Patent ID: 7393980

Claim:
A process for carrying out a nucleophilic substitution on an aromatic substrate, comprising the step of: contacting said substrate of general formula (III): Ar—Ξ (III) wherein Ar is an aromatic group where the nucleus carrying the group Ξ is electron-poor, either because it contains at least one heteroatom in its ring or because the sum of the Hammett constants, σ p s, of its substituents, apart from said Ξ, is at least 0.2, and, wherein Ξ is a leaving group selected from the aroup consisting of halogens, pseudo halogens and a nitro group, optionally in the form of an anion Ξ; with a composition used as a reaction medium for reacting said substrate, said composition comprising: a) at least one ionic quatemary phosphonium compound whose cation is of general formula I′: wherein R 1 , R 2 , R 3 and R 4 , which are identical or different, are hydrocarbon radicals, and whose anion or anion mixture ensures electroneutrality; b) a co-anion; c) a nucleophilic substituent, optionally in salt form; and d) a polar solvent, where the polar solvent is present in an amount such that the ratio by mass between the sum of the polar solvents and the sum of the phosphonium salts ([S.P.]/[P+1]), i.e. [S.P.]/(a+b), is not more than 1, and the sum of (a)+(b)+(c)+(d) represents 100% of said liquid phase; and where the molar ratio between the phosphonium compound and the substrate at the start of said reaction is at least 2/3.