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

Abstract

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, one 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.