A New Method for High-Yield Cyclopalladation of Primary and Secondary Amines. Atom-Efficient Open-to-Air Inexpensive Synthesis of Buchwald-Type Precatalysts

A new method for high-yield cyclopalladation of primary and secondary amines involving the corresponding ammonium triflates, instead of the amines generally employed, is reported. The method is applied for the synthesis of Buchwald-type precatalysts [Pd(C,N-C6H4CH2CH(R′)NHR-2)X(phosphine)] that can be easily prepared by reaction of Pd(OAc)2, 1 equiv of the ammonium triflate [PhCH2CH(R′)NH2R]OTf, and an excess of NaX and then treating the resulting complexes [Pd2(C,N-C6H4CH2CH(R′)NHR-2)2(μ-X)2] with the appropriate phosphine. This new method has several advantages over Buchwald's reported synthesis.