Editing Nitrene (section)

==Reactions==
Nitrene reactions include:
* '''Nitrene C–H insertion'''. A nitrene can easily insert into a carbon to hydrogen [[covalent bond]] yielding an amine or amide. A singlet nitrene reacts with [[retention of configuration]]. In one study<ref>{{cite journal|title=Intermolecular Amidation of Unactivated sp<sup>2</sup> and sp<sup>3</sup> C–H Bonds via Palladium-Catalyzed Cascade C–H Activation/Nitrene Insertion |first1=Hung-Yat |last1=Thu |first2=Wing-Yiu |last2=Yu |first3=Chi-Ming |last3=Che |journal=[[J. Am. Chem. Soc.]] |date=2006 |volume=128 |issue=28 |pages=9048–9049 |doi=10.1021/ja062856v|pmid=16834374 }}</ref> a nitrene, formed by oxidation of a [[carbamate]]  with [[potassium persulfate]], gives an [[insertion reaction]] into the [[palladium]] to nitrogen bond of the reaction product of [[palladium(II) acetate]] with [[pyridine|2-phenylpyridine]] to methyl ''N''-(2-pyridylphenyl)carbamate in a [[cascade reaction]]:

::[[File:NitreneAmidation2.png|400px|Nitrene amidation]]

:A nitrene intermediate is suspected in this C–H insertion involving an [[oxime]], [[acetic anhydride]] leading to an [[isoindole]]:<ref>{{cite journal|title=Novel Intramolecular Reactivity of Oximes: Synthesis of Cyclic and Spiro-Fused Imines |first1=Cécile G. |last1=Savarin |first2=Christiane |last2=Grisé |first3=Jerry A. |last3=Murry |first4=Robert A. |last4=Reamer |first5=David L. |last5=Hughes |journal=[[Org. Lett.]] |date=2007 |volume=9 |issue=6 |pages=981–983 |doi=10.1021/ol0630043|pmid=17319674 }}</ref>

::[[File:NitreneOximeReaction.png|400px|Synthesis of cyclic and spiro-fused imines]]

* '''Nitrene cycloaddition'''. With [[alkene]]s, nitrenes react to form [[aziridines]], very often with [[nitrenoid]] precursors such as nosyl- or tosyl-substituted [''N''-(phenylsulfonyl)imino]phenyliodinane (PhI=NNs or PhI=NTs respectively)) but the reaction is known to work directly with the [[Sulfonamide (chemistry)|sulfonamide]] in presence of a [[transition metal]] based [[catalyst]] such as [[copper]], [[palladium]], or [[gold]]:<ref>{{cite journal|title=Nitrene Transfer Reactions Catalyzed by Gold Complexes |first1=Zigang |last1=Li |first2=Xiangyu |last2=Ding |first3=Chuan |last3=He |journal=[[J. Org. Chem.]] |date=2006 |volume=71 |issue=16 |pages=5876–5880 |doi=10.1021/jo060016t|pmid=16872166 |s2cid=43641348 }}</ref><ref>{{cite journal|title=Development of the Copper-Catalyzed Olefin Aziridination Reaction |first1=David A. |last1=Evans |first2=Margaret M. |last2=Faul |first3=Mark T. |last3=Bilodeau |journal=[[J. Am. Chem. Soc.]] |date=1994 |volume=116 |issue=7 |pages=2742–2753 |doi=10.1021/ja00086a007|s2cid=55554519 }}</ref><ref>{{cite journal|title=Mechanistic Studies of Copper-Catalyzed Alkene Aziridination |first1=Peter |last1=Brandt |first2=Mikael J. |last2=Sodergren |first3=Pher G. |last3=Andersson |first4=Per-Ola |last4=Norrby |journal=[[J. Am. Chem. Soc.]] |date=2000 |volume=122 |issue=33 |pages=8013–8020|doi=10.1021/ja993246g|s2cid=98310736 }}</ref><ref>{{cite journal|title=Advances in Nitrogen Transfer Reactions Involving Aziridines |first1=Iain D. G. |last1=Watson |first2=Lily |last2=Yu |first3=Andrei K. |last3=Yudi |journal=[[Acc. Chem. Res.]] |date=2006 |volume=39 |issue=3 |pages=194–206 |doi=10.1021/ar050038m|pmid=16548508 }}</ref><ref>Reactants ''cis''-[[stilbene]] or ''trans''-stilbene, nitrene precursor ''p''-nitrosulfonamide or [[Nosylate|nosylamine]] which is oxidized by [[iodosobenzene diacetate]]. The gold catalyst is based on a [[terpyridine]] tridentate [[ligand]].</ref>

