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Cycloaddition
Kinds of Cycloaddition Terms modified by Cycloaddition Selected AbstractsStrong Evidence for an Unprecedented Borderline Case of Dissociation and Cycloaddition in Open-Shell 1,3-Dipole Chemistry: Transient Nitrilium Phosphane-Ylide Complex Radical CationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009Holger Helten Abstract The reaction of 3-ferrocenyl-substituted 2H -azaphosphirene complexes 1a,c in the presence of substoichiometric amounts of ferrocenium hexafluorophosphate yields 3,5-diferrocenyl-substituted 2H -1,4,2-diazaphosphole complexes 3a,c and difluoro(organo)phosphane complexes 4a,c. The reaction of 1a,c and [FcH]PF6 with cyanoferrocene yields 3a,c in a straightforward way. The molecular structures of 3a,c were unambiguously identified by multinuclear NMR spectroscopic experiments, mass spectrometry, and single-crystal X-ray diffraction studies. DFT calculations on model complexes 1d,m and 3d,m reveal a close similarity of Mo and W complexes (vs. Cr) and a strong influence of the ferrocenyl substituent on the geometry, spin, and charge distribution of reactive intermediates and the reaction course. Strong support for the assumption of a dissociation,cycloaddition reaction sequence leading to 3 and thus a surprising "cannibalistic" reaction was obtained.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis of (1,2,4-Oxadiazole)palladium(II) Complexes by [2 + 3] Cycloaddition of Nitrile Oxides to Organonitriles in the Presence of PdCl2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2005Nadezhda A. Bokach Abstract The reaction between the nitrile oxides 2,4,6-R3C6H2CNO (R = Me, OMe) and trans -[PdCl2(RCN)2], or RCN (R = Me, Et, CH2CN, NMe2, Ph) in the presence of PdCl2, proceeded smoothly under mild conditions and allowed the isolation of the 1,2,4-oxadiazole complexes trans -[PdCl2{Na=C(R)-ON=Cb(C6H2R3)(Na,Cb)}2] (1,8) in 40,85,% yields. In CH2Cl2, the reaction between 2,4,6-R3C6H2CNO and [PdCl2(MeCN)2] furnishes [PdCl2(ONCC6H2R3)2] (9 and 10), which are the first representatives of metal compounds where nitrile oxides act as ligands. The 1,2,4-oxadiazole complexes 1,8 were characterized by elemental analysis, FAB mass spectrometry, and IR, 1H and 13C{1H} NMR spectroscopy, while 2, 3, 7, and 8 were additionally characterized by X-ray crystallography. The liberation of the heterocyclic species from 1,8 was successfully performed by substitution reaction either with 1,2-bis(diphenylphosphanyl)ethane or with an excess amount of Na2S·7H2O in MeOH; the liberated 1,2,4-oxadiazoles (11,18) were characterized by positive-ion FAB mass spectrometry and 1H and 13C{1H} NMR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Unsupported Copper Nanoparticles in the 1,3-Dipolar Cycloaddition of Terminal Alkynes and Azides,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2010Francisco Alonso Abstract Readily prepared copper nanoparticles were found to catalyse the 1,3-dipolar cycloaddition of azides and alkynes up to rates comparable to those of microwave chemistry. Both the preparation of the nanoparticles and the click reaction are carried out under mild conditions, in short reaction times and in the absence of any stabilising additive or ligand. A variety of 1,2,3-triazoles were prepared in excellent yields. A reaction mechanism was postulated on the basis of different reactivity studies and deuteration experiments. Copper(I) acetylides were demonstrated to be the real intermediate species. [source] Sequential 1,3-Dipolar Cycloaddition of Nitrones to ,-(2-Aminophenyl) ,,,-Ynones and Cyclocondensation: A New Entry to the Isoxazolino[4,5- c]quinoline RingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2009Giorgio Abbiati Abstract The reaction of ,-(2-aminophenyl) ,,,-ynones with N -methyl nitrones provides a simple and efficient entry to the isoxazolino[4,5- c]quinoline ring system through a sequential 1,3-dipolar cycloaddition/annulation process. