Ring-Selective Functionalization of N,N‘-Diarylureas by Regioselective N-Alkylation and Directed Ortho Metalation

[reaction: see text]. Unsymmetrical N,N'-diarylureas may be alkylated regioselectively at the more sterically congested nitrogen atom. The resulting mono-N-alkylated ureas undergo directed metalation (ortholithiation) with sec-BuLi to yield, on electrophilic quench, products functionalized regioselectively at the ring bearing the alkylated nitrogen atom.