An efficient synthesis of pyrano [4,5-c] pyrrole derivatives through microwave—accelerated intramolecular Knoevenagal hetero Diels–Alder reaction

Synthesis of novel pyranopyrrole derivatives has been achieved by a one-pot IMHDA reaction of N-substituted aldehydes with various diones in the presence of ethylene diaminediacetate (EDDA) in excellent yields under mild conditions.     

Two polycyclic compounds derived from a Diels–Alder reaction

In both 9,10‐di­methoxy‐11‐oxatri­cyclo­[6.2.1.0^2,7]­undeca‐4,9‐diene‐3,6‐diol, C₁₂H₁₆O₅, (I), and 5,6‐di­methoxy‐3,7‐dioxa­tetra­cyclo­[6.4.0.0^2,6.0^4,12]­dodec‐9‐en‐11‐ol, C₁₂H₁₆O₅, (II), the hetero‐oxygen‐containing five‐membered rings have an envelope conformation. The six‐membered rings are in a boat conformation in compound (I), and in (II), one is in a half‐boat and the other is in a slightly distorted boat conformation. The mol­ecules in both compounds interact through classical hydrogen bonds and C—H?O contacts.     

Recent Progress in Dehydro(genative) Diels–Alder Reaction

In recent years, remarkable progress has been made in dehydro or dehydrogenative Diels–Alder (D–A) reactions. This Minireview gives an overview of the major two strategies for dehydro(genative) Diels–Alder reactions, which differ in dehydrogenation and D–A cyclization sequence. Reactions in which D–A cycloaddition is followed by dehydrogenation are useful methods for the synthesis of various aromatic compounds, whereas advancements in dehydro genative procedures with oxidants or catalysts prior to D–A cycloaddition offer yet further new routes to functionalized cycloadducts. Recent leading findings are highlighted and the current state of the art, scope, and limitations of these processes are discussed in this Minireview.     

Arene Trifunctionalization with Highly Fused Ring Systems through a Domino Aryne Nucleophilic and Diels–Alder Cascade

A convenient and efficient domino aryne process was developed under transition‐metal‐free conditions to generate a range of tetra‐ and pentacyclic ring systems. This transformation was realized via a 1,2‐benzdiyne through a nucleophilic and Diels–Alder reaction cascade using styrene as the diene moiety. Three new chemical bonds, namely one C?N and two C?C bonds, and two benzofused rings could be constructed concomitantly, which was made possible by distinct chemoselective control at both the 1,2‐aryne and 2,3‐aryne stages. Moreover, in‐depth studies were carried out on the domino aryne precursors and controlling the diastereoselectivity.     

Practical highly enantioselective synthesis of propargylamines through a copper-catalyzed one-pot three-component condensation reaction

The one-pot three-component reaction of terminal alkynes, aldehydes and secondary amines in the presence of copper(I) bromide/quinap is reported. The reaction scope has been determined and a broad variety of all three components has been used, which afforded the corresponding propargylamines in good to excellent yields and moderate to very good enantioselectivities. The reaction showed a strong positive nonlinear effect. The transformation of a propargylamine intermediate into the alkaloid (S)-(+)-coniine has also been described.     

Multiarm star polymers with peripheral dendritic PMMA arms through Diels–Alder click reaction

Dendritic 2‐ and 4‐arm PMMA‐based star polymers with furan‐protected maleimide at their focal point, (PMMA)_2n‐MI and (PMMA)_4n‐MI were efficiently clicked with the peripheral anthracene functionalized multiarm star polymer, (α‐anthryl functionalized‐polystyrene)_m‐poly(divinyl benzene) ((α‐anthryl‐PS)_m‐polyDVB) through the Diels–Alder reaction resulting in corresponding multiarm star block copolymers: (PMMA)_2n‐(PS)_m‐polyDVB and (PMMA)_4n‐(PS)_m‐polyDVB, respectively. Molecular weights (M_w,TDGPC), hydrodynamic radius (R_h), and intrinsic viscosity (η) of the multiarm star polymers were determined using three‐detection GPC (TD‐GPC). The high efficiency of this methodology to obtain such sterically demanding macromolecular constructs was deduced using ¹H‐NMR and UV–vis spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Polymer grafting onto polyurethane backbone via Diels–Alder reaction

The aliphatic polyurethane with pendant anthracene moieties (PU‐anthracene) was prepared from polycondensation of anthracen‐9‐yl methyl 3‐hydroxy‐2‐(hydroxymethyl)‐2‐methylpropanoate (anthracene diol), 1 with hexamethylenediisocyanate in the presence of dibutyltindilaurate in CH₂Cl₂ at room temperature for 10 days. Thereafter, the PU‐anthracene (M_n,GPC = 12,900 g/mol, M_w/M_n = 1.87, relative to PS standards) was clicked with a linear α‐furan protected‐maleimide terminated‐poly(methyl methacrylate) (PMMA‐MI) (M_n,GPC = 2500 g/mol, M_w/M_n = 1.33), or ‐poly(ethylene glycol) (PEG‐MI) (M_n,GPC = 550 g/mol, M_w/M_n = 1.09), to result in well‐defined PU‐graft copolymers, PU‐g‐PMMA (M_n,GPC = 23800 g/mol, M_w/M_n = 1.65, relative to PS standards) or PU‐g‐PEG (M_n,GPC = 11,600 g/mol, M_w/M_n = 1.45, relative to PS standards) using Diels–Alder reaction in dioxane/toluene at 105 °C. The Diels–Alder grafting efficiencies were found to be over 93–99% using UV spectroscopy. Moreover, the structural analyses and the thermal transitions of all copolymers were determined via ¹H NMR and DSC, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 521–527     