::[[File:NitreneTransferReactionsCatalyzedbyGoldComplexes.png|400px|Nitrene transfer reaction]]

:In most cases, however, [''N''-(''p''-nitrophenylsulfonyl)imino]phenyliodinane (PhI=NNs) is prepared separately as follows:

::[[File:Preparation of PhINNs.png|600px|Preparation of PhINNs]]

:Nitrene transfer takes place next:

::[[File:Copper catalyzed aziridination.png|600px|Nitrene transfer reaction]]

:In this particular reaction both the ''[[cis isomer|cis]]''-[[stilbene]] illustrated and the [[trans isomer|''trans'']] form (not depicted) result in the same ''trans''-aziridine product, suggesting a two-step [[reaction mechanism]]. The energy difference between triplet and singlet nitrenes can be very small in some cases, allowing [[Intersystem crossing|interconversion]] at room temperature. Triplet nitrenes are thermodynamically more stable but react stepwise allowing free rotation and thus producing a mixture of stereochemistry.<ref>{{cite book|title=Aziridines and Epoxides in Organic Synthesis |editor-first=Andrei K. |editor-last=Yudin |date=2007 |page=120 |isbn=978-3-527-31213-9}}</ref>
* '''Arylnitrene ring-expansion and ring-contraction''': Aryl nitrenes show ring expansion to 7-membered ring [[cumulene]]s, ring opening reactions and nitrile formations many times in complex reaction paths. For instance the azide '''2''' in the scheme below<ref name=Kvaskoff /> trapped in an [[argon]] [[Matrix Isolation|matrix]] at 20&nbsp;K on photolysis expels nitrogen to the triplet nitrene '''4''' (observed experimentally with [[electron spin resonance|ESR]] and [[ultraviolet-visible spectroscopy]]) which is in equilibrium with the ring-expansion product '''6'''.

:[[File:NitreneRingContraction.png|400px|Nitrene ring-expansion and ring-contraction]]

:The nitrene ultimately converts to the ring-opened [[nitrile]] '''5''' through the [[diradical]] intermediate '''7'''. In a high-temperature reaction, [[flash vacuum thermolysis|FVT]] at 500–600&nbsp;°C also yields the nitrile '''5''' in 65% yield.<ref>The [[quinazoline]] is prepared from the corresponding bromide and [[sodium azide]]. The azide is in equilibrium with the [[tetrazole]] '''3'''.</ref> Arylnitrene internalization in combination with carbon deletion strategies have been used for aromatic carbon-nitrogen swap to generate [[pyridines]] from phenyl azides.<ref name="Sundberg 1972">{{cite journal |last1=Sundberg |first1=Richard J. |last2=Suter |first2=Stuart R. |last3=Brenner |first3=Martin |title=Photolysis of 0-substituted aryl azides in diethylamine. Formation and autoxidation of 2-diethylamino-1H-azepine intermediates |journal=[[Journal of the American Chemical Society]] |date=1972 |volume=94 |issue=2 |pages=513–520 |doi=10.1021/ja00757a032}}</ref><ref name="Burns 2022">{{cite journal |last1=Patel |first1=Sajan C. |last2=Burns |first2=Noah Z. |title=Conversion of Aryl Azides to Aminopyridines |journal=[[Journal of the American Chemical Society]] |date=2022 |volume=144 |issue=39 |pages=17797–17802 |doi=10.1021/jacs.2c08464}}</ref><ref name="Levin 2023">{{cite journal |last1=Pearson |first1=Tyler J. |last2=Shimazumi |first2=Ryoma |last3=Driscoll |first3=Julia L. |last4=Dherange |first4=Balu D. |last5=Park |first5=Dong-Il |last6=Levin |first6=Mark D. |title=Aromatic nitrogen scanning by <i>ipso</i>-selective nitrene internalization |journal=[[Science_(journal)|Science]] |date=2023 |volume=381 |issue=6665 |pages=1474–1479 |doi=10.1126/science.adj5331|pmc=10910605 }}</ref>