Synthetic use of 1,1,2,2-tetraphenyldisilane for the preparation of biaryls through the intramolecular free radical ipso-substitution of N-(2-bromoaryl)arenesulfonamides

Treatment of various N-methyl-N-(2-bromoaryl)arenesulfonamides (1a–g, 1i, and 1m) with 1,1,2,2-tetraphenyldisilane and AIBN under heating conditions gave the corresponding biaryl products (2a–g, 2i, and 2m) in moderate yields through the intramolecular radical ipso-substitution. However, N–H free N-(2-bromoaryl)arenesulfonamides 1h and 2-bromoaryl arenesulfonate 1j did not give the corresponding biarys. 1,1,2,2-Tetraphenyldisilane is the most effective reagent for 1,5-ipso-substitution on the sulfonamides among typical radical reagents such as diphenylsilane, tributyltin hydride, tris(trimethylsilyl)silane, and 1,1,2,2-tetraphenyldisilane. Furthermore, 1,1,2,2-tetraphenyldisilane has the advantages of low toxicity, stability, and ease of preparation.