The nitrile oxide–isocyanate rearrangement

Taylor, Giles A.

doi:10.1039/p19850001181

Cited by 16 publications

(10 citation statements)

References 1 publication

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“…ESI-MS: m / z 556 [M] − . The 10% 18 O-labeled (PPh 4 )[Os III {NHCNH 2 (NH 18 OH)}( L )(CN) 3 ] was obtained using 10% 18 O-labeled NH 2 18 OH·HCl . ESI-MS: m / z 555 [M] − .…”

Section: Methodsmentioning

confidence: 99%

Aerobic Oxidation of an Osmium(III) N-Hydroxyguanidine Complex To Give Nitric Oxide

et al. 2016

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The aerobic oxidation of the N-hydroxyguanidinum moiety of N-hydroxyarginine to NO is a key step in the biosynthesis of NO by the enzyme nitric oxide synthase (NOS). So far, there is no chemical system that can efficiently carry out similar aerobic oxidation to give NO. We report here the synthesis and X-ray crystal structure of an osmium(III) N-hydroxyguanidine complex, mer-[Os(III){NH═C(NH2)(NHOH)}(L)(CN)3](-) (OsGOH, HL = 2-(2-hydroxyphenyl)benzoxazole), which to the best of our knowledge is the first example of a transition metal N-hydroxyguanidine complex. More significantly, this complex readily undergoes aerobic oxidation at ambient conditions to generate NO. The oxidation is pH-dependent; at pH 6.8, fac-[Os(NO)(L)(CN)3](-) is formed in which the NO produced is bound to the osmium center. On the other hand, at pH 12, aerobic oxidation of OsGOH results in the formation of the ureato complex [Os(III)(NHCONH2)(L)(CN)3](2-) and free NO. Mechanisms for this aerobic oxidation at different pH values are proposed.

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“…ESI-MS: m / z 556 [M] − . The 10% 18 O-labeled (PPh 4 )[Os III {NHCNH 2 (NH 18 OH)}( L )(CN) 3 ] was obtained using 10% 18 O-labeled NH 2 18 OH·HCl . ESI-MS: m / z 555 [M] − .…”

Section: Methodsmentioning

confidence: 99%

Aerobic Oxidation of an Osmium(III) N-Hydroxyguanidine Complex To Give Nitric Oxide

et al. 2016

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“…25 We therefore favour a mechanism involving an equilibrium between SO 2 /RCNO and dioxathiazole S-oxide 15 and its subsequent fragmentation at O(1)−S(2) and O(3)−N(4) with concomitant C→N migration of the R-group (Scheme 4, path B). Isocyanate formation via Path B is also supported by studies 26 using 18 O-labelled mesitonitrile oxide (2, R = 2,4,6-Me 3 C 6 H 2 ) when the 18 O label was detected in the recovered sulfur dioxide. A similar approach can be used to convert nitrile oxides into isothiocyanates.…”

mentioning

confidence: 56%

Flash vacuum pyrolysis of 1,2,5-oxadiazole 2-oxides and 1,2,3-triazole 1-oxides

Mitchell¹,

Paton²

2010

Arkivoc

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The flash vacuum pyrolysis (FVP, 450-600 ºC/10 -3 mmHg) of 3,4-diaryl-and 3,4-dialkyl-1,2,5-oxadiazole 2-oxides (furoxans) has been investigated. In all cases the 1,2,5-oxadiazole ring cleaved cleanly at O(1)-N(2) and C(3)-C(4) to afford two nitrile oxide fragments, which were trapped in high yield (75-97%) as their isoxazoline cycloadducts by reaction with alk-1-enes. At higher temperatures (700-800 ºC) isocyanates were formed as by-products. The dimerisation of acetonitrile oxide to dimethylfuroxan was followed by 1 H NMR spectroscopy, and the rate constant for the 2 nd order reaction determined. The furoxans were converted into isocyanates in good yield (61-95%) by FVP, followed by sulfur dioxide-mediated isomerisation of the resulting nitrile oxides. 2,4,5-Trisubstituted-1,2,3-triazole 1-oxides showed greater thermal stability, but at 700-800 ºC decomposition of the 4,5-dimethyl compound 25b lead to 1,2-di(5-methyl-2-phenyl-1,2,3-triazol-2-yl)ethane as the major product; attempts to trap acetonitrile oxide were unsuccessful.

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“…The mechanism via the [3+2] cycloaddition included four pathways because of the four different additive patterns. (c) The bimolecular isomerization via the [3+3] cycloaddition ( Path I ) was previously proposed …”

Section: Resultsmentioning

confidence: 99%

“…The bimolecular isomerization of nitrile N ‐oxide to isocyanates via [3+3] cycloadditive dimerization has been previously proposed; however, it was not evaluated through theoretical calculation. The dimerization of nitrile N ‐oxide to furoxane was investigated by Houk and co‐workers using theoretical calculations .…”

Section: Introductionmentioning

confidence: 99%

Exploration of Unimolecular and Bimolecular Pathways for Nitrile N‐Oxide Isomerization to Isocyanate Through Global Reaction Route Mapping Techniques

et al. 2019

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Mechanisms of the unimolecular and bimolecular isomerization of nitrile N‐oxide to isocyanate were investigated by quantum chemical calculations using the global reaction route mapping (GRRM) technique, which consists of the anharmonic downward distortion following (ADDF) and multi‐component artificial force induced reaction (AFIR) methods, which can exhaustively search reaction paths. In the unimolecular isomerization, isomerization paths of nitrile N‐oxide to isocyanate were exhaustively explored by the ADDF method. The energetically lowest path for 2,6‐dimethoxybenzonitrile oxide (Ar–CNO) isomerization was via oxazirine intermediate formation, which was the rate‐determining step with an activation free energy of 56.8 kcal mol–1. The high activation free energy indicates that the isomerization hardly proceeds as a thermal unimolecular reaction. Next, the bimolecular isomerization paths of Ar–CNO were explored for diradical addition, [3+2] and [3+3] cycloadditions, and self‐catalyzed isomerization through the AFIR method. The diradical addition was the energetically lowest path with an activation free energy of 55.4 kcal mol–1. Although the bimolecular isomerization was energetically favorable than the unimolecular isomerization, its activation free energy was still high for the reaction to proceed under thermal conditions. Exhaustive path searching for these unimolecular and bimolecular isomerizations suggest that these reactions are catalyzed by acid or base.

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The nitrile oxide–isocyanate rearrangement

Cited by 16 publications

References 1 publication

Aerobic Oxidation of an Osmium(III) N-Hydroxyguanidine Complex To Give Nitric Oxide

Aerobic Oxidation of an Osmium(III) N-Hydroxyguanidine Complex To Give Nitric Oxide

Flash vacuum pyrolysis of 1,2,5-oxadiazole 2-oxides and 1,2,3-triazole 1-oxides

Exploration of Unimolecular and Bimolecular Pathways for Nitrile N‐Oxide Isomerization to Isocyanate Through Global Reaction Route Mapping Techniques

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