Coupling reagent in the presence of benzyl and tosyl protected groups: Chem. Lett., 577 (1975); Tetrahedron Lett., 31, 2839 (1978); Synthesis, 413 (1983). Also used in the Pd-catalyzed coupling of ɑ-amino esters: Transition Metal Chem. (London), 8, 262 (1983).