Convenient synthesis of spiro[indoline-3,4'-pyrano[2,3-c]pyrazole] and spiro[acenaphthyl-3,4'-pyrano[2,3-c]pyrazoles] via fourcomponent reaction

The base promoted four-component reaction of hydrated hydrazine, dimethyl acetylenedicarboxylate, isatines and malononitrile (ethyl cycanoacetate) in ethanol afforded polysubstituted spiro[indoline-3,4‘-pyrano[2,3-c]pyrazoles] and spiro[acenaphthyl-3,4-pyrano[2,3-c]pyrazoles]     

1,3-Dipolar cycloaddition for selective synthesis of functionalized spiro[indoline-3,3'-pyrrolizines]

The 1,3-dipolar cycloaddition reaction of dimethyl hex-2-en-4-ynedioate with azomethine ylides derived from reaction of L-proline with various isatins in methanol selectively resulted in the formation of functionalized spiro[indoline-3,3'-pyrrolizine]acrylates as main products and spiro[indoline-3,3'-pyrrolizine]propiolates as minor products.This result indicated that the electron-deficient alkyne has higher reactivity than that of electron-deficient alkene in 1,3-dipolar cycloaddition reaction.     

Synthesis of new pyrido[3,4-c]carbazole derivatives

Previously unknown 2-[6-hydroxy-9-(4-methoxyphenyl)-1,2,3,9-tetrahydro-4H-carbazol-4-ylidene]malononitrile was synthesized by the Nenitzescu reaction and was used for the construction of new tetracyclic compounds, viz., pyrido[3,4-c]carbazoles. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1600–1604, September, 2006.     

Efficient one-pot synthesis of spiro[indoline-3,4′-pyrazolo[3,4-e][1,4]thiazepine]dione via three-component reaction

An efficient one-pot synthesis of spiro[indoline-3,4′-pyrazolo[3,4-e][1,4]thiazepine] dione derivatives via three-component reaction of 5-amino-3-methylpyrazole, isatin, and thioacid is described. This new protocol produces novel heptacyclic spirooxindole derivatives in good yields in comparison to conventional pentacyclic compounds. This method proceeds through a 3-(5-aminopyrazol-3-yl)-3-hydroxy-2-oxindoline intermediate (Baylis-Hillman type adduct), unlike 3-indolylimine (the intermediate like Shiff-Bases) as in conventional methods. The structure of one representative compound has been confirmed by X-ray diffraction analysis.     

A facile one-pot regioselective synthesis of functionalized novel benzo[f]chromeno[4,3-b][1,7]naphthyridines and benzo[f][1,7]naphthyridines via an imino Diels-Alder reaction

A novel series of functionalized 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and 1,3-diphenylbenzo[f][1,7]naphthyridines have been synthesized by an efficient regioselective one-pot multicomponent synthesis through intra and intermolecular imino Diels-Alder reaction. In this method, we have achieved complete regioselectivity and atom economy with polysubstituted core motifs in moderate to good yields. The proposed mechanism of this reaction has also discussed.     

Diastereo- and regioselectivity in Diels-Alder reaction of [1,4,2]diazaphospholo[4,5-a]pyridines

[1,4,2]Diazaphospholo[4,5-a]pyridines undergo diastereoselective Diels-Alder reaction at the >CP- functionality with 2,3-dimethylbutadiene and isoprene in the presence of sulfur or selenium. The reaction with isoprene occurs regioselectively. On carrying out the reaction with diene in presence of methyl iodide, the initially formed [2+4] cycloadduct is methylated regioselectively at the σ²,λ³-nitrogen. The results of the DFT calculations of the Diels-Alder reaction with isoprene are in accord with the observed regioselectivity. The relative stabilities of the two transition structures have been explained on the basis of NBO analysis.     

The One-Pot Synthesis and Diels-Alder Reactivity of 2,5-Dihydrothiophene- 1,1-dioxide-3-carboxylic Acid

Abstract

A one-pot preparation of 2,5-dihydrothiophene-1,1-dioxide-3-carboxylic acid (3-sulfolene-3-carboxylic acid) is reported. The carboxylation of 3-sulfolene, exclusively at the 3-position, using CO₂ and DBU proceeds to >90% conversion. A rapid workup gives 3-sulfolene-3-carboxylic acid, a stable precursor to 1,3-butadiene-2-carboxylic acid. High conversions to Diels-Alder adducts were obtained upon treatment of 3-sulfolene-3-carboxylic acid with various dienophiles.     

