Acid-Catalyzed Dehydration of Naphthalene-<i>cis-</i>1,2-dihydrodiols: Origin of Impaired Resonance Effect of 3-Substituents
作者:Jaya Satyanarayana Kudavalli、Derek R. Boyd、Narain D. Sharma、Rory A. More O’Ferrall
DOI:10.1021/jo201591r
日期:2011.11.18
substituted naphthalene-cis-1,2-dihydrodiols occur with loss of the 1- or 2-OH group to form 2- and 1-naphthols, respectively. Effects of substituents MeO, Me, H, F, Br, I, and CN at 3-, 6-, and 7-positions of the naphthalene ring are consistent with rate-determining formation of β-hydroxynaphthalenium ion (carbocation) intermediates. For reaction of the 1-hydroxyl group the 3-substituents are correlated by
取代的萘-顺式-1,2-二氢二醇的酸催化脱水发生,但失去了1-或2-OH基团,分别形成了2-和1-萘酚。萘环的3、6和7位上的取代基MeO,Me,H,F,Br,I和CN的作用与速率确定的β-羟基萘离子(碳化)中间体的形成一致。对于1-羟基基团的反应,通过Yukawa–Tsuno关系将ρ= −4.7和r = 0.25或通过σp常数将ρ= −4.25关联3个取代基。对于2位羟基的反应的3-取代基是由σ相关米ρ= −8.1的常数。1-羟基的相关性暗示+ M取代基(MeO,Me)与碳正离子反应中心的共振相互作用出乎意料的弱,但与3-取代的苯-顺式-1,2的酸催化脱水的相应相关性一致-二氢二醇,其ρ= -6.9和r = 0.43。相反,在萘环的6位和7位上的取代基与σ +相关对于1-羟基的反应,ρ= -3.2,对于2-羟基的反应,ρ= -2.7。这些取代基效应所隐含的未削弱的共振似乎与先前关于3-取