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Heterocyclization Reactions (heterocyclization + reaction)
Selected AbstractsHeterocyclization Reactions of 2-(2-Propynylthio)-4(1H)-quinazolinone Derivatives when Treated with Electrophilic and Nucleophilic Reagents.CHEMINFORM, Issue 18 2004Yu. L. Zborovskii No abstract is available for this article. [source] ChemInform Abstract: The Reactivity of N-Tosylphenylaziridine versus N-Tosylphenylazetidine in Heterocyclization Reactions.CHEMINFORM, Issue 5 2002Ioana Ungureanu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Copper-Catalyzed Preparation of ,-Alkylidenebutenolides and Isocoumarins under Mild Palladium-Free ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009Samuel Inack-Ngi Abstract A general and efficient copper(I)-catalyzed cross-coupling and heterocyclization reaction of terminal alkynes and ,-iodo-,,,-unsaturated acid derivatives has been developed under very mild conditions. This method provides easy access from good to excellent yields of a variety of 5-ylidenebutenolides and 3-substituted isocoumarins with excellent regio- and stereoselectivity. This procedure does not require the use of any expensive supplementary additives, and is palladium-free. [source] [8+2] and [8+3] Cyclization Reactions of Alkenyl Carbenes and 8-Azaheptafulvenes: Direct Access to Tetrahydro-1-azaazulene and Cyclohepta[b]pyridinone DerivativesCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2008José Barluenga Prof. Abstract The reactivity of Fischer alkenyl carbenes toward 8-azaheptafulvenes is examined. Alkenyl carbenes react with 8-azaheptafulvenes with complete regio- and stereoselectivity through formal [8+3] and [8+2] heterocyclization reactions, which show an unprecedented dependence on the C, substituent at the alkenyl carbene complex. Thus, the formal [8+3] heterocyclization reaction is completely favored in carbene complexes that bear a coordinating moiety to give tetrahydrocyclohepta[b]pyridin-2-ones. Otherwise, alkenyl carbenes that lack appropriate coordinating groups undergo a formal [8+2] cyclization with 8-azaheptafulvenes to give compounds that bear a tetrahydroazaazulene structure. A likely mechanism for these reactions would follow well-established models and would involve a 1,4-addition/cyclization in the case of the [8+2] cyclization or a 1,2-addition/[1,2] shift,metal-promoted cyclization for the [8+3] reaction. The presence of a coordinating moiety in the carbene would favor the [1,2] metal shift through transition-state stabilization to lead to the [8+3] product. All these processes provide an entry into the tetrahydroazaazulene and cycloheptapyridone frameworks present in the structure of biologically active molecules. Se ha estudiado la reactividad de alquenilcarbenos de Fischer con 8-azaheptafulvenos. Los alquenilcarbenos reaccionan con 8-azaheptafulvenos a través de reacciones de heterociclación formales [8+3] y [8+2] con completa regioselectividad y estereoselectividad, mostrando una dependencia del sustituyente C, del complejo alquenilcarbeno sin precedentes. Así, en los complejos carbeno que contienen un resto coordinante la reacción de heterociclación formal [8+3] se favorece completamente para dar tetrahidrociclohepta[b]piridin-2-onas. Por otra parte, los alquenilcarbenos que carecen de grupos coordinantes apropiados, experimentan una ciclación formal [8+2] con los 8-azaheptafulvenos para dar compuestos con estructura de tetrahidroazuleno. Un mecanismo probable para estas reacciones se fundamenta en modelos bien establecidos e implica una adición 1,4/ciclación en el caso de la ciclación [8+2] o una adición 1,2/ciclación promovida por una migración 1,2 del metal en el caso de la reacción [8+3]. La presencia de un resto coordinante en el carbeno favorece la migración 1,2 del metal a través de una estabilización del estado de transición, conduciendo al producto [8+3]. Todos estos procesos representan una vía de acceso a los esqueletos de tetrahidroazuleno y cicloheptapiridona presentes en la estructura de moléculas biológicamente activas. [source] Synthesis of Polyfunctionally Substituted Fused Pyrimidine Derivatives as Antimicrobial AgentsCHINESE JOURNAL OF CHEMISTRY, Issue 8 2008Abd EI-Monem Mohamed Farag EISSA Abstract A variety of pyrimidine derivatives 2,4 and annulated pyrimidine derivatives 5,17 have been synthesized via a sequence of heterocyclization reaction of readily available 6-naphthyl-4-oxo-2-thioxo-1,2,3,4-tetrahydroprimidine-5-carbonitrile (1) with different acidic and basic reagents. The new compounds were synthesized with the aim of study of their antimicrobial activity. The structures of all synthesized compounds were elucidated by