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, a nd 1m) with 1,1,2,2-tetraphenyldisilane and AIBN under heating conditions g ave the corresponding biaryl products (2a-g, 2i, and 2m) in moderate yields through the intramolecular radical ipso-substitution. However, N-H foe N-( 2-brornoaryl)arenesulfonamides Ih and 2-bromoaryl arenesulfonate 1j did not give the corresponding biarys. 1,1,2,2-Tetraphenyldisilane is the most eff ective reagent for 1,5-ipso-substitution on the sulfonamides among typical radical reagents such as diphenylsilane, tributyltin hydride, tris(trimethy lsilyl)silane, and 1,1,2,2-tetraphenyldisilane. Furthermore, 1,1,2,2 tetrap henyldisilane has the advantages of low toxicity, stability, and ease of pr eparation. (C) 2001 Elsevier Science Ltd. All rights reserved.