- Thermal Stability and Explosive Hazard Assessment of Diazo Compounds and Diazo Transfer Reagents
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Despite their wide use in academia as metal-carbene precursors, diazo compounds are often avoided in industry owing to concerns over their instability, exothermic decomposition, and potential explosive behavior. The stability of sulfonyl azides and other diazo transfer reagents is relatively well understood, but there is little reliable data available for diazo compounds. This work first collates available sensitivity and thermal analysis data for diazo transfer reagents and diazo compounds to act as an accessible reference resource. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and accelerating rate calorimetry (ARC) data for the model donor/acceptor diazo compound ethyl (phenyl)diazoacetate are presented. We also present a rigorous DSC dataset with 43 other diazo compounds, enabling direct comparison to other energetic materials to provide a clear reference work to the academic and industrial chemistry communities. Interestingly, there is a wide range of onset temperatures (Tonset) for this series of compounds, which varied between 75 and 160 °C. The thermal stability variation depends on the electronic effect of substituents and the amount of charge delocalization. A statistical model is demonstrated to predict the thermal stability of differently substituted phenyl diazoacetates. A maximum recommended process temperature (TD24) to avoid decomposition is estimated for selected diazo compounds. The average enthalpy of decomposition (?"HD) for diazo compounds without other energetic functional groups is-102 kJ mol-1. Several diazo transfer reagents are analyzed using the same DSC protocol and found to have higher thermal stability, which is in general agreement with the reported values. For sulfonyl azide reagents, an average ?"HD of-201 kJ mol-1 is observed. High-quality thermal data from ARC experiments shows the initiation of decomposition for ethyl (phenyl)diazoacetate to be 60 °C, compared to that of 100 °C for the common diazo transfer reagent p-acetamidobenzenesulfonyl azide (p-ABSA). The Yoshida correlation is applied to DSC data for each diazo compound to provide an indication of both their impact sensitivity (IS) and explosivity. As a neat substance, none of the diazo compounds tested are predicted to be explosive, but many (particularly donor/acceptor diazo compounds) are predicted to be impact-sensitive. It is therefore recommended that manipulation, agitation, and other processing of neat diazo compounds are conducted with due care to avoid impacts, particularly in large quantities. The full dataset is presented to inform chemists of the nature and magnitude of hazards when using diazo compounds and diazo transfer reagents. Given the demonstrated potential for rapid heat generation and gas evolution, adequate temperature control and cautious addition of reagents that begin a reaction are strongly recommended when conducting reactions with diazo compounds.
- Green, Sebastian P.,Wheelhouse, Katherine M.,Payne, Andrew D.,Hallett, Jason P.,Miller, Philip W.,Bull, James A.
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- Azide Radical Initiated Ring Opening of Cyclopropenes Leading to Alkenyl Nitriles and Polycyclic Aromatic Compounds
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We report herein a radical-mediated amination of cyclopropenes. The transformation proceeds through a cleavage of the three-membered ring after the addition of an azide radical on the strained double bond and leads to tetrasubstituted alkenyl nitrile derivatives upon loss of N2. With 1,2-diaryl substituted cyclopropenes, this methodology could be extended to a one-pot synthesis of highly functionalized polycyclic aromatic compounds (PACs). This transformation allows the synthesis of nitrile-substituted alkenes and aromatic compounds from rapidly accessed cyclopropenes using only commercially available reagents.
- Muriel, Bastian,Waser, Jerome
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p. 4075 - 4079
(2021/01/18)
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- B(C6F5)3-catalyzed O-H insertion reactions of diazoalkanes with phosphinic acids
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A highly efficient base-, metal-, and oxidant-free catalytic O-H insertion reaction of diazoalkanes and phosphinic acids in the presence of B(C6F5)3has been developed. This powerful methodology provides a green approach towards the synthesis of a broad spectrum of α-phosphoryloxy carbonyl compounds with good to excellent yields (up to 99% yield). The protocol features the advantages of operational simplicity, high atom economy, practicality, easy scalability and environmental friendliness.
- Jiang, Jun,Zhang, Xinzhi,Zhang, Yangyang,Zhao, Jincheng
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p. 5772 - 5776
(2021/07/12)
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- Three-Component Reaction for the Synthesis of Highly Functionalized Propargyl Ethers
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Multicomponent reactions provide efficient means to access molecular complexity. Herein, we report a copper-catalyzed three-component reaction of diazo compounds, alcohols and ethynyl benziodoxole (EBX) reagents for the synthesis of propargyl ethers. Extensive variations of the three partners of the reaction is possible, leading to highly functionalized and structurally diverse products under mild conditions. Alkynylation of a copper ylide intermediate is postulated as key step for this transformation.
