Convenient synthesis of 1H-Indol-1-yl boronates via palladium(0)-catalyzed borylation of bromo-1H-indoles with 'pinacolborane'

An atom-economic Pd-0-catalyzed synthesis of a series of pinacol-type indolylboronates 3 from the corresponding bromoindole substrates 2 and pinacolborane (pinBH) as borylating agent was elaborated. The optimal catalyst system consisted of a 1: 2 mixture of [Pd(OAC)(2)] and the ortho-substituted biphenyl-phosphine ligand L-3 (Scheme 4, Table). Our synthetic protocol was applied to the fast, preparative-scale synthesis of 1-substituted indolylboronates 3a-h in the presence of different functional groups, and at a catalyst load of only 1 mol-% of Pd.