Diphenyliodonium-2-carboxylate monohydrate

With benzenediazonium-2-carboxylate or diphenyliodonium-2-carboxylate monohydrate, benzyne precursors, 11 yield 1818 (Scheme 34). 

Diphenyliodonium-2-carboxylate monohydrate. Mol, wt, 341,13, m.p, 220°, dec. This stable and safe reagent is useful for the generation of benzyne in an aprotic solvent in the presence of a reactive diene as trapping agent. The original preparative procedure has been improved to a point such that 2 g. of o-iodobenzoic acid (Aldrich, Eastman) can be converted into 2.1 g. of the benzyne precursor in li-2 hrs. working time. The synthesis of 1,2,3,4-tetraphenylnaphthalene can be... 

This synthesis of 1,2,3,4-tetraphenylnaphthalene (7) demonstrates the transient existence of benzyne (5), a hydrocarbon that has not been isolated as such. The precursor, diphenyliodonium-2-carboxylate (4), is heated in an inert solvent to a temperature at which it decomposes to benzyne, iodobenzene, and carbon dioxide in the presence of tetraphenylcyclo-pentadienone (6) as trapping agent. The preparation of the precursor (4) illustrates oxidation of a derivative of iodobenzene to an iodonium salt (2) and the Friedel-Crafts-like reaction of the substance with benzene to form the diphenyliodonium salt (3). Neutralization with ammoniuim hydroxide then liberates the precursor, inner salt (4), which, when obtained by crystallization from water, is the monohydrate. 

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