Reactions of Trimethylstannide and Trimethylsiliconide Anions with Aromatic and Heteroaromatic Substrates

JOSE ALBERTO POSTIGO; E VAILLARD, SANTIAGO; A ROSSI, ROBERTO

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

John Wiley and Sons

Lugar: Chichester; Año: 2002 vol. 15 p. 889 - 893

0894-3230

A parallel study was carried out on the reactions of Me3Sn and Me3Si ions towards aromatic and heteroaromatic substrates in hexamethylphosphoramide (HMPA) as solvent. It was found that Me3Si ions are more reactive and therefore less selective than Me3Sn ions. In HMPA, PhI and PhBr react with Me3Sn ions through an HME pathway. PhCl also reacts by an HME reaction, but under photostimulation the SRN1 mechanism competes with the HME process. With PhF as substrate, Me3Sn ions afford (4-fluorophenyl)trimethylstannane, presumably through a hypervalent tin species. Under irradiation, the SRN1 mechanism operates concurrently with the formation of the hypervalent tin species. Me3Si ions, on the other hand, react with PhX (X = Cl, Br, I) to yield the ipso substitution product, presumably through the intermediacy of a hypervalent silicon species. PhF affords, upon reaction with Me3Si ions, o- and p-fluorotrimethylsilylbenzenes together with the ipso substitution product PhSiMe3. A novel type of nucleophilic substitution mechanism takes place with Me3Si ions upon reaction with aromatic and heteroaromatic substrates without classical leaving groups in HMPA