Solid-state photochemistry of crystalline pyrazolines: reliable generation and reactivity control of 1,3-biradicals and their potential for the green chemistry synthesis of substituted cyclopropanes
作者:Saori Shiraki、Cortnie S. Vogelsberg、Miguel A. Garcia-Garibay
DOI:10.1039/c2pp25263e
日期:2012.12
To expand on the limited number of examples that exist in the literature for the solid-state photodenitrogenation of azoalkanes, a series of crystalline 7-alkyl-2,3,7-triazabicyclo[3.3.0]oct-2-ene-6,8-diones with varying 4,4-substituents were prepared. Their photochemical behavior in solution and in the solid state was dependent on the 4,4-substitution of the 1-pyrazoline ring, with unsubstituted pyrazoline 12 giving a mixture of products both in solution and in the solid state. Diphenyl substituted pyrazolines 13 denitrogenate spontaneously in solution but require light exposure to react quantitatively in the solid state. t-Butyl-phenyl substituted pyrazolines 14 were shown to denitrogenate both chemo- and diastereoselectively in solution and in the solid state to yield a single product in quantitative yield.
为了扩展文献中关于偶氮烷烃固态光脱氮反应的有限实例,我们制备了一系列具有不同4,4-取代基的7-烷基-2,3,7-三氮杂双环[3.3.0]辛-2-烯-6,8-二酮晶体。它们在溶液和固态下的光化学行为取决于1-吡唑啉环的4,4-取代基,未取代的吡唑啉12在溶液和固态下都会产生混合产物。二苯基取代吡唑啉13在溶液中自发脱氮,但在固态下需要光照才能定量反应。叔丁基苯基取代吡唑啉14在溶液和固态下均表现出化学和立体选择性脱氮,以定量产率产生单一产物。