- Cracking under internal pressure: Photodynamic behavior of vinyl azide crystals through N2release
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When exposed to UV light, single crystals of the vinyl azides 3- azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with the release of N2. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals. While the crystals of 1a delaminate and release gaseous N2 indiscriminately under paraffin oil, the crystals of 1b and 1c visibly expand, bend, and fracture, mainly along specific crystallographic faces, before releasing N2. The photochemical analysis suggests that the observed expansion is due to internal pressure exerted by the gaseous product in the crystal lattices of these materials. Lattice energy calculations, supported by nanoindentation experiments, show significant differences in the respective lattice energies. The calculations identify critical features in the crystal structures of 1b and 1c where elastic energy accumulates during gas release, which correspond to the direction of the observed cracks. This study highlights the hitherto untapped potential of photochemical gas release to elicit a photomechanical response and motility of photoreactive molecular crystals.
- Shields, Dylan J.,Karothu, Durga Prasad,Sambath, Karthik,Ranaweera, Ranaweera A. A. Upul,Schramm, Stefan,Duncan, Alexander,Duncan, Benjamin,Krause, Jeanette A.,Gudmundsdottir, Anna D.,Naumov, Pan?e
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p. 18565 - 18575
(2020/12/01)
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- Harnessing Stereospecific Z-Enamides through Silver-Free Cp?Rh(III) Catalysis by Using Isoxazoles as Masked Electrophiles
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The stereospecific synthesis of Z-enamides is described in this paper. For the first time, isoxazoles have been employed as electrophiles in C-H functionalization to afford thermodynamically less stable Z-enamides utilizing salicylaldehydes in an atom- and step-economic fashion. The stereochemistry of enamides might originate from the relative disposition of atoms present in isoxazole and the intramolecular hydrogen bonding. The reaction showed excellent scope as several structurally and electronically diverse salicylaldehydes and isoxazoles reacted efficiently.
- Debbarma, Suvankar,Bera, Sourav Sekhar,Maji, Modhu Sudan
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supporting information
p. 835 - 839
(2019/01/26)
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- Preparation method of isoxazole derivative
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The invention relates to a preparation method of an isoxazole derivative, which comprises the following steps of mixing an propargyl alcohol derivative, a halogen source, an acid and a solvent, and heating to react; adding the hydroxylamine into the react
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Paragraph 0066-0071
(2019/12/02)
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- A novel synthesis of 5-substituted isoxazoles from propargylic amines and N-hydroxyphthalimide
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A mild and efficient method for the synthesis of 5-substituted isoxazoles through cyclization of propargylic amines with N-hydroxyphthalimide (NHPI) under metal-free conditions was developed.
- Zhang, Yicheng,Chen, Wei,Jia, Xueshun
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supporting information
p. 2181 - 2183
(2018/05/08)
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- TEMPO-catalyzed synthesis of 5-substituted isoxazoles from propargylic ketones and TMSN3
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A novel and efficient TEMPO-catalyzed synthesis of 5-substituted isoxazoles from propargylic ketones and TMSN3via a radical mechanism process is described. This methodology provides an easy access to a variety of useful 5-substituted isoxazoles
- He, Yan,Xie, Yu-Yang,Wang, Ying-Chun,Bin, Xiao-Min,Hu, Da-Chao,Wang, Heng-Shan,Pan, Ying-Ming
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p. 58988 - 58993
(2016/07/06)
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- Reactions of trans-1-(β-aroylvinyl)pyridinium bromides with hydroxylamine hydrochloride
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Reactions of trans-1-(β-aroylvinyl)pyridinium bromides with hydroxylamine hydrochloride lead to a mixture of substituted isoxazoles regardless of the substituent nature in the aromatic core and the solvent.
- Khachikyan, R. Dzh.,Hovakimyan,Panosyan,Tamazyan,Ayvazyan
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p. 1078 - 1081
(2015/06/25)
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- An efficient synthesis of isoxazoles and pyrazoles under ultrasound irradiation
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A series of 5-arylisoxazole and 5-aryl-1H-pyrazole derivatives was synthesized by the reaction of 3-(dimethylamino)-1-arylprop-2-en-1-one with hydroxylamine hydrochloride or hydrazine hydrate under ultrasound irradiation without using any catalyst. This m
- Huang, Zhi-Bin,Li, Li-Li,Zhao, Yan-Wei,Wang, Hui-Yuan,Shi, Da-Qing
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p. E309-E313
(2014/11/07)
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- Clean and efficient synthesis of isoxazole derivatives in aqueous media
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A series of 5-arylisoxazole derivatives were synthesized via the reaction of 3-(dimethyl-amino)-1-arylprop-2-en-1-ones with hydroxylamine hydrochloride in aqueous media without using any catalyst. This method has the advantages of easier work-up, mild rea
- Dou, Guolan,Xu, Pan,Li, Qiang,Xi, Yukun,Huang, Zhibin,Shi, Daqing
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p. 13645 - 13653
(2014/01/06)
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- Reaction of β-dimethylaminovinyl ketones with hydroxylamine: A simple and useful method for synthesis of 3- and 5-substituted isoxazoles
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(Chemical Equation Presented) The regioselective synthesis of 3- and 5-substituted-isoxazoles from the reaction of β-dimethylaminovinyl ketones [R-C(O)CH=CH-NMe2, where R = Ph, MeO-4-C6H4, F-4-C6H4, C
- Rosa, Fernanda A.,Machado, Pablo,Bonacorso, Helio G.,Zanatta, Nilo,Martins, Marcos A. P.
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p. 879 - 885
(2008/09/21)
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- New Synthesis of Pyrazole and Isoxazole Derivatives
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A convenient synthesis of 5-aryl-1-phenylpyrazoles and 5-arylisoxazoles, from readily available ketimine 1 dimethylformamide dimethylacetal and phenylhydrazine or hydroxylamine, is described.
- Molina, P.,Fresneda, P. M.
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p. 461 - 464
(2007/10/02)
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- New Synthesis of Isoxazoles and Isothiazoles. A Convenient Synthesis of Thioenaminones from Enaminones
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The reaction of 1-aryl-3-(dimethylamino)-2-propene-1-ones (enaminones) and 1-aryl-3-(dimethylamino)-2-propene-1-thiones (thioenaminones) with hydroxylamine-O-sulfonic acid gave, respectively, isoxazoles in 76-84 percent yields and isothiazoles in 60-65 pe
- Lin, Yang-i,Lang, Stanley, A.
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p. 4857 - 4860
(2007/10/02)
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