Homolytic aziridine opening (aza variant of cyclopropylcarbinyl-homoallyl rearrangement) by addition of tributyltin radical to N-acylaziridines. Factors contributing to the regioselectivity
作者:Jürgen Werrya、Helmut Stamm、Pen-Yuan Lin、Reinhard Falkenstein、Stefan Gries、Hermann Irngartinger
DOI:10.1016/s0040-4020(01)81081-4
日期:1989.1
fell drastically with steric hindrance of the addition of Bu3Sn. to the acyl oxygen of 1. They depended to some extent on the experimental conditions for hydrogen capturing when aziridine homolysis provided a primary radical 3 or 6. The regioselectivity of (probably reversible) ring homolysis can be understood in terms of the stability of the arising radical (3, 6), of stereoelectronic control (e.g. 1i
AIBN在回流的苯中引发N-酰基丙啶1与Bu 3 SnH的反应,提供了还原性开环的产物5和8。由于添加了Bu 3 Sn的位阻,产率(大多数情况下是定量的)急剧下降。到1的酰基氧。他们在一定程度上取决于当氮丙啶均质分解提供伯自由基3或6时捕获氢的实验条件。的(可能是可逆的)环均裂区域选择性可以的产生自由基(稳定性的观点出发可以理解3,6),立体声电子控制(例如1i与1h相比)和边界轨道相互作用(1j)。从1j形成一级自由基的解释中,键长可能存在差异,但从N-甲苯磺酰基-2-甲基-氮丙啶11的X射线结构分析中未发现支持。异构体产物仅获得两次(1i,1j),比率5j:8j取决于Bu 3 SnH的浓度和氢同位素。没有发现比例为5:14的这种依赖关系(环化和无环化时减少3)由N-肉桂酰基氮丙啶11得到的吡咯烷酮。该比率(1:9为11和1:3为1N)必须反映在EZ异构体3。所观察到的由2形成E-3的偏