Chapter 2 Electrophilic Chemistry in Ionic Liquids

摘要

Room temperature ionic liquids (Ils), with low nucleophilicity counterions (Otf~-, FSO_3~-, PF_6~-, BF_4~- etc) constitute unique environments for exploring ionic reactions involving electron-deficient intermediates, in particular carbocations and onium ions. Lewis acids that typically show limited or no solubility in regular organic solvents can in many cases be dissolved/immobilized in imidazolium-based Ils. Moreover, these "designer solvents" appear to be ideal media for utilizing onium salts (I.e. diazonium, selectfluor? etc) as reagents for synthesis because of their increased solubility in Ils as compared to regular organic solvents (onium salt reagents dissolved in onium salt solvents!). Current interest and activity of this laboratory in the ionic liquids area center around their potential application as solvents and as catalysts in fundamentally important electrophilic transformations, specially those that are carried out on large scale in industry such as nitration, alkylation, acylation and fluorination. The present review summarizes our survey studies in aromatic nitration, aromatic fluorination using NF reagents, fluorodediazoniation (Balz-Schiemann reaction), trans-acylation and deacylation of aromatic ketones, and in adamantylation of aromatics.