Selective Ortho and Benzylic Functionalization of Secondary and Tertiary p-Tolylsulfonamides. Ipso-Bromo Desilylation and Suzuki Cross-Coupling Reactions

Kinetic vs thermodynamic deprotonation studies on secondary and tertiary sulfonamides 1 and 2 using n-BuLi have been carried out. While both 1 and 2 show kinetic ortho-metalation, thermodynamic conditions lead to ortho and benzylic deprotonation, respectively (Figures and ). Metalation of 1 using the n-BuLi/KOtBu superbase led to regioselective benzylic metalation (Figure ); LDA deprotonation was also briefly explored. Application of the developed conditions allows the synthesis of diverse sulfonamide products 5a−e, 6a−e, 7a,b, and 8a−e. Ipso-bromo desilylation reactions afford sulfonamides 9a,b while Suzuki cross-coupling reactions furnish biaryl sulfonamides 11a−c.