- Study of the Features of the Reaction of Arylcyclopropanes with Nitrozonium Ethyl Sulfate or Nitrozonium Tetrafluoroborate
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Abstract: The reactions of diaryl-, aryl-, and alkyl–arylcyclopropanes with ethyl nitrite in the presence of sulfur trioxide and sulfur trioxide dioxane complex, as well as the reactions of 1-alkyl-2-arylcyclopropanes with NOBF4 were studied. It was found that the attack of the nitrosonium cation, accompanied by the formation of a benzyl carbocation, leads to the formation of isoxazolines. The introduction of bulky alkyl substituents into the cyclopropane ring changes the regioselectivity of nitrosation, favoring the attack of the electrophilic particle on the benzyl position and leading to the competitive formation of an alkyl carbocation. Depending on the structure of the alkyl substituent, both products of intramolecular heterocyclization accompanied by skeletal rearrangements and products formed with the participation of an external nucleophile are formed.
- Bondarenko, O. B.,Gavrilova, A. Yu.,Solodovnikova, T. A.,Tikhanushkina, V. N.,Zyk, N. V.
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p. 753 - 762
(2020/07/03)
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- In Situ Generation of Nitrile Oxides from NaCl-Oxone Oxidation of Various Aldoximes and Their 1,3-Dipolar Cycloaddition
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Reported is a new green protocol for the efficient in situ generation of nitrile oxides through NaCl/Oxone oxidation of aldoximes and their dipolar cycloaddition. The key feature is the use of a green chemistry approach to address the substrate scope of aldoximes: broad scope (aliphatic, aromatic, and alkenyl aldoximes) without production of organic byproducts derived from oxidant and/or catalyst. Importantly, NaCl/Oxone-promoted three-component cycloaddition of aldehyde, hydroxylamine hydrochloride, and alkene was demonstrated to be competent (63-81%).
- Zhao, Guodong,Liang, Lixin,Wen, Chi Ho Ethan,Tong, Rongbiao
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supporting information
p. 315 - 319
(2019/01/08)
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- PhIO promoted synthesis of nitrile imines and nitrile oxides within a micellar core in aqueous media: A regiocontrolled approach to synthesizing densely functionalized pyrazole and isoxazoline derivatives
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A highly efficient and general protocol has been developed for the facile synthesis of highly diversified 1,3,5-trisubstituted pyrazoles and 3,5-disubstituted 2-isoxazolines through one-pot tandem intermolecular, as well as intramolecular, dipolar [3 + 2] cycloaddition reactions. Chemoselective oxidation of aldohydrazone to nitrile imine and aldoximes to nitrile oxides by iodosobenzene in neutral aqueous media was performed. The scope of the reactions in regiocontrolled dipolar cycloaddition with olefins in the presence of PhIO toward highly substituted pyrazole and isoxazoline derivatives has been demonstrated. SDS converted the initially floating reaction mass and the organo-oxidant PhIO into a homogeneous mixture, which on stirring became a turbid emulsion. The micellar arrangement was confirmed by dynamic light scattering and optical microscopy. The new, green and metal free synthetic method enabled the execution of regiocontrolled tandem cycloaddition oxidation sequences leading to a library of pyrazole and isoxazoline derivatives.
- Pal, Gargi,Paul, Sanjay,Ghosh, Partha Pratim,Das, Asish R.
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p. 8300 - 8307
(2014/02/14)
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- KF/Al2O3: Solid-supported reagent used in 1,3-dipolar cycloaddition reaction of nitrile oxide
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The stereoselective synthesis of 2-isoxazolidine through 1,3-dipolar cycloaddition reaction of nitrile oxide, which is in situ generation from aldoxime in the presence of N-bromosuccinamide and solid-supported reagent KF/Al2O3 at room temperature, is reported. KF/Al2O3 is sufficiently basic such that it can replace organic bases such as Et 3N used in typical procedures and it catalyses the reaction to enhance the rate of the reaction.
- Boruah, Monalisa,Konwar, Dilip
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experimental part
p. 3261 - 3268
(2012/09/11)
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- New aspects of nitrosation of arylcyclopropanes: Nitrosation of phenylcyclopropanes with bulky alkyl substituents in the small ring
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It has been shown for the first time that nitrosation of phenylcyclopropanes with bulky alkyl substituents in the small ring proceeds predominantly with attack of the nitrosonium cation on the benzyl carbon atom of the cyclopropane ring with intermediate
- Bondarenko,Gavrilova,Saginova,Zyk,Zefirov
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experimental part
p. 1275 - 1283
(2009/06/05)
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- Synthesis of hydroximoyl chlorides from aldoximes and benzyltrimethylammonium tetrachloroiodate (BTMA ICl4)
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Benzyltrimethylammonium tetrachloroiodate (BTMA ICl4) acts as a convenient reagent to convert aldoximes to hydroximoyl chlorides by a simple procedure. When an aldoxime is treated with BTMA ICl4 in dichloromethane, the suspension of BTMA ICl4 shortly disappears as the reaction proceeds. The resulting BTMA ICl2 can be precipitated out by adding diethyl ether. Not only stable aromatic and heteroaromatic hydroximoyl chlorides can be isolated by this method but also rather unstable aliphatic hydroximoyl chlorides can be generated in situ. 1,3-Dipole trapping with a dipolarophile is performed in one flask and in some cases the chlorination is successfully performed in the presence of dipolarophile and triethylamine. Effect of MS 4A has been examined. (C) 2000 Elsevier Science Ltd.
- Kanemasa, Shuji,Matsuda, Haruhiko,Kamimura, Akio,Kakinami, Takaaki
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p. 1057 - 1064
(2007/10/03)
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- 154. Asymmetric synthesis of 3-hydroxyprolines by photocyclization of C(1′)-substituted N-(2-benzoylethyl)glycine esters
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The chiral N-(2-benzoylethyl)-N-tosylglycine esters 5a-h and the α -amino-γ-keto ester 6 were prepared from γ-(tosylamino) alcohols 7a-h. Irradiation of compounds 5a-c, e gave cis-3-hydroxyproline esters 20-23 (Scheme 6), partly with complete asymmetric induction by the C(1′)-substituent, whereas 6 gave enantiomerically pure 4-hydroxy-4-phenyl-L-proline esters 24 in good yield but low de (Scheme 6). The de of the photocyclization depended on the nature and/or size of the C(1′)-substituents. Irradiation of ketones 5d and 5f, bearing H-atoms at C(γ) with respect to the keto function, gave cyclobutanols (Scheme 9) in low yields besides the preferred Norrish-type-II cleavage product. Cyclopentanol 25 was a by-product of the photocyclization of 5c as a result of H-C(δ) abstraction from the t-Bu group The structure of products 20, 22, and 24a, b was established by NMR or X-ray analyses.
- Steiner, Andre,Wessig, Pablo,Polborn, Kurt
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p. 1843 - 1862
(2007/10/03)
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