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Straightforward Strategy for the Stereoselective Synthesis of Spiro-Fused (C-5)Isoxazolino- or (C-3)Pyrazolino-(C-3)quinolin-2-ones from Baylis,Hillman Adducts by 1,3-Dipolar Cycloaddition and Reductive Cyclization,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 32 2008Virender Singh Abstract A straightforward and general approach for the stereoselective synthesis of spiro-fused (C-5)isoxazolino- or (C-3)pyrazolino-(C-3)quinolin-2-ones from the adducts offorded from the Baylis,Hillman reaction of 2-nitrobenzaldehyde and ethyl acrylate by sequential 1,3-dipolar cycloaddition and reductive cyclization is presented. It was found that the reductive cyclization of the isoxazoline derivatives proceeded efficiently in the presence of In/HCl, whereas similar reductions of pyrazolines gave better yields when carried out in the presence of an Fe/AcOH mixture. However, similar attempts employing the Baylis,Hillman adduct of 2-nitrobenzaldehyde and methyl vinyl ketone did not yield the desired compounds.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Highly Regio- and Stereoselective Diels,Alder Cycloaddition of Difluoro(methylene)cyclopropanesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2008Xiao-Chun Hang Abstract The Diels,Alder reactions of difluoro(methylene)cyclopropanes (F2MCPs) with cyclic dienes are described. These cycloaddition reactions exhibited complete regioselectivity and high endo -stereoselectivity. The obtained cycloadducts underwent a retro-Diels,Alder reaction to give the original dienophiles and dienes when heated, reflecting the reversible Diels,Alder reactivity of F2MCPs.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] An Efficient and Diastereoselective Intramolecular 1,3-Dipolar Cycloaddition of Cyclic Azomethine Ylides and NitronesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2006Rafael Pedrosa Abstract Nitrones and azomethine ylides formed by condensation of chiral 2-formyl-perhydro benzoxazines and N -substituted hydroxylamines or cyclic ,-amino acids cyclize intramolecularly yielding polycyclic isoxazolidine or pyrrolidine derivatives, respectively, with total diastereoselectivity. On the contrary, stabilized azomethine ylides derived from methyl prolinate undergo the cyclization products in very low yields.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Fused Tetracyclic Heterocycles by Thermally Initiated Intramolecular Criss-Cross Cycloaddition of 3-Substituted HomoallenylaldazinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2005Hana Zachová Abstract The thermally initiated intramolecular criss-cross cycloaddition of 3-substituted homoallenylaldazines 5 has been explored. Their cyclization led to interesting new fused heterocyclic systems 6 consisting of four five-membered rings with two nitrogen heteroatoms. The azines were prepared by the reaction of homoallenyl aldehydes 4 with hydrazine. The homoallenyl aldehydes 4 were synthesized by the Claisen rearrangement of new N,N -disubstituted 4-[(2-methylprop-1-en-1-yl)oxy]but-2-yn-1-amines 3a,f prepared by Mannich reaction of 2-methylprop-1-en-1-yl prop-2-yn-1-yl ether (2). The success of the reaction was based on the improved solvent-free synthesis of 1-chloro-2-methylpropyl prop-2-yn-1-yl ether (1) and its conversion to isolable 2-methylprop-1-en-1-yl prop-2-yn-1-yl ether (2) in high yield. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The Formation of Silylated ,-Lactams from Silylketenes through Lewis Acid Promoted [2+2] Cycloaddition: A Combined Theoretical and Experimental StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2005Béatrice Pelotier Abstract The stereoselective formation of silylated cis -,-lactams from (trimethylsilyl)ketene and an ,-imino ester by Lewis acid catalysis is described. Theoretical results suggest that the reaction between (trimethylsilyl)ketene and trans -(methoxycarbonyl)- N -methylformaldimine would proceed most favourably with the BF3 catalyst coordinated to the ketene. Moreover, the calculated energy barriers account for the cis:trans ratio found experimentally. