Ruane Patrick H, Bushan K Mani, Pavlos Christopher M, D'Sa Raechelle A, Toscano John P
Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
J Am Chem Soc. 2002 Aug 21;124(33):9806-11. doi: 10.1021/ja026900s.
An investigation of potential photosensitive protecting groups for diazeniumdiolates (R2N-N(O)=NO-) has been initiated, and here the effect of meta electron-donating groups on the photochemistry of O2-benzyl-substituted diazeniumdiolates (R2N-N(O)=NOCH2Ar) is reported. Photolysis of the parent benzyl derivative (Ar = Ph) results almost exclusively in undesired photochemistry-the formation of nitrosamine and an oxynitrene intermediate with very little, if any, photorelease of the diazeniumdiolate. We have been able to use meta substitution to tune the photochemistry of these benzylic systems. The desired diazeniumdiolate photorelease has been shown to become more substantial with stronger pi-donating meta substituents. This effect has been verified by direct observation of the photoreleased diazeniumdiolate with 1H NMR spectroscopy and by NO quantification measurements conducted in high- and low-pH solutions. In addition, the observed rates of NO release are consistent with that expected for normal thermal decomposition of the diazeniumdiolate in aqueous solutions and also show the same pH dependence.
已开始对重氮二醇盐（R2N-N(O)=NO-）的潜在光敏保护基团进行研究，本文报道了间位给电子基团对O2-苄基取代的重氮二醇盐（R2N-N(O)=NOCH2Ar）光化学性质的影响。母体苄基衍生物（Ar = Ph）的光解几乎完全导致不期望的光化学反应——亚硝胺和氧氮烯中间体的形成，而重氮二醇盐的光释放极少，甚至没有。我们能够利用间位取代来调节这些苄基体系的光化学性质。已表明，随着给电子能力更强的间位取代基的存在，所需的重氮二醇盐光释放变得更加显著。通过1H NMR光谱直接观察光释放的重氮二醇盐以及在高pH和低pH溶液中进行的NO定量测量，验证了这一效应。此外，观察到的NO释放速率与重氮二醇盐在水溶液中正常热分解预期的速率一致，并且也显示出相同的pH依赖性。
