Acylated 2,2-dimethylaziridines: regioselectivity of ring opening by sodium thiophenolate; borderline SN2 due to planarization of nitrogen pyramid
作者:Pen-yuan Lin、Konstantinos Bellos、Helmut Stamm、Andreas Onistschenko
DOI:10.1016/s0040-4020(01)88757-3
日期:1992.3
carrying a COR group on nitrogen are opened by PhS⊖ with a regioselectivity RS = abnormal:normal ⩾ 20 in MeOH and 5–16 in THF. Practically no influence of COR on RS was found except for the poorest oxidant 1g (R = tBu) that gave the highest RS (95, MeOH). This rules out an SET mechanism for the abnormal opening. Absence of homolytic ring opening is directly shown by the failure to detect products resulting
2,2- Dimethylaziridines 1正常⩾20在MeOH和5-16在THF:承载上氮COR基团通过PhS⊖具有区域选择性RS =异常打开。几乎没有发现COR对RS的影响,除了最差的氧化剂1g(R = tBu)给出了最高的RS(95,MeOH)。这排除了用于异常打开的SET机制。当COR为肉桂酰基(1f)时,没有检测到由均溶形成的自由基环化产生的产物,可以直接证明没有均溶的开环。当位阻增加时(N-苯甲酰基氮丙啶13),任何与PhS 6的反应的抑制都表明了直接的亲核攻击。观察到的S N 2的边界行为为1通过反应不良的1的扁平氮构型的反应来解释。在这种(几乎)平面构象中的羧酰胺共振在N上产生大量正电荷,通过在被PhS 4攻击之前,N-CMe 2键的部分杂化,该机理将更接近S N 1 。