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis and Some Chemical Transformations of (Z)- and (E)-2-Acetyl-1-ferrocenyl-3-methylbuta-1,3-dienes , A New Type of Cationic CycloadditionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2004Elena I. Klimova Abstract Dehydration of (E)- and (Z)-2-acetyl-1-ferrocenyl-3-methylbut-1-en-3-ols gave the corresponding (E)- and (Z)-2-acetyl-1-ferrocenyl-3-methylbuta-1,3-dienes, which have a cross-conjugated system of three double bonds. These heterotrienes readily afford the products of linear and cyclodimerization by following a cationic cyclodimerization mechanism; they also form Diels,Alder adducts with azodicarboxylic and maleic acid N -phenylimides. The spatial structures of (E)-2-acetyl-1-ferrocenyl-3-methylbuta-1,3-diene, (E,E)-1,5-diferrocenyl-2-isopropenyl-6-isopropylidene-3-methyl-1,3-octadiene-7-one, and 7-ferrocenyl-4-(ferrocenylmethylidene)-8-isopropylidene-1,3,5-trimethyl-9-oxabicyclo[3.3.1]non-2-ene were elucidated by X-ray diffraction analyses of single crystals. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] 3-Tocopherylisoxazolines by [2+3] CycloadditionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2004Thomas Rosenau Abstract New isoxazoline derivatives of ,-tocopherol (1), the main component of vitamin E, were synthesized in a facile, two-step sequence consisting of nitration followed by 1,3-dipolar cycloaddition. 5-Nitromethyl-,-tocopheryl acetate (3), obtained from the cheap ,-tocopheryl acetate (2) by direct nitration in one step, acted as the nitrile oxide precursor in the reaction with various alkenes. The facile conversion proceeded in the presence of equimolar amounts of PhNCO and catalytic amounts of triethylamine. The NMR spectra of the product isoxazolines 5,13, showing strongly temperature-dependent resonances of the 4,,-CH, 4-CH2 and the acetyl group, are discussed, and the crystal structures of model compounds containing a methyl group instead of the isoprenoid side chain are presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] [2+2+2]-Cycloaddition of 4-Hydroxy-Substituted Enediynes to 2-Hydroxy-Substituted DecahydrophenanthrenesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2003Ulrich Groth Abstract Enediynes rac - 4 were prepared in seven steps with an overall yield of 31% starting from 4-pentyn-1-ol (5). A cobalt mediated [2+2+2]-cycloaddition of these enediynes and subsequent removal of the metal fragment afforded the decahydrophenanthrenes rac - 3/13 in 37,56% yield. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Regioselective Synthesis of 4-(Arylsulfanyl)-2-hydroxyhomophthalates by [4+2] Cycloaddition of 3-(Arylsulfanyl)-1-(trimethylsilyloxy)buta-1,3-dienes with Dimethyl Penta-2,3-dienedioateHELVETICA CHIMICA ACTA, Issue 4 2010Muhammad Imran Abstract The [4+2] cycloaddition of 3-(arylsulfanyl)-1-(trimethylsilyloxy)buta-1,3-dienes with dimethyl penta-2,3-dienedioate provides a convenient and regioselective approach to a variety of 4-(arylsulfanyl)-2-hydroxyhomophthalates. [source] Microwave-Induced Stereocontrol of , -Lactam Formation with an N -Benzylidene-9,10-dihydrophenanthren-3-amine via Staudinger CycloadditionHELVETICA CHIMICA ACTA, Issue 2 2010Debasish Bandyopadhyay Abstract The synthesis of 3-substituted 4-phenyl-1-(9,10-dihydrophenanthren-3-yl)azetidin-2-ones was achieved following Staudinger cycloaddition under microwave-induced conditions. The stereoselectivity of , -lactam formation depended on the power level of the microwave irradiation used in the experiments. [source] 2-Azido-2-deoxycellulose: Synthesis and 1,3-Dipolar CycloadditionHELVETICA CHIMICA ACTA, Issue 4 2008Fuyi Zhang Abstract Chitosan (1) was prepared by basic hydrolysis of chitin of an average molecular weight of 70000 Da, 1H-NMR spectra indicating almost complete deacetylation. N -Phthaloylation of 1 yielded the known N -phthaloylchitosan (2), which was tritylated to provide 3a and methoxytritylated to 3b. Dephthaloylation of 3a with NH2NH2,H2O gave the 6- O -tritylated chitosan 4a. Similarly, 3b gave the 6- O -methoxytritylated 4b. CuSO4 -Catalyzed diazo transfer to 4a yielded 95% of the azide 5a, and uncatalyzed diazo transfer to 4b gave 82% of azide 5b. Further treatment of 5a with CuSO4 produced 2-azido-2-deoxycellulose (7). Demethoxytritylation of 5b in HCOOH gave 2-azido-2-deoxy-3,6-di- O -formylcellulose (6), which was deformylated to 7. The 1,3-dipolar cycloaddition of 7 to a range of phenyl-, (phenyl)alkyl-, and alkyl-monosubstituted alkynes in DMSO in the presence of CuI gave the 1,2,3-triazoles 8,15 in high yields. [source] Reactions of 2-Unsubstituted 1H -Imidazole 3-Oxides with 2,2-Bis(trifluoromethyl)ethene-1,1-dicarbonitrile: A Stepwise 1,3-Dipolar CycloadditionHELVETICA CHIMICA ACTA, Issue 7 2006Grzegorz Mlosto Abstract The reaction of 1,4,5-trisubstituted 1H -imidazole-3-oxides 1 with 2,2-bis(trifluoromethyl)ethene-1,1-dicarbonitrile (7, BTF) yielded the corresponding 1,3-dihydro-2H -imidazol-2-ones 10 and 2-(1,3-dihydro-2H -imidazol-2-ylidene)malononitriles 11, respectively, depending on the solvent used. In one example, a 1,:,1 complex, 12, of the 1H -imidazole 3-oxide and hexafluoroacetone hydrate was isolated as a second product. The formation of the products is explained by a stepwise 1,3-dipolar cycloaddition and subsequent fragmentation. The structures of 11d and 12 were established by X-ray crystallography. [source] N - and C -acyclic thionuleoside analogues of 1,2,3-triazoleHETEROATOM CHEMISTRY, Issue 5 2004Najim A. Al-Masoudi Cycloaddition of the azide derivative 5 with 1,4-dihydroxybutyne afforded the N -thio-acyclic nucleoside 6, which prepared alternatively from coupling of the bromo derivative 8 with 2-acetoxy-ethylmercaptan. Deblocking of 6 gave the free nucleoside 7. Mesylation of 6 furnished the dimesylate 9, which gave three rearranged products 14,16 on treatment with chloride anion. These compounds might be obtained via the episulfonium ion 10, which is subjected to nucleophilic displacement and further sulfur participation. Deblocking of 14,16 afforded the free nucleoside analogues 17,19, and their structures were confirmed by COSY, ROESY, HMQC, and HMBC NMR techniques. Compound 16 was prepared alternatively from chlorination of alcohol 6 with Ph3P-CCl4. Carbomoylation of 6 led to the carbamate 20, which gave the free nucleoside analogue 21 on deblocking. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:380,387, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20030 [source] Cycloaddition of nitrile oxides to substituted vinylphosphonatesHETEROATOM CHEMISTRY, Issue 4 2003Yong Ye Cycloaddition of nitrile oxides to substituted vinylphosphonates was performed. A series of 4,5-dihydroisoxazoles containing phosphonyl group were synthesized under very mild condition in excellent regiospecificity. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:309,311, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10149 [source] Cycloaddition of bis-1,3-dipolar reagents to 1,3-diarylprop-2-en-1-onesHETEROATOM CHEMISTRY, Issue 4 2003V. Padmavathi Bis pyrazolines and isoxazolines were prepared by 1,3-dipolar cycloaddition of benzene-1,3/1,4-dicarboxaldehyde dihydrazones and dioximes to 1,3-diaryl-prop-2-en-1-ones. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:379,383, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10169 [source] Enantioselective Synthesis of Spirocyclic Oxindole-,-lactones via N-Heterocyclic Carbene-Catalyzed Cycloaddition of Ketenes and IsatinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Xiao-Na Wang Abstract Chiral N-heterocyclic carbenes were found to be efficient catalysts for the formal [2+2] cycloaddition reaction of disubstituted ketenes and isatins to give the corresponding spirocyclic oxindole-,-lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Ring opening with Grignard reagents or decarboxylation of the oxindole spirocyclic-,-lactone gave the corresponding 3-hydroxy- or 3-alkylenyloxindoles in good yields. [source] Copper(I) Acetate: A Structurally Simple but Highly Efficient Dinuclear Catalyst for Copper-Catalyzed Azide-Alkyne CycloadditionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Changwei Shao Abstract In this article, the structurally well-defined dinuclear complex copper(I) acetate was studied in detail and was developed as a highly practical and efficient catalyst for the copper(I)-catalyzed azide-alkyne cycloaddition. The "bare" phenylethynylcopper(I) (i.e., with no exogeneous ligands) was isolated as an intermediate, which can be converted into an active catalytic species by treatment with acetic acid (in situ produced in the reaction) to efficiently catalyze the azide-alkyne cycloaddition under mild conditions. [source] Polymer-Supported 1,5,7-Triazabicyclo[4.4.0]dec-5-ene as Polyvalent Ligands in the Copper-Catalyzed Huisgen 1,3-Dipolar CycloadditionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Alberto Coelho Abstract New supported catalysts for the Huisgen's [3+2],azide-alkyne cycloaddition have been prepared by immobilization of copper species on commercially available polymeric matrixes incorporating the 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) template. The synergic exploitation of the exceptional copper chelating ability and basicity profile of the TBD framework, in addition to ensuring effective immobilization and stabilization of copper species, allows the implementation of three-component strategies. The new catalytic systems enabled the development of regioselective, efficient, modular, mild and eco-friendly multicomponent syntheses of diversely decorated 1,2,3-triazoles, contributing to expand the scope and versatility of the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition. [source] Immobilization of MacMillan Imidazolidinone as Mac-SILC and its Catalytic Performance on Sustainable Enantioselective Diels,Alder CycloadditionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Hisahiro Hagiwara Abstract MacMillan's imidazolidinone catalyst was immobilized as a supported ionic liquid catalyst (Mac-SILC) in the pores of silica gel with the aid of an ionic liquid , 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The heterogenized organocatalyst was utilized for the enantioselective Diels,Alder reaction of cyclopentadiene and cinnamaldehyde, recovered by simple filtration and subsequent evacuation, and repeatedly used up to six times in 81% average chemical yield, 87% ee for endo - and 80% ee for exo -products. The Mac-SILC was effective for a variety of substrates. [source] Silver Acetate/TF-BiphamPhos-Catalyzed endo -Selective Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides with Vinyl Phenyl SulfoneADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Gang Liang Abstract The first catalytic endo -selective 1,3-dipolar cycloaddition of azomethine ylides and vinyl phenyl sulfone has been developed successfully. The highly efficient silver acetate (AgOAc)/TF-BiphamPhos catalytic system exhibited high reactivity, excellent diastereoselectivity (>98:2), good enantioselectivity (67,92% ee) and broad substrate scope under mild conditions. [source] Enantioselective Synthesis of Dihydrocoumarins via N-Heterocyclic Carbene-Catalyzed Cycloaddition of Ketenes and o -Quinone MethidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Hui Lv Abstract Chiral N-heterocyclic carbenes were found to be efficient catalysts for the formal [4+2],cycloaddition reaction of alky(aryl)ketenes and o -quinone methides to give the corresponding 