elemental analysis and spectroscopic studies. [source] Efficient Routes to Acenaphthylene-Fused Polycyclic Arenes/Heteroarenes and Heterocyclic Fluoranthene AnaloguesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2005Kausik Panda Abstract The acenaphthenone-derived , -oxoketene dithioacetal 2 has been subjected to various [3 + 3] aromatic and heteroaromatic annulation and other heterocyclization reactions previously developed in our laboratory, providing short and efficient routes to a diverse range of known and unknown acenaphtho-annulated linear and angular PAHs, heteroaromatics and five-membered heterocycles in good yields. Thus, benzo- and naphthoannulation of 2 with various allyl and benzyl Grignard reagents afforded substituted fluoranthenes 4a,c and benzo[k]fluoranthene 8, respectively, in good yields. Similarly, the parent benzo[j]fluoranthene 15a and its substituted derivative 16b have been synthesized by base-induced conjugate 1,4-addition of arylacetonitriles to 2, followed by acid-induced cyclization of the conjugate adducts 12a,b to give 13a,b and subsequent further transformations. The adducts obtained by 1,4-addition of anions derived from acetophenone and acenaphthenone were subjected toheterocyclization in the presence of ammonium acetate to give 8-arylacenaphtho[1,2- b]pyridines 18a,b and bis(acenaphtho)-annulated pyridine 20. Heterocyclization of 2 with bifunctional nucleophiles such as 2-picolyllithium and guanidinium nitrate afforded the corresponding acenaphtho[1,2- b]quinolizinium salt 23 and acenaphtho[1,2- d]pyrimidine 24, respectively, in high yields. Finally, acenaphtho[1,2- c]-fused five-membered heterocycles such as 7-(methylthio)acenaphtho[1,2- c]thiophene (25), 7-(methylthio)acenaphtho[1,2- c]furan (27) and 7-(methylthio)acenaphtho[1,2- c]pyrrole-2-carboxylic acid (30) were obtained in good yields by subjection of 2 to Simmons,Smith reaction conditions or by treatment with dimethylsulfonium methylide or glycinate dianion. Some of these newly synthesized PAHs or fused heterocycles were subjected to Raney Ni desulfurization to furnish sulfur-free compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Facile and one pot synthetic routes for various novel, differently fused and promising heteropolycyclesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2010Shallu Gupta Four-component one pot cyclocondensation of aromatic aldehydes 1, ethyl cyanoacetate 2, barbituric acid 3 and ammonium acetate in methanol gave substituted and functionalised pyrido[2,3-d]pyrimidine derivatives 4 and 4, after initial Knoevenagel, subsequent Micheal and final heterocyclization reactions. Compounds 4 on reaction with different active methylene compounds resulted in the formation of again functionalized and diversly substituted pyrimidonaphthyridines 5-7, 9 and benzo[b] pyrimidonaphthyridines 8. The various compounds of systems 7 and 8 on further condensation with the reactive and mostly the bifunctional moieties like urea/thiourea, and 2-aminopyridine generated the novel and differently fused dipyrimidonaphthyridines 10/11 and pyrimidonaphthyridinoquinazolines 13/14, and pyridopyrimido- pyrimido[1,8]naphthyridines 15 and pyrimidonaphthyridino- pyridoquinazolines 16, respectively, hitherto unknown in literature. Compounds 7 on condensation with o -phenylenediamine produced novel pyrimidonaphthyridinobenzodiazepines 12. Other novel systems like pyrido[2,3-d;6,5-d,]dipyrimidines 17, dipyrimido[4,5-b:5,,4,-g][1,8]naphthyridines 18, 1,3,4,6,7,8,9,11-octazabenzo[de]naphthacenes 19, dipyrimido[4,5-b:5,,4,-g][1,8]naphthyridines 20, pyrimido[5,,4,:6,7][1,8]naphthyridino[4,3-b][1,5]benzodiazepines 21, dipyrimido[4,5-b:4,,5,-f][1,8]naphthyridines 22 and dipyrimido [4,5-b:5,,4,-g][1,8] naphthyridines 23 have also been generated in this study. J. Heterocyclic Chem., (2010). [source] Regioselective synthesis of pyrimido[5,4-c][2,1]benzothiazines by reactions of ,-chloroaldehydes with n-c-n binucleophilesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2010Kirill Popov The method of pyrimidine ring fusion at the [c] side of benzothiazines based on the reaction of their chloroaldehyde derivatives with amidines is described. Formation of the structural isomers of reaction products was investigated, and regioselectivity of heterocyclization reactions was shown. A number of novel pyrimidobenzothiazines were synthesized. J. Heterocyclic Chem., 2010. [source] Regioselectivity Control in the Metal-Catalyzed Functionalization of ,-Allenols, Part,2: Theoretical Study,CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2009Benito Alcaide Prof. Abstract Calculating cyclization: Theoretical work directed towards the elucidation of the