Stabile 4<i>H</i>‐1,2‐Oxazete durch intramolekulare Cyclisierung α,β‐ungesättigter Nitrosoverbindungen

Wieser, Karlheinz; Berndt, A.

doi:10.1002/ange.19750870212

Cited by 16 publications

(3 citation statements)

References 11 publications

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“…10) can decompose by two pathways (Scheme 4, with the relative energies given at structures and reaction barriers, at arrows; values in kJ mol !1 ). The first pathway involves isomerization (28) into compound XX with the half-chair conformation, followed by formation of a five-membered ring [XXII, reaction (30)], nitro3nitrite rearrangement [XXIII, reaction (31)], and elimination of HNO 2 [reaction (32)]. The second pathway via biradical XXI is more energetically favorable according to the available data.…”

Section: ääääääääääääääääääääääääáääääääääääääääääáäääääääääääääääáäämentioning

confidence: 93%

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Mechanism of gas-phase decomposition of nitroethylene: A theoretical study

2004

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Calculations by the B3LYP density functional method with various basis sets and by the QCISD(T)/6-31G(d) ab initio method showed that the main pathway of monomolecular gas-phase decomposition of nitroethylene is that involving a cyclic intermediate, 4H-1,2-oxazete 2-oxide; the barrier of its formation (201.9, 203.9, and 216.5 kJ mol !1 , as estimated by various methods) reasonably agrees with the experimental value (191.9 kJ mol !1 ). The barriers of alternative pathways of gas-phase decomposition of nitroethylene are considerably higher. The barriers of reactions involving radical cations are considerably lower than those of the similar reactions involving molecules. Among all the considered pathways of nitroethylene decomposition, bimolecular pathways are the most favorable energetically.Two major pathways of gas-phase decomposition of aliphatic nitro compounds have been proved experimentally: homolytic cleavage of the C3N bond with generation of free radicals and elimination of HNO 2 [13 4]. The molecular mechanism is realized at relatively low temperatures (up to 350oC) with mononitroalkanes containing a hydrogen atom in the a position relative to the nitro group, and also with halonitroalkanes RCH 2 CHXNO 2 (X = Hlg) [2, 3]. Gasphase decomposition of nitroethylene I and other a-nitroolefins is presumed to occur by a similar mechanism [2, 3, 5]. For mononitroalkanes, the molecular mechanism of HNO 2 elimination is confirmed by data on the composition of products in the initial steps of decomposition [1,2] and by the results of quantumchemical calculations [6 38]. Data on the composition of products formed in the initial steps of decomposition of I are lacking; therefore, the molecular mechanism for this compound is just a hypothesis. Published results of quantum-chemical studies of nitroethylene decomposition [9,10] are apparently insufficient to make any definite conclusions on the primary step of the monomolecular gas-phase decomposition or to cast doubt on the suggested pathway of HNO 2 elimination. In [11,12], we found that the barrier to elimination of HNO 2 from a molecule of I [223.9 kJ mol !1 according to B3LYP/6-311++G(df,p) calculations] significantly exceeds the experimental activation energy of the gas-phase decomposition (191.9 kJ mol !1 ).In this work, we studied theoretically various alternative pathways of monomolecular decomposition of

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Section: ääääääääääääääääääääääääáääääääääääääääääáäääääääääääääääáäämentioning

confidence: 93%

“…Although formation of VII in thermal decomposition of nitroethylene was not proved experimentally, related oxazetes were prepared by cyclization of substituted nitroethylenes [29,30].…”

Section: Radical Decompositionmentioning

confidence: 99%

Mechanism of gas-phase decomposition of nitroethylene: A theoretical study

2004

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“…Then, single-electron oxidation of enamine intermediate 7 occurs to provide radical cation F, which can be further trapped by NO radicals to afford iminium ion G. Then, deprotonation is preferred followed by cyclization to form the four-membered ring I. 56,57 The ring-opening…”

Section: Potential Application In the Synthesis Of Bioactive Moleculesmentioning

confidence: 99%

Chemoselective Nitrosylation of Anilines and Alkynes via Fragmentary or Complete NO Incorporation

Pan

Lin

et al. 2018

Chem

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The cycloaddition reactions have been explored extensively and provided an efficient strategy for the synthesis of cyclic compounds. Traditionally, the reaction partners were in extenso incorporated into the cyclic products without fragmentation. From a different perspective, if certain fragmentations via chemical-bond cleavage are involved in this cycloaddition reaction, it would change the assembly sequence and enable more product diversity. Here, we report a chemoselective nitrosylation of anilines and alkynes through fragmentary or complete NO radical incorporation. The formation of multiple C-N bonds, an unexpected C-N bond, and N=O bond cleavage make this fragmentary cycloaddition reaction an efficient approach to 2,5-dihydrooxazoles, 1H-1,2,3-triazole 2-oxides or quinoxaline N-oxides. Facile operation in open-air, metal-free, and mild conditions renders this protocol particularly practical and attractive. A series of mechanistic studies and density functional theory calculations were also conducted, which help to explain the fragmentary or complete NO incorporation processes, broadening the field of new reaction discovery.

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