Kinetics and mechanisms of nucleophilic displacements with heterocycles as leaving groups. Part 9. N-substituted 2,4,6-triphenylpyridiniums, 5,6-dihydro-2,4-diphenylbenzo[h]quinoliniums, and 5,6,8,9-tetrahydro-7-phenyldibenzo[c,h]acridiniums: kinetic rate variation with structure of the N-substituent
作者:Alan R. Katritzky、Kumars Sakizadeh、Yu Xiang Ou、Bratislav Jovanovic、Giuseppe Musumarra、Francesco P. Ballistreri、Roberto Crupi
DOI:10.1039/p29830001427
日期:——
order benzyl > methyl ≃ s-alkyl > continuous chain primary alkyl ≃ neopentyl. Comparisons with literature data involving other leaving groups, standardized by reference to the ethyl compound in each series, again show that groups larger than ethyl tend to react faster in series (1), (2), and especially (3) than expected, and methyl tends to react more slowly. Similar but smaller trends are found in literature
Ñ -N-烷基,Ñ -S-烷基,Ñ -烯丙基,和Ñ标题化合物的苄基衍生物与哌啶和其它亲核试剂反应,在清楚地可分离小号Ñ 1和/或小号ñ 2个反应。对于Ñ -s-三烷基化合物,小号Ñ 2率降低与亲核试剂亲核的,而小号Ñ 1速率是由亲核试剂的性质的影响。该小号Ñ 1反应显示出比找到符合更高的激活熵小号Ñ 2反应。尽管对于相同的N-取代基,SN 2比率始终以(1)<(2)<(3)的顺序增加,比率增强对于不同的N-取代基有很大变化:这些变化可以通过N-取代基的空间形状部分地合理化。通常,随着N-取代基尺寸的增加,增强作用也随之增加。对于小号Ñ在2个反应中,速率按苄基>甲基≃s-烷基>连续链伯烷基≃新戊基的顺序降低。与涉及其他离去基团的文献数据进行比较后,通过参考每个系列中的乙基化合物进行标准化,这再次表明,大于乙基的基团在系列(1),(2),尤其是(3)中的反应往往比预期的要快,并且甲基倾向于反应