Reactions of trimethylstannide and trimethylsiliconide anions with aromatic and heteroaromatic substrates

Abstract

AbstractA 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. Copyright © 2002 John Wiley & Sons, Ltd.