Atropisomerism in Amidinoquinoxaline <i>N-</i>Oxides: Effect of the Ring Size and Substituents on the Enantiomerization Barriers
作者:Jimena E. Díaz、Nicolas Vanthuyne、Hélène Rispaud、Christian Roussel、Daniel Vega、Liliana R. Orelli
DOI:10.1021/jo502626f
日期:2015.2.6
support. A clear ring size effect was evidenced. In all cases, six-membered amidine derivatives 1 showed higher barriers than the corresponding lower homologues 2, which also display lower sensitivity to the substituent size. Transition states for the interconversion of the atropisomers were located using DFT calculations, and involved the interaction of the ortho substituent with the formally sp2 nitrogen
新型的带有不对称(邻位取代)5-芳基残基的2,3-二氢-1 H-嘧啶并[1,2 - a ]喹喔啉6-氧化物1和同源的1,2-二氢咪唑并[1,2-研究了α ]喹喔啉5-氧化物2。已证明化合物1a存在手性轴通过X射线衍射和基态几何的DFT计算。阻转异构体对映体在手性固定相上的拆分得到了报道。通过离线外消旋研究和/或在手性支持物色谱过程中通过处理平台形色谱图来确定对映异构化的障碍。明显的环尺寸效应被证明。在所有情况下,六元am衍生物1都比相应的较低同系物2表现出更高的势垒,后者对取代基的大小也表现出较低的敏感性。通过DFT计算确定了对映异构体互变的过渡态,并涉及邻位取代基与形式为sp 2的相互作用部分中的氮。相反,在2-硝基衍生物的最有利的对映异构转变状态下,邻位取代基接近于N-氧化物基团。