A comparative mechanistic analysis of the stereoselectivity trends observed in the oxidation of chiral oxazolidinone-functionalized enecarbamates by singlet oxygen, ozone, and triazolinedione
作者:J. Sivaguru、Thomas Poon、Catherine Hooper、Hideaki Saito、Marissa R. Solomon、Steffen Jockusch、Waldemar Adam、Yoshihisa Inoue、Nicholas J. Turro
DOI:10.1016/j.tet.2006.07.105
日期:2006.11
stereoselectivity, substantially dependent on solvent and temperature, is displayed for the reactions with 1O2, whereas the ground-state reactants O3 and PTAD are rather unaffected by solvent and temperature variations. The present comparative analysis clearly substantiates our hypothesis of stereoselective vibrational quenching of the attacking 1O2, whereas O3 and PTAD are only subject to steric impositions. The
配备了恶唑烷酮手性助剂的E / Z氨基甲酸酯1在反应中的立体选择性已针对单线态氧(1 O 2),臭氧(O 3)和4-苯基-1,2,4-三唑啉进行了检测。 -3,5-二酮(PTAD)在各种溶剂中随温度的变化而变化。烯基官能度被1 O 2和O 3氧化裂解,释放出对映异构体富集的甲基脱氧安息香(MDB)产物。的程度(%ee),为以及所述感测(ř VS小号MDB形成中的立体选择性取决于氧化剂的电子性质。对于与1 O 2的反应,显示出基本上取决于溶剂和温度的高立体选择性,而基态反应物O 3和PTAD几乎不受溶剂和温度变化的影响。目前的比较分析清楚地证实了我们对进攻的1 O 2的立体选择性振动淬灭的假设,而O 3和PTAD仅受到空间位点的影响。电子激发1 O 2是体现在手性enecarbamates,所有这三个立体化学相关的结构特性敏感即- [R /小号配置在C 4的恶唑烷酮手性辅助剂,所述的位置Ž /