GB831356A - Preparation of 3:3', 5:5'-tetraalkyldiphenoquinones - Google Patents

Abstract

3:31:5:51 - Tetra - alkyldiphenoquinones are prepared by treating, in a substantially homogeneous liquid system, a 4-halo-2:6-dialkyl phenol with at least an equimolar amount of a basic compound having a dissociation constant of at least 1.6 x 10-3 at 25 DEG C. The halogen atom on the ring is one having an atomic weight of at least 30 and preferably at least one of the substituent alkyl groups has a branched chain at the a carbon atom. In a preferred process the 4-halo-2 : 6 dialkyl phenol is formed in situ by treating a 2 : 6-dialkyl phenol with elementary halogen. The preferred phenols are those where all the alkyl groups are secondary or tertiary and each containing up to about 12 carbon atoms. The basic compound may be any strong organic or inorganic base, for example guanidine, piperidine, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, alkali metal alcoholates or alkali metal hydroxides. When an aqueous inorganic base, e.g. aqueous sodium hydroxide, is used an inert organic solvent may be added to maintain the homogeneity of the reaction mixture. Examples of suitable solvents are alcohols, particularly lower monohydric alcohols, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, dibutyl ketone, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether or diethylene glycol diethyl ether. The glycol ethers are particularly suitable as they readily dissolve the reactants but do not readily dissolve the substituted diphenoquinones. When an organic base of strength similar to that of piperidine is used the oxidation-coupling reaction may be accelerated by heating the reactants and high boiling solvents such as liquid hydrocarbons with b.p. above 150 DEG C., nitrobenzene, o-dichlorbenzene, diethylene glycol diethyl ether or dibutyl ether, stearyl alcohol or cetyl alcohol may be used. When strong organic bases are used addition of further solvent is often unnecessary. When strong bases e.g. sodium hydroxide, are used the reaction temperature may be in the range 0-110 DEG C.; when weaker bases, e.g. of piperidine, are used higher temperatures, e.g. 60-200 DEG C., are required. In the examples 3 :31 : 5 : 51 - tetra - tert. butyl diphenoquinone is prepared by (1) refluxing 4-bromo-2 : 6-ditert. butyl phenol with aqueous sodium hydroxide in dioxane; (2) refluxing 4-chloro-2 : 6-di-tert. butyl phenol with piperidine in nitrobenzene; (3) refluxing 4-chloro-2 : 6-di-tert. butyl phenol with sodium methoxide in methanol. Specifications 686,261 and 687,293 are referred to.