The major advantage of this method includes higher sensitivity （0.10 ng/mL）, superior extraction efficiency （〉83%） and small sample volume （100 ~tL） for processing. The method was linear in the concentration range of 0.10-100 ng/mL for ergoealciferol. The intra-batch and inter-batch accuracy and precision （% CV） values varied from 97.3% to 109.0% and 1.01% to 5.16%, respectively. The method was successfully applied to support a bioequivalence study of 1.25 mg ergoealciferol capsules in 12 healthy subjects.

Assessment on facile Diels-Alder approach of α-pyrone and terpenoquinone for the expedient synthesis of various natural scaffolds

The development of highly facile synthetic procedures for the expedient synthesis of complex natural molecules is always in demand.As this aspect,the Diels-Alder reaction(DAR)has a versatile approach to the synthesis of complex natural compounds and highly regio-/stereoselcetive heterocyclic scaffolds.Additionally,α-pyrone and terpeno-quinone are two versatile key intermediates that are prevalent in various bioactive natural compounds for instance,(±)-crinine,(±)-joubertinamine,(±)-pancratistatin,(−)-cyclozonarone,and 8-ephipuupehedione,etc.Hence,the current review summarizes the Diels-Alder reaction application ofα-pyrone and terpenoquinone to the construc-tive synthesis of various natural products over the past two decades(2001-2021).Equally,it serves as a stencil for the invention and development of new synthetic strategies for high-complex molecular structured natural and heterocy-clic molecules.

Total Synthesis of UCS1025A via Tandem Carbonylative Stille Cross Coupling and Diels-Alder Reactiont

We report an efficient and convergent strategy for the total synthesis of UCS1025A and its diastereomer tetra-epi-UCS1025A.Ucs1025A is a representative member of the naturally occurring pyrrolizidinone polyketides,from which members with potent antibacterial,antifungal,and anticancer activities have been identified.Our approach features a tandem carbonylative Stille cross coupling and Diels-Alder reaction to forge a key C-C bond and build the trans-decalin system.This tandem process utilizes carbon monoxide as a one-carbon linchpin to stitch a vinyl triflate and a vinylstannane together and form the desired enone moiety for the subsequent intramolecular Diels-Alder cyclization.Our synthesis also provides a versatile approach for the synthesis of other related pyrrolizidinone-containing polyketides.

Sustainable synthesis of high-density fuel via catalytic cascade cycloaddition reaction

The access to high-density hydrocarbon fuels from biomass for the reduction of dependence on fossil resources has been a research highlight in recent years. It is well known that cycloalkanes are the components of fuels with higher energy density than straight or branched alkanes. Herein, we developed a new catalytic pattern to synthesize dimethyltetradecahydroanthracenes(DMTHA), a kind of tricyclic alkane, from biomass-derived isoprene and p-benzoquinone via a cascade Diels-Alder reaction followed by a hydrodeoxygenation reaction. Vanadium supported on titanium dioxide(V-TiO_(2)) was applied to catalyze the cascade Diels-Alder reaction and it was disclosed that V with appropriate V^(4+)/V^(5+) ratio on the surface of TiO_(2) could activate quinones. Experimental tests showed that the heating value of final products was up to 45.7 MJ/kg. The development of new high-density fuel molecules is a long-term trend for the future renewable and sustainable fuel energy application.

Research Progress of Tung Oil/UV Photocomposite Curing Material

Tung oil(TO)/ultraviolet(UV)photo-composite curing material possesses the characteristics of low curing temperature,low material shrinkage and low environmental pollution.Accordingly,this material must be developed and utilized with the conjugated double bonds contained in the long chain of the main structure(α-tung acid)molecules in the refined TO.The aforementioned material can be chemically modified using a variety of chemical methods to develop a new TO-based UV photocurable material due to its unique chemical properties.This work reviews the research progress of TO/UV photo-composite curing materials in recent years.Firstly,the chemical structure and application of TO and UV Photocatalysis Technology were briefly introduced.Secondly,the research status of novel TO/UV photo-composite curing materials developed by the Diels-Alder reaction was discussed.The method and curing effect of the UVcuring system constructed by other chemically modified TO were also discussed.Thereafter,the application of TO in industrial production is introduced from four directions:the application of TO in biodiesel,the application in synthetic resin,the application in self-healing coating and microcapsules and other applications.Finally,the research and application prospects of TO/UV photo-composite curing materials were presented.