Efficient one-pot catalyst-free synthesis of novel coumarin- spiro[indoline-3,4'-pyran] conjugates via three-component domino reaction in aqueous medium

A simple, efficient, eco-friendly and catalyst-free procedure was developed for the construction of novel coumarin-spiro[indoline-3,4'-pyran] conjugates via three-component reactions of various synthetic beta-ketoesters with isatins and malononitrile in aqueous medium. In addition to operational simplicity and absence of tedious separation procedures, being catalyst–free is the prominent advantage of this method.     

One pot four-component reaction for the efficient synthesis of spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-3′-carboxylate derivatives

A novel one pot protocol has been developed to synthesize various spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-3′-carboxylate derivatives from the four-component reaction of isatin, malononitrile, hydrazine derivatives and dialkyl acetylenedicarboxylates. In this process two C–C bonds, two C–N bonds and one C–O bond have formed in one pot. The notable features of this protocol are simple and environmentally benign reaction condition, easy isolation of products, applicable to a wide range of readily available starting materials and good yields.     

Construction of 9-functionalized xanthenes via Diels-Alder reaction of stable ortho-quinone methides and arynes

Diels-Alder reaction of stable o–quinone methides and arynes has been developed, providing 9–aryl and 9–cinnamyl substituted xanthenes in moderate to high yields.     

Lewis acid catalyzed Povarov reaction of pentafulvenes and spiro[2,4]-hepta-[4,6]-diene: An efficient access to cyclopentene fused quinolines

An efficient protocol for the Lewis acid catalyzed three-component aza-Diels-Alder reaction of pentafulvenes as dienophile has been developed. Cyclopentene fused tetrahydroquinolines were formed in good yields with excellent diastereoselectivities. The method was extended to spiro[2,4]hepta-4,6-diene, by which 3,4-dihydroquinoline derivatives were obtained. The aromatization of cycloadducts furnished corresponding quinoline derivatives.     

[60]Fullerene adducts with 9-substituted anthracenes: mechanochemical preparation and retro Diels-Alder reaction

Three 9-substituted anthracene derivatives, that is, 9-hydroxymethylanthracene (2), 9-methoxymethylanthracene (3) and bis(9-anthrylmethyl) adipate (6), were chosen as the model compounds to evaluate the reactivity in their Diels-Alder reactions with [60]fullerene and in retro Diels-Alder reactions of the formed cycloadducts. Corresponding adducts 4, 5 and 7 were prepared in high yields under solvent-free conditions using high-speed vibration milling technique. In order to determine thermal stabilities of adducts 4, 5 and 7, their dissociations in the temperature range of 40-65 °C were investigated. Fitting the dissociation rates and temperatures to the Arrhenius equation gives the activation energies of 25.8, 21.8 and 24.9 kcal/mol for compounds 4, 5 and 7, respectively.     

Fully regio- and endo-stereoselective synthesis of new polycyclic allylic sulfides via a Diels-Alder reaction. Synthetically useful transformations of these sulfides

Thermal and Lewis acid catalyzed cycloadditions of (Z)-1,2-diheterosubstituted-1,3-dienes to a variety of dienophiles are described. Both endo/exo and regioselectivity have been investigated. In all cases cycloaddition reactions exhibited full regio- and endo-stereoselectivity. The obtained cycloadducts are new polycyclic allylic sulfides carrying much structural and stereochemical informations. Work on transformation of the adducts, mainly to the corresponding new 1,3-dienes and aromatic compounds, is also presented.     

Condensation reaction of 3,4-dibenzoyl-1-methyl-2,5-diphenylpyrrole and -1-phenylpyrazole with methylamine derivatives affording pyrrolo [3,4-c]pyridine and 2H-pyrazolo[3,4-c]- and [4,3-c]pyridines

The reaction of 3,4-dibenzoyl-1-methyl-2,5-diphenylpyrrole ( 1 ) and -1-phenylpyrazole ( 2 ) with methylamines ( 3a-c ) afforded pyrrolo[3,4-c]pyridine ( 4 ), and isomeric 2H-pyrazolo[3,4-c]pyridines ( 5a-c ) and [4,3-c]pyridines ( 6a-c ), respectively.     

