1984-65-2Relevant articles and documents
Masked N-Heterocyclic Carbene-Catalyzed Alkylation of Phenols with Organic Carbonates
Lui, Matthew Y.,Yuen, Alexander K. L.,Masters, Anthony F.,Maschmeyer, Thomas
, p. 2312 - 2316 (2016/10/24)
An easily prepared masked N-heterocyclic carbene, 1,3-dimethylimidazolium-2-carboxylate (DMI-CO2), was investigated as a “green” and inexpensive organocatalyst for the alkylation of phenols. The process made use of various low-toxicity and renewable alkylating agents, such as dimethyl- and diethyl carbonate, in a focused microwave reactor. DMI-CO2 was found to be a very active catalyst and excellent yields of a range of aryl alkyl ethers were obtained under relatively benign conditions. The observed difference in the conversion behavior of phenol methylation, in the presence of either the carbene or 1,8-diazabicycloundec-7-ene (DBU) catalyst, was rationalized on the basis of mechanistic investigations. The primary mode of action for the N-heterocyclic carbene is nucleophilic catalysis. Activation of the dialkyl carbonate electrophile results in concomitant evolution of an organo-soluble alkoxide, which deprotonates the phenolic starting material. In contrast, DBU is initially protonated by the phenol and thus consumed. Subsequent regeneration and participation in nucleophilic catalysis only becomes significant after some phenolate alkylation occurs.
A safe and economical synthesis of 3-(trifluoromethoxy) aniline from 2-chlorophenol
Langlois, Bernard,Soula, Gerard
, p. 925 - 929 (2007/10/02)
A simple, safe and realistic synthesis of 3-(trifluoromethoxy) aniline from 2-chlorophenol is proposed, the key step being a regiospecific arynic amination of 2-chloro (trifluoromethoxy) benzene.This method has been extended to the synthesis of 4-chloro-3-(trifluoromethoxy) aniline from 2,6-dichlorophenol.Some unusual products are obtained during the reaction between sodium amide and 2-chloro (chlorodifluoromethoxy) benzene, the formation of which is discussed.
THE REACTIONS OF UNACTIVATED ARYL HALIDES WITH SODIUM METHOXIDE IN HMPA; SYNTHESIS OF PHENOLS, ANISOLES, AND METHOXYPHENOLS
Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
, p. 193 - 198 (2007/10/02)
Sodium methoxide reacts with dichlorobenzenes in HMPA to give the chloroanisoles as a result of a SNAr process.Excess MeONa then effects the demethylation of the ethers to give the chlorophenols via an SN2 reaction.With tri- and tetrachlorobenzenes the initially formed chloroanisoles can be dealkylated to chlorophenols or can suffer further substitution to give the chlorodimethoxybenzenes; these react with excess MeONa to give the chloromethoxyphenols.The results obtained with the various isomers of the di-, tri-, and tetrachlorobenzenes are presented and discussed on the basis of the electronic effects of the substituents.