- Pisella, Guillaume,Gagnebin, Alec,Waser, Jér?me
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p. 10199 - 10204
(2020/07/17)
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- Photochemical, Metal-Free Sigmatropic Rearrangement Reactions of Sulfur Ylides
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Sigmatropic rearrangement reactions constitute one of the most fundamental reactions of carbenes. While state-of-the-art synthetic methods require the use of expensive precious metal catalysts, the application of visible light for the photolysis of α-aryldiazoacetates is much less investigated and provides an operationally simple entry to carbenes under mild reaction conditions. Herein, we report on blue-light induced sigmatropic rearrangement reactions of sulfur compounds with α-aryldiazoacetates. This process, depending on the substitution pattern of the sulfide, opens up formal insertion reactions of carbenes into S?N, S?C, or C?H bonds.
- Yang, Zhen,Guo, Yujing,Koenigs, Rene M.
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supporting information
p. 6703 - 6706
(2019/05/10)
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- Enantioselective rhodium-catalysed insertion of trifluorodiazoethanes into tin hydrides
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Aryl substituted 2,2,2-trifluorodiazoethanes undergo rhodium(II)-catalysed insertion reactions with tin hydrides affording the corresponding α-(trifluoromethyl)benzyl stannanes. This reactivity contrasts with that of diazo esters which predominantly afford CH2 reduction products in the presence of tin hydrides. The first example of asymmetric insertion into tin hydrides using diazo compounds is also described. In addition, this system extends to asymmetric germanium hydride and silane insertion.
- Hyde, Stephen,Veliks, Janis,Ascough, David M.H.,Szpera, Robert,Paton, Robert S.,Gouverneur, Véronique
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- Fluoroalkyl-Substituted Diazomethanes and Their Application in a General Synthesis of Pyrazoles and Pyrazolines
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A novel continuous-flow approach for the synthesis of fluoroalkyl-substituted diazomethanes has been developed. Utilizing a cheap, self-made microreactor fluoroalkyl-substituted amines were transformed into the corresponding diazomethanes using tert-butyl nitrite and acetic acid as catalyst. These diazomethanes were employed in [2+3] cycloaddition reactions with olefins and alkynes, yielding valuable pyrazolines and pyrazoles in good to excellent yields.
- Mertens, Lucas,Hock, Katharina J.,Koenigs, Rene M.
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supporting information
p. 9542 - 9545
(2016/07/14)
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- Diversity-oriented approach to CF3CHF-, CF3CFBr-, CF3CF2-, (CF3)2CH-, and CF3(SCF3)CH-substituted arenes from 1-(Diazo-2,2,2-trifluoroethyl)arenes
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Arenes substituted with perfluoroalkyl groups are attractive targets for drug and agrochemical development. Exploiting the carbenic character of donor/acceptor diazo compounds, a diversity-oriented synthesis of perfluoroalkylated arenes, for late stage fluorofunctionalization, is described. The reaction of 1-(diazo-2,2,2-trifluoroethyl)arenes with HF, F/Br, F2, CF3H, and CF3SH sources give direct access to a variety of perfluoroalkyl-substituted arenes presenting with incremental fluorine content. The value of this approach is also demonstrated for radiochemistry and positron emission tomography with the [18F]-labeling of CF3CHF-, CF3CBrF-, and CF3CF2-arenes from [18F]fluoride.
- Emer, Enrico,Twilton, Jack,Tredwell, Matthew,Calderwood, Samuel,Collier, Thomas Lee,Ligault, Benot,Taillefer, Marc,Gouverneur, Vronique
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p. 6004 - 6007
(2015/01/09)
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- Enantioselective synthesis of trifluoromethyl-substituted cyclopropanes
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Equation Presented The reaction of 1-aryl-2,2,2-trifluorodiazoethanes with alkenes, catalyzed by the adamantylglycine-derived dirhodium complex Rh 2(R-PTAD)4, generates trifluoromethyl-substituted cyclopropanes with high diastereosel
- Denton, Justin R.,Sukumaran, Dinesh,Davies, Huw M. L.
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p. 2625 - 2628
(2008/02/10)
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- A Facile Synthesis of α-Trifluorodiazo Compounds
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A variety of α-trifluorodiazo compounds which can be used as building blocks for the construction of organic molecules bearing a trifluoromethyl group have been prepared in high yields simply by refluxing trifluoromethylketone 2,4,6-triisopropylbenzenesul
- Shi, Guoqiang,Xu, Yuanyao
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p. 173 - 178
(2007/10/02)
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- Regioselectivity in the Addition of Singlet and Triplet Carbenes to 1,1-Dimethylallene. A Probe for Carbene Multiplicity
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Singlet carbenes add preferentially to the more substituted bond of 1,1-dimethylallene (1), to give methylenecyclopropanes 3 as the major product.In contrast, many triplet carbenes add with differing regioselectivity, giving the thermodynamically preferre
- Creary, Xavier
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p. 1611 - 1618
(2007/10/02)
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