Novel phosphonated bicyclic frameworks from Diels-Alder reaction as chelating agents of di- and trivalent metal cations

The synthesis of novel [4+2] cycloadducts by Diels-Alder (DA) reaction between diethyl 1-phosphono-1,3-butadiene and cyclic CC and NN dienophiles, such as maleimide and 1,2,4-triazole-3,5-dione derivatives, is described. These phosphonated bicyclic frameworks feature a cage shape enabling metal chelation. Indeed, stable complexes were formed in solution with M²⁺ and M³⁺ metal cations, as evidenced by HRMS in the ESI mode (electrospray ionization). L₁:M (one ligand-one metal) and L₂:M (two ligands-one metal) complexes were identified depending on the nature of the cation.     

Oxidative dearomatization and retro-Diels-Alder/Diels-Alder cascade: Synthesis and photoreactions of azepane annulated bicyclo[2.2.2]octenone

Synthesis of azepane annulated bicyclo[2.2.2]octenone via oxidative dearomatization and intramolecular π⁴s?+?π²s cycloaddition has been described. Manipulation of the adduct led to tricyclic compounds having a β,γ-enone chromophore whose photoreaction upon triplet and singlet excitation furnished polycyclic systems having azepane ring systems.     

2,5-diphenyl-3,4-bis[p-(phenylethynyl)phenyl]cyclopentadienone and product of its Diels-Alder homocondensation

A new monomer of the ABA type, 2,5-diphenyl-3,4-bis[p-(phenylethynyl)phenyl]-cyclopentadienone, was synthesized. The Diels-Alder homocondensation of the monomer resulted in a highly branched polyphenylene (M _w=160000), readily soluble in organic solvents. The polymer obtained is thermally stable up to 600 °C (in argon atmosphere) and has a glass transition of 280°C. The structure of the monomer and polymer was confirmed by¹H NMR,¹³C NMR, IR Fourier, and Raman Fourier spectroscopy. Max-Planck-Institut für Polymerforschung, Ackermann-Weg, 10, Mainz, Deutschland. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 953–958, May, 1999.     

Selective construction of indeno[1,2-b]phenothiazine and indeno[2,1-c]phenothiazine via tandem annulation reaction

AcOH promoted annulation reaction of 2-arylideneindane-1,3-diones with methyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetate in refluxing ethanol afforded pentacyclic tetrahydroindeno [1,2-b]phenothiazine in satisfactory yields and with high diastereoselectivity according to the unexpected tandem annulation process. When the above reaction was carried out in refluxing acetic acid, isomeric dihydroindeno [1,2-b]phenothiazines and dihydroindeno [2,1-c]phenothiazines were obtained in comparable yields according to alternate tandem annulation process.     

Tandem Approach to Functionalized Pyrrolo[3,4-α]carbazole-1,3-diones via a Pd-catalyzed Indole-to-carbazole Transformation

A one-pot and efficient tliree-component reaction of indoles, acrylates and maleimides for the synthesis of pyrrolo[3,4-α]carbazole-1,3-dione derivatives was developed. Three C-C bonds and one ring were created in a single step via an indole-to-carbazole transformation triggered by Pd(II)-catalyzed direct C3-alkenylation of indoles.     

Tandem furo[3,4-b]pyridine formation—Diels-Alder reaction: an approach to the synthesis of nitrogen containing heterocyclic analogues of 1-arylnaphthalene lignans

The coupling of Fischer carbene complexes with 2-alkynyl-3-pyridine carbonyl derivatives has been examined. The reaction affords furo[3,4-b]pyridine as transient intermediates; the latter undergo [4+2] cycloaddition with an electron-deficient dienophile. Acid/base-induced ring opening of the exo-cycloadducts followed by aromatization give substituted quinolines related to heterocyclic analogues of 1-arylnaphthalene lignans. An intramolecular variant of this protocol is also feasible with use of unactivated alkenyl tethers; however, the bridged cycloadducts are unisolable as they undergo spontaneous ring opening to yield alcohol. This method is also useful for the in situ generation of the furo[3,4-b]quinoline intermediate for the first time, which can be trapped with dienophiles.