3,3,4-trisubstituted 3,4-dihydrocoumarins in good yields with good diastereoselectivities and excellent enantioselectivities. [source] Catalytic Asymmetric Cycloaddition of Carbon Dioxide and Propylene Oxide Using Novel Chiral Polymers of BINOL-Salen- Cobalt(III) SaltsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Peng Yan Abstract Four new chiral polymers of BINOL-Salen-cobalt(III) salt complexes have been designed, synthesized and applied to the direct fabrication of chiral propylene carbonate from racemic propylene oxide. The (R/S)-polymer catalyst 2 and (S/R)-polymer catalyst 4 exhibit better enantioselectivity than the (R/R)-polymer catalyst 1 and the (S/S)-polymer catalyst 3 and have been recovered and reused more than ten times without loss of activity and enantioselectivity. [source] A Straightforward Procedure for the [2+2+2],Cycloaddition of EnediynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Anaïs Geny Abstract Enediynes undergo intramolecular [2+2+2],cycloaddition in the presence of cobalt(II) iodide (CoI2), manganese and an N-heterocyclic carbene (IPr) generated in situ from the corresponding imidazolium salt and butyllithium (BuLi). Polycyclic cyclohexadienes are obtained selectively. This new method represents an interesting alternative to those employing air-sensitive cyclopentadienylcobalt [CpCoL2 (L=CO, C2H4)] catalysts. Moreover, the N-heterocyclic carbene can be used catalytically, which is a significant improvement compared to the corresponding phosphine-based system which requires an excess of ligand. [source] A Facile and Efficient Synthesis of Dihydroisobenzofuran Derivatives via Tandem Palladium-Catalyzed Coupling, Propargyl-Allenyl Rearrangement, [4+2],Cycloaddition and Aromatization ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2008Ruwei Shen Abstract A variety of dihydroisobenzofuran derivatives has been prepared in good yields via an interesting sequential reaction consisting of palladium-catalyzed coupling, propargyl-allenyl rearrangement, [4+2],cycloaddition and aromatization. A double-coupling, rearrangement, [4+2],cycloaddition and aromatization process is also described for the synthesis of more complex and diverse structures. [source] Use of some aryl and heteroaryl nitrilimines and nitrones in the synthesis of spiroheterocyclesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2004Eva Jedlovská 1,3-Dipolar cycloadditions of C-(5-nitro-2-furyl)- N -methyl nitrilimine (2a), C -(5-nitro-2-furyl)- N -phenyl nitrilimine (2b), C -4-nitrophenyl- N -methyl nitrilimine (2c) and C,N -diphenyl nitrilimine (2d) with 1-R-substituted 3,3-methylene-5,5-dimethylpyrrolidin-2-ones (1a-d) where R is H, acetyl, 1,1-dimethylethoxycarbonyl and 1-methylethenyl proceed with complete regioselectivity in good yields to afford 1,3,7-trisubstituted-6-oxo-8,8-dimethyl-1,2,7-triazaspiro[4,4]non-2-enes (5a-g) exclusively. Cycloaddition of C -(5-nitro-2-furyl)- N -phenylnitrone (3b) to the exocyclic double bond of the dipolarophile 1a proceeds to 2-phenyl-3-(5-nitro-2-furyl)-6-oxo-8,8-dimethyl-1-oxa-2,7-diazaspiro[4,4]nonane (7) with complete regio- and stereoselectivity. [source] Reaction of tetraazathiapentalene and thiadiazolopyrimidine derivatives with heterocumulenes: Cycloaddition and elimination reactions via hypervalent sulfur intermediatesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2004Noboru Matsumura Tetraazathiapentalene derivative 1 reacts with heterocumulenes such as diphenylketene (2) and 2-pyridylisothiocyanate (5) to give heterocycles 3, 6 and 7 with elimination of methylisothiocyanate. The reactions of thiadiazolopyrimidine derivatives 8a-b with ethoxycarbonyl isothiocyanate (9) and carbon disulfide (11) gives heterocycles 10 and 12 via thermal decomposition of 1:1 cycloadducts C and D which have a hypervalent sulfur. The mechanistic and reactivity features of these reactions are described. [source] | |||||||||||||||||||||||||||||||