Graft copolymers via ROMP and Diels–Alder click reaction strategy

Anthracene‐functionalized oxanorbornene monomer and oxanorbornenyl polystyrene (PS) with ω‐anthracene end‐functionalized macromonomer were first polymerized via ring‐opening metathesis polymerization using the first‐generation Grubbs' catalyst in dichloromethane at room temperature and then clicked with maleimide end‐functionalized polymers, poly(ethylene glycol) (PEG)‐MI, poly(methyl methacrylate) (PMMA)‐MI, and poly(tert‐butyl acrylate) (PtBA)‐MI in a Diels–Alder reaction in toluene at 120 °C to create corresponding graft copolymers, poly(oxanorbornene)‐g‐PEG, poly(oxanorbornene)‐g‐PMMA, and graft block copolymers, poly(oxanorbornene)‐g‐(PS‐b‐PEG), poly(oxanorbornene)‐g‐(PS‐b‐PMMA), and poly(oxanorbornene)‐g‐(PS‐b‐PtBA), respectively. Diels–Alder click reaction efficiency for graft copolymerization was monitored by UV–vis spectroscopy. The dn/dc values of graft copolymers and graft block copolymers were experimentally obtained using a triple detection gel permeation chromatography and subsequently introduced to the software so as to give molecular weights, intrinsic viscosity ([η]) and hydrodynamic radius (R_h) values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A facile one-pot three-component synthesis of ferrocene-grafted dispiro pyrrolidine/pyrrolizidine scaffolds through intermolecular [3+2] cycloaddition reaction of ferrocenyl Baylis-Hillman adduct

A one-pot synthesis of ferrocene-grafted dispiropyrrolidine/pyrrolizidine scaffolds has been accomplished in good yields through a facile 1,3-dipolar cycloaddition of various azomethine ylides derived from diketones and secondary amino acids with Baylis-Hillman adduct derived from ferrocene carbaldehyde. The regiochemical and stereochemical outcomes of the cycloaddition reaction were ascertained by X-ray crystallographic studies of one of the cycloadducts.     

Highly stereoselective one-pot synthesis of tetrasubstituted alkenes via carbopalladation reaction of fluorine-containing acetylene derivatives

Treatment of fluoroalkylated alkynes with various aryl halides and arylboronic acids in the presence of Pd(0) in DMF/H₂O at 100 °C for 2 h led to the smooth three-component coupling reaction, the corresponding tetrasubstituted alkenes being obtained in high yields stereoselectively.     

Highly efficient one-pot,three-component synthesis of 1, 5-benzodiazepine derivatives

A general, mild and efficient protocol for the synthesis of ethyl 4-methyl-2-（thiophen）-2,5-dihydro-1,5- benzodiazepine-3-carboxylate is achieved for first time using H3PMo12O40 in ethanol at 0 ℃ by a one- pot, three-component condensation of various thiophene aldehydes, substituted o-phenylenediamines and ethyl acetoacetate. Compared with the conventional synthesis method, this procedure has the advantages of convenient operation, excellent yields, and environmentally benign. A plausible formation mechanism has been proposed. The structure of the products is characterized by1H NMR, IR, MS and elemental analysis.     

Thermally reversible crosslinking of polystyrene via the furan–maleimide Diels–Alder reaction

Mixtures of maleimidomethylated polystyrene with difurfuryl adipate or with furfuryl alcohol-esterified poly[styrene-co-(maleic anhydride)] underwent thermally reversible Diels–Alder crosslinking. Reversal of crosslinking occurred rapidly at 150°C. The instability of the furfuryl group, however, limits the practicability of the reaction. © 1992 John Wiley & Sons, Inc.     

Fourfold Diels–Alder Reaction of Tetraethynylsilane

A series of ethynylated silanes, including tetraethynylsilane, was treated with tetraphenylcyclopentadienone at 300 °C under microwave irradiation to give the aromatized Diels–Alder adducts as sterically encumbered mini‐dendrimers with up to 20 benzene rings. The sterically most congested adducts display red‐shifted emission through intramolecular π–π interactions in the excited state.     

Highly diastereoselective synthesis of new indolopyrroloquinolines through intramolecular imino Diels-Alder reactions

A new, efficient and highly diastereoselective one-pot synthesis of cis-fused indolopyrroloquinoline derivatives is described through imino Diels-Alder reaction of substituted anilines or naphthylamines with N-prenylated-2-formyl-3-chloroindoles catalyzed by La(OTf)₃.     

Regio and diastereoselective synthesis of functionalized 2,3-dihydrofuro[3,2-c]coumarins via a one-pot three-component reaction

An efficient and straightforward synthesis of furo[3,2-c]coumarins via the one-pot three-component condensation of aromatic aldehydes, 4-hydroxycoumarin and α-chloroketones in refluxing n-propanol is described. Pyridine or a mixture of AcOH and AcONH₄ was used as a basic catalyst.     

A novel microwave-mediated one-pot synthesis of indolizines via a three-component reaction

[reaction: see text] The microwave-mediated three-component reaction of acyl bromide, pyridine, and acetylene is catalyzed by basic alumina to give corresponding indolizines in excellent yields in a one-pot reaction.     

Novel one-pot expeditious synthesis of 2,4-disubstituted thiazoles through a three-component reaction under solvent free conditions

An expeditious one pot method has been developed for the synthesis of 2,4-disubstituted thiazoles under solvent free conditions via a multicomponent approach. Substituted thiazoles were synthesized with high yields by the reaction of cyclic ketones, thiosemicarbazide, and phenacyl bromides or 3-(2-bromoacetyl)-2H-chromen-2-ones in a shorter reaction time with high purity via simple purification technique.