mechanisms of the gold-, palladium-, and lanthanum-catalyzed oxycyclizations (5- exo versus 6- endo versus 7- endo) of ,-allenols has been pursued in close relationship with the experimental study (Part,1, accompanying paper) and has corroborated the bench results to provide a complete study of the reactivity of ,-allenols under different metal-catalyzed conditions. The gold-, palladium- and lanthanum-catalyzed oxycyclization reactions of azetidin-2-one-tethered ,-allenol derivatives to a variety of fused enantiopure tetrahydrofurans, dihydropyrans, and tetrahydrooxepines have been developed experimentally (Part,1, accompanying paper). The mechanisms of these regiocontrolled metal-catalyzed heterocyclization reactions have now been computationally explored at the DFT level (Part,2). The energies of the reaction intermediates and transition states for different possible pathways have been calculated in various model systems very close to the real system. Additionally, we selected the La[N(SiH3)2]3 complex to simulate the lanthanide amide precatalyst species. The agreement of theoretically predicted and experimentally observed selectivities is very good in all cases La reacción de heterociclación de , -alenoles catalizada por metales es un proceso regiocontrolado que da lugar a una amplia variedad de tetrahidrofuranos, tetrahidropiranos y tetrahidrooxepinas fusionadas enantiopuras, que contienen además un anillo ,-lactámico, que es la unidad estructural clave en productos biológicos relevantes como antibióticos e inhibidores enzimáticos. Se ha llevado a cabo un estudio teórico para la elucidación de los mecanismos de estas ciclaciones catalizadas por oro, paladio y lantano, en estrecha relación con el trabajo experimental (Parte,1, artículo anterior), corroborando los resultados obtenidos en el laboratorio. [source] [8+2] and [8+3] Cyclization Reactions of Alkenyl Carbenes and 8-Azaheptafulvenes: Direct Access to Tetrahydro-1-azaazulene and Cyclohepta[b]pyridinone DerivativesCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2008José Barluenga Prof. Abstract The reactivity of Fischer alkenyl carbenes toward 8-azaheptafulvenes is examined. Alkenyl carbenes react with 8-azaheptafulvenes with complete regio- and stereoselectivity through formal [8+3] and [8+2] heterocyclization reactions, which show an unprecedented dependence on the C, substituent at the alkenyl carbene complex. Thus, the formal [8+3] heterocyclization reaction is completely favored in carbene complexes that bear a coordinating moiety to give tetrahydrocyclohepta[b]pyridin-2-ones. Otherwise, alkenyl carbenes that lack appropriate coordinating groups undergo a formal [8+2] cyclization with 8-azaheptafulvenes to give compounds that bear a tetrahydroazaazulene structure. A likely mechanism for these reactions would follow well-established models and would involve a 1,4-addition/cyclization in the case of the [8+2] cyclization or a 1,2-addition/[1,2] shift,metal-promoted cyclization for the [8+3] reaction. The presence of a coordinating moiety in the carbene would favor the [1,2] metal shift through transition-state stabilization to lead to the [8+3] product. All these processes provide an entry into the tetrahydroazaazulene and cycloheptapyridone frameworks present in the structure of biologically active molecules. Se ha estudiado la reactividad de alquenilcarbenos de Fischer con 8-azaheptafulvenos. Los alquenilcarbenos reaccionan con 8-azaheptafulvenos a través de reacciones de heterociclación formales [8+3] y [8+2] con completa regioselectividad y estereoselectividad, mostrando una dependencia del sustituyente C, del complejo alquenilcarbeno sin precedentes. Así, en los complejos carbeno que contienen un resto coordinante la reacción de heterociclación formal [8+3] se favorece completamente para dar tetrahidrociclohepta[b]piridin-2-onas. Por otra parte, los alquenilcarbenos que carecen de grupos coordinantes apropiados, experimentan una ciclación formal [8+2] con los 8-azaheptafulvenos para dar compuestos con estructura de tetrahidroazuleno. Un mecanismo probable para estas reacciones se fundamenta en modelos bien establecidos e implica una adición 1,4/ciclación en el caso de la ciclación [8+2] o una adición 1,2/ciclación promovida por una migración 1,2 del metal en el caso de la reacción [8+3]. La presencia de un resto coordinante en el carbeno favorece la migración 1,2 del metal a través de una estabilización del estado de transición, conduciendo al producto [8+3]. Todos estos procesos representan una vía de acceso a los esqueletos de tetrahidroazuleno y cicloheptapiridona presentes en la estructura de moléculas biológicamente activas. [source] | ||||||||||||||||||||||