Methylenecyclopropane Rearrangement as a Probe for Free Radical Substituent Effects. σ <sup>•</sup> Values for Potent Radical-Stabilizing Nitrogen-Containing Substituents
作者:Xavier Creary、Paul S. Engel、Natasha Kavaluskas、Li Pan、Allison Wolf
DOI:10.1021/jo990732d
日期:1999.7.1
used to calculate sigma (*) values, which are a measure of the radical stabilizing ability of the substituent. Groups such as p-N=N-Bu-t, p-CH=N-Bu-t, p-NH(2), p-CH=N-OH, and p-CH=N-OCH(3), are "good" radical stabilizers. We have also classified groups such as p-CH=N-NMe(2), p-N=N-Ph, p-N=N(O)-Bu-t, p-CH=N(O)-Bu-t, and p-CH=N-O(-) M(+), which have an extraordinarily large radical stabilizing effect
已经制备了一系列含氮的2-芳基-3,3-二甲基亚甲基环丙烷,并且已经测量了对相应的2-芳基异亚丙基亚环丙烷的重排速率。这些速率取决于芳基对位的含氮基团的性质。重排速率已用于计算σ(*)值,该值是取代基的自由基稳定能力的度量。pN = N-Bu-t,p-CH = N-Bu-t,p-NH(2),p-CH = N-OH和p-CH = N-OCH(3)等基团是“好”的自由基稳定剂。我们还对诸如p-CH = N-NMe(2),pN = N-Ph,pN = N(O)-Bu-t,p-CH = N(O)-Bu-t和p等进行了分类作为“超级稳定剂”,具有特别大的自由基稳定作用的-CH = NO(-)M(+)。这些取代基通过广泛的自旋离域作用稳定了亚甲基环丙烷重排的过渡态。在后三个取代基的情况下,提出了硝酰基型稳定化。对一系列含氮取代的苄基进行了密度泛函计算(B3LYP / 6-31G)。亚甲基环丙烷重排的速