Iodomethyltriphenylphosphonium iodide

Wittig reactions are commonly used for the elaboration of side-chains. When l-methylimidazole-5-carbaldehyde is heated with iodomethyltriphenylphosphonium iodide, and the iodoethenyl product is treated with /z-butyllithium in THF, the ultimate product is the highly toxic 5-ethynyl-l-methylimidazole 616 (Scheme 131). 

A suspension of iodomethyltriphenylphosphonium iodide in THF treated slowly with 1 M Na-bis(trimethylsilyl)amide in the same solvent at room temp., stirred for 1 min, cooled to —60°, treated with a little HMPA, cyclohexanecarboxaldehyde added after cooling to — 78°, the cooling bath removed, and stirred for 30 min (2-iodoethenyl)-cyclohexane. Y 71% (Z/E 15.5/1). cf. Synth. Meth. 30, 620. F.e.s. G. Stork, K. Zhao, Tetrahedron Letters 30, 2173 (1989). 

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