Mieres-Pérez Joel, Mendez-Vega Enrique, Velappan Kavitha, Sander Wolfram
Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum , D-44780 Bochum, Germany.
J Org Chem. 2015 Dec 18;80(24):11926-31. doi: 10.1021/acs.joc.5b01263. Epub 2015 Nov 17.
Triplet carbenes react with molecular oxygen with rates that approach diffusion control to carbonyl O-oxides, whereas triplet nitrenes react much slower. For investigating the reaction of phenylnitrene with O2, the nitrene was generated by flash vacuum thermolysis (FVT) of phenylazide and subsequently isolated in O2-doped matrices. FVT of the azide produces the nitrene in high yield and with only minor contaminations of the rearranged products that are frequently observed if the nitrene is produced by photolysis. The phenylnitrene was isolated in solid Ar, Xe, mixtures of these rare gases with O2, and even in pure solid O2. At temperatures between 30 and 35 K an extremely slow thermal reaction between the nitrene and O2 was observed, whereas at higher temperatures, solid Ar and O2 rapidly evaporate. Only O2-doped Xe matrices allowed us to anneal at temperatures above 40 K, and at these temperatures, the nitrene reacts with O2 to produce nitroso O-oxide mainly in its syn conformation. Upon visible light irradiation (450 nm), the nitroso oxide rapidly rearranges to nitrobenzene.
三线态卡宾与分子氧反应生成羰基氧氧化物的速率接近扩散控制，而三线态氮烯的反应则慢得多。为了研究苯氮烯与O₂的反应，通过苯叠氮的快速真空热解（FVT）生成氮烯，随后将其分离在掺杂O₂的基质中。叠氮化物的FVT以高产率生成氮烯，且只有少量重排产物污染，而如果通过光解生成氮烯，则经常会观察到重排产物。苯氮烯被分离在固体Ar、Xe、这些稀有气体与O₂的混合物中，甚至在纯固体O₂中。在30至35K的温度下，观察到氮烯与O₂之间发生极其缓慢的热反应，而在较高温度下，固体Ar和O₂会迅速蒸发。只有掺杂O₂的Xe基质允许我们在40K以上的温度下退火，在这些温度下，氮烯与O₂反应主要生成顺式构象的亚硝基氧氧化物。在可见光（450nm）照射下，亚硝基氧化物迅速重排为硝基苯。
