Enantioselective Norrish–Yang Cyclization Reactions of N-(ω-Oxo- ω-phenylalkyl)-Substituted Imidazolidinones in Solution and in the Solid State
作者:Thorsten Bach、Tobias Aechtner、Bernhard Neumüller
DOI:10.1002/1521-3765(20020603)8:11<2464::aid-chem2464>3.0.co;2-s
日期:2002.6.3
single-crystal X-ray crystallography of its chiral N-methoxyphenylacetyl derivative 15a. In a similar fashion, the absolute configurations of the endo products 12b and ent-12b were established. The N-2-oxoethylimidazolidinone 5, which crystallized in a chiral space group, was irradiated in the solid state. At low levels of conversion, the product 9a/ent-9a was formed with high enantiomeric excess (78%
由N-乙酰基咪唑啉酮(4)制备四个N-(ω-氧代-ω-苯基-烷基)-取代的咪唑啉酮5-8。辐照后,这些底物经历了Norrish-Yang环化反应,形成外消旋产物rac-9-rac-12(51-75%)。N-2-氧代乙基咪唑啉酮5和6的反应在tBuOH中进行,生成1:1的exo / endo非对映异构体rac-9a / rac-9b和rac-10a / rac-10b的混合物,伴随着Norrish II型裂解产品。N-3-氧丙基咪唑啉酮7和8的反应在甲苯中进行。外非对映异构体rac-11a和rac-12a是主要的非对映异构体(dr大约等于4:1)。在手性化合物1-3的存在下,底物8的光环化以显着的对映体过量(5-60%ee)进行。比内酰胺1和2(最高ee为26%),更复杂的络合剂3和ent-3提供更好的对面分化(最高ee为60%)。低温和过量的络合剂有助于提高对映选择性。通过配合物3的手性N