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Diazo Compounds (diazo + compound)
Selected AbstractsRhodium(II)-Catalyzed Inter- and Intramolecular Cyclopropanations with Diazo Compounds and Phenyliodonium Ylides: Synthesis and Chiral AnalysisHELVETICA CHIMICA ACTA, Issue 2 2005Ashraf Ghanem Different classes of cyclopropanes derived from Meldrum's acid (=2,2-dimethyl-1,3-dioxane-4,6-dione; 4), dimethyl malonate (5), 2-diazo-3-(silyloxy)but-3-enoate 16, 2-diazo-3,3,3-trifluoropropanoate 18, diazo(triethylsilyl)acetate 24a, and diazo(dimethylphenylsilyl)acetate 24b were prepared via dirhodium(II)-catalyzed intermolecular cyclopropanation of a set of olefins 3 (Schemes,1 and 4,6). The reactions proceeded with either diazo-free phenyliodonium ylides or diazo compounds affording the desired cyclopropane derivatives in either racemic or enantiomer-enriched forms. The intramolecular cyclopropanation of allyl diazo(triethylsilyl)acetates 28, 30, and 33 were carried out in the presence of the chiral dirhodium(II) catalyst [Rh2{(S)-nttl)4}] (9) in toluene to afford the corresponding cyclopropane derivatives 29, 31 and 34 with up to 37% ee (Scheme,7). An efficient enantioselective chiral separation method based on enantioselective GC and HPLC was developed. The method provides information about the chemical yields of the cyclopropane derivatives, enantioselectivity, substrate specifity, and catalytic activity of the chiral catalysts used in the inter- and intramolecular cyclopropanation reactions and avoids time-consuming workup procedures. [source] Reactions of ,,, -Enones with Diazo Compounds.HELVETICA CHIMICA ACTA, Issue 2 2004Part In this study, (E)- and (Z)-enones carrying only a phenyl substituent at their C(,) atom were treaced with dimethyl diazomalonate in the presence of (acetylacetonato)copper(II). According to the configuration of the starting enones, the products were dioxole or dihydrofuran derivatives, significant heterocycles in natural products. [source] ChemInform Abstract: Facile and Efficient Synthesis of Indazole Derivatives by 1,3-Cycloaddition of Arynes with Diazo Compounds and Azomethine Imides.CHEMINFORM, Issue 46 2009Tienan Jin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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] ChemInform Abstract: Reactions of Hydroxyl Group Containing Cyclic Acetals with Diazo Compounds.CHEMINFORM, Issue 16 2002D. A. Petrov 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] ChemInform Abstract: O-Alkylation of Amide Carbonyl Group with Diazo Compounds.CHEMINFORM, Issue 15 2002A New Way for Functionalizing Saccharin, Its Analogues. 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] Detection of hazardous reaction products during a thermal runawayPROCESS SAFETY PROGRESS, Issue 2 2003Ronald J. A. Kersten The control of major accident hazards linked with the storage and processing of dangerous substances in chemical and petrochemical installations is regulated in the European Union by the so-called "Seveso II Directive." One of the requirements in this Directive is the declaration of not only the hazardous substances as present onsite, but also any hazardous products that could form during a loss of control situation. This study focused on the development of an experimental technique to determine the substances that might be formed during an uncontrolled chemical reaction or runaway reaction. The decomposition reaction of a diazo compound was studied with the technique to assess its applicability. The results show that, apart from its applicability in relation to the Seveso II Directive, the same technique can be used to obtain data for the design of gas treatment systems or to study the mechanism behind runway reactions. Understanding this mechanism, in turn, helps to identify conditions that might favor the occurrence of, or might temper the course of, the runaway reaction. [source] An Efficient and Convenient Synthesis of Ethyl 1-(4-Methoxyphenyl)-5-phenyl-1H -1,2,3-triazole-4-carboxylateCHEMISTRY - AN ASIAN JOURNAL, Issue 2 2010Jung-Hsuan Chen Abstract The "click chemistry" of using organic azides and terminal alkynes is arguably the most efficient and straightforward route to the synthesis of 1,2,3-triazoles. In this paper, an alternative and direct access to ethyl 1-(4-methoxyphenyl)-5-phenyl-1H -1,2,3-triazole-4-carboxylate is described. Treatment of ethyl diazoacetate with 4-methoxyaniline derived aryl imines in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene provided fully substituted 1,2,3-triazoles in good to high chemical yields. The base-mediated reaction tolerates various substituted phenyl imines as well as ethyl diazoacetate or the more bulky diazoacetamide. A reasonable mechanism is proposed that involves the addition of an imine nitrogen atom to the terminal nitrogen atom of the diazo compound, followed by aromatization to give the 1,2,3-triazole. The presence of the 4-carboxy group is advantageous as it can be easily transformed into other functional groups. [source] X-ray Crystal Structure Study of Sterically Congested DiphenyldiazomethanesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2004Takashi Iikubo Abstract X-ray crystallographic structures were determined for five diphenyldiazomethanes (DDMs) with various ortho substituents, namely, bis(2,4,6-trichlorophenyl)diazomethane, bis(2,4,6-tribromophenyl)diazomethane, bis(4- tert -butyl-2,6-dibromophenyl)diazomethane, (4- tert -butyl-2,6-dimethylphenyl)(2,4,6-tribromophenyl)diazomethane, and [4- tert -butyl-2,6-bis(trifluoromethyl)phenyl](4- tert -butyl-2,6-dibromophenyl)diazomethane, and for bis(4-bromophenyl)diazomethane, a DDM with no ortho substituents. The correlation between the structural parameters, the ESR zero-field splitting (ZFS) parameters and the lifetimes of the triplet diphenylcarbenes (DPCs) generated from these diazo compounds was examined. It is noted that as ortho substituents are introduced onto the phenyl rings of the DDMs, the interplanar angle between the two phenyl rings increases, while the angle of the diazo carbon changes very little. DDM 6 -N2, from which the longest-lived triplet carbene is generated, is shown to have the largest interplanar angle of the DDMs examined. The bond distances between the aromatic carbons and the ortho substituents as well as the van der Waals radii of the substituents were also examined. These studies do not provide a quantitative correlation between the structural parameters of the precursor DDMs and the ZFS parameters and lifetimes of their photoproducts, triplet DPCs, but show how steric shielding of the ortho substituents affects the structures and stabilities of triplet DPCs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Cycloaddition Behavior of 1,2-Thiaphospholes: Reactions with Diazocumulenes and with CyclopentadieneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2003Jochen Kerth Abstract 1,2-Thiaphospholes 3a,b react with (1-diazo-2-oxoalkyl)silanes 1a,c to form [1,2]thiaphospholo[2,,3,:3,4][1,3]diphospholo[1,5- b][1,2]thiaphosphole systems 4 with cis - anti - cis configuration of the tricyclic framework. They are accompanied by small amounts of compounds 5 that are presumably the cis - syn - cis isomers of 4, and 6-alkylidene-1-phospha-2-thiabicyclo[3.1.0]hex-3-enes 6. It is likely that these reactions proceed by [3+2] cycloaddition of diazocumulenes, which coexist with diazo compounds as minor equilibrium components, at the P=C bond of the heterophospholes, followed by N2 elimination and formation of short-lived 2-alkylidene-1,2(,5)thiaphospholes. The latter can either add to excess thiaphosphole to form the tricyclic products or undergo electrocyclization to form bicyclic alkylidenephosphiranes. Thiaphosphole 3a does not seem to react directly with cyclopentadiene in a [4+2] or [2+4] cycloaddition. Reaction with excess cyclopentadiene at 120 °C yields the polycyclic compounds 15 and 16, which are likely to arise from a Diels,Alder reaction of 3a, reacting as a heterodiene, with the cyclopentadiene dimer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Rhodium(II)-Catalyzed Inter- and Intramolecular Cyclopropanations with Diazo Compounds and Phenyliodonium Ylides: Synthesis and Chiral AnalysisHELVETICA CHIMICA ACTA, Issue 2 2005Ashraf Ghanem Different classes of cyclopropanes derived from Meldrum's acid (=2,2-dimethyl-1,3-dioxane-4,6-dione; 4), dimethyl malonate (5), 2-diazo-3-(silyloxy)but-3-enoate 16, 2-diazo-3,3,3-trifluoropropanoate 18, diazo(triethylsilyl)acetate 24a, and diazo(dimethylphenylsilyl)acetate 24b were prepared via dirhodium(II)-catalyzed intermolecular cyclopropanation of a set of olefins 3 (Schemes,1 and 4,6). The reactions proceeded with either diazo-free phenyliodonium ylides or diazo compounds affording the desired cyclopropane derivatives in either racemic or enantiomer-enriched forms. The intramolecular cyclopropanation of allyl diazo(triethylsilyl)acetates 28, 30, and 33 were carried out in the presence of the chiral dirhodium(II) catalyst [Rh2{(S)-nttl)4}] (9) in toluene to afford the corresponding cyclopropane derivatives 29, 31 and 34 with up to 37% ee (Scheme,7). An efficient enantioselective chiral separation method based on enantioselective GC and HPLC was developed. The method provides information about the chemical yields of the cyclopropane derivatives, enantioselectivity, substrate specifity, and catalytic activity of the chiral catalysts used in the inter- and intramolecular cyclopropanation reactions and avoids time-consuming workup procedures. [source] On the Enantioselectivity of Transition Metal-Catalyzed 1,3-Cycloadditions of 2-Diazocyclohexane-1,3-dionesHELVETICA CHIMICA ACTA, Issue 9 2003Paul Müller The formal 1,3-cycloaddition of 2-diazocyclohexane-1,3-diones 1a,1d to acyclic and cyclic enol ethers in the presence of RhII -catalysts to afford dihydrofurans has been investigated. Reaction with a cis/trans mixture of 1-ethoxyprop-1-ene (13a) yielded the dihydrofuran 14a with a cis/trans ratio of 85,:,15, while that with (Z)-1-ethoxy-3,3,3-trifluoroprop-1-ene (13b) gave the cis -product 14b exclusively. The stereochemical outcome of the reaction is consistent with a concerted rather than stepwise mechanism for cycloaddition. The asymmetric cycloaddition of 2-diazocyclohexane-1,3-dione (1a) or 2-diazodimedone (=2-diazo-5,5-dimethylcyclohexane-1,3-dione; 1b) to furan and dihydrofuran was investigated with a representative selection of chiral, nonracemic RhII catalysts, but no significant enantioselectivity was observed, and the reported enantioselective cycloadditions of these diazo compounds could not be reproduced. The absence of enantioselectivity in the cycloadditions of 2-diazocyclohexane-1,3-diones is tentatively explained in terms of the Hammond postulate. The transition state for the cycloaddition occurs early on the reaction coordinate owing to the high reactivity of the intermediate metallocarbene. An early transition state is associated with low selectivity. In contrast, the transition state for transfer of stabilized metallocarbenes occurs later, and the reactions exhibit higher selectivity. [source] | ||||||||||||||||||||||