Generation,Characterization And Chemical Reactions Of Sulfonyl Nitrenes

As a class of important reactive intermediates,sulfonyl nitrenes have been widely used in chemistry,biology and materials,and its generation,structure,electronic configuration and chemical reactivity are one of the hot topics in the field of physical organic chemistry.However,nitrenes are usually very active at room temperature,the lifetime of nitrene very short,making the research on direct in situ spectroscopic detection of nitrene difficult.As an important type of?-oxo nitrenes,the generation,structure and chemical reactions of sulfonyl nitrenes have been paid close attention,and have certain guiding significance for the research of other?-oxo nitrenes.In this thesis,the methoxysulfonyl nitrene,benzenesulfonyl nitrene and methanesulfonyl nitrene were studied using the low temperature synthesis,matrix isolation IR spectroscopy,high flash vacuum pyrolysis and quantum chemical calculations.Systematic and comprehensive studies of their IR spectra,molecular structures and chemical reaction mechanisms have been carried out.The main work of this thesis includes the following three aspects.1.The simplest N-sulfonylamine HNSO₂ has been generated in the gas phase through flash vacuum pyrolysis of methoxysulfonyl azide CH₃OS?O?₂N₃.Its identification was accomplished by combining matrix-isolation IR spectroscopy and quantum chemical calculations.Both experimental and theoretical evidences suggest a stepwise decomposition of the azide via the methoxysulfonyl nitrene CH₃OS?O?₂N,observed in the 193 nm laser photolysis of the azide,with concerted fragmentation into HCHO and HNSO₂,and no pseudo-Curtius rearrangement product CH₃ONSO₂genenated.Upon the 193 nm laser irradiation,HNSO₂ isomerizes into the novel N-hydroxysulfinylamine HONSO.This work not only provides a method to generate the HNSO₂ but also a potential access to the anion NSO₂^-.2.The thermal-and photo-decomposition of benzenesulfonyl azide,PhS?O?₂N₃,has been studied by combining matrix-isolation IR spectroscopy and quantum chemical calculations.Upon flash vacuum pyrolysis at 800 K,the azide splits off molecular nitrogen and exclusively furnishes phenylnitrene?PhN?,SO₂ and N₂ in the gas phase.In contrast,the azide favors stepwise photodecomposition in solid Ar and Ne matrices at2.8 K.Specifically,the UV laser photolysis?l=193 and 266 nm?of the PhS?O?₂N₃results in the formation of the key nitrene intermediate PhS?O?₂N in the triplet ground state,which undergoes pseudo-Curtius rearrangement into N-sulfonyl imine PhNSO₂under the subsequent visible light irradiation?l=380–450 nm?.Further fragmentation of PhNSO₂ into SO₂ and didehydroazepine?cyclic C₆H₅N?also occurs upon the visible light irradiation.The preference of the stepwise mechanism for the decomposition of PhS?O?₂N₃ is supported by the quantum chemical calculations with DFT B3LYP/6-311++G?3df,3pd?and CBS-QB3 methods.3.The parent sulfonyl azide CH₃S?O?₂N₃ has been fully characterized in a neat form by IR?gas,matrix-isolation?and Raman?solid?spectroscopy,and its structure has been established by X-ray crystallography.In both gas phase and solid state,the azide exhibits single conformation with the azido ligand being synperiplanar to one of the two S=O groups.In the crystal molecules of CH₃S?O?₂N₃ are interconnected through three-dimensional O···H-C-H···O hydrogen bonds.Upon an ArF laser?l=193 nm?photolysis,the azide in solid noble gas matrices splits off N₂ and yields the sulfonyl nitrene CH₃S?O?₂N in the triplet ground state.Subsequent photolysis with UV light?l=266 nm?causes the transformation from the nitrene to the pseudo-Curtius rearrangement product CH₃NSO₂.The identification of the photolysis intermediates by matrix isolation IR spectroscopy is supported by quantum chemical calculations with DFT methods.