A new class of easily activated palladium precatalysts for facile C-N cross-coupling reactions and the low temperature oxidative addition of aryl chlorides

Abstract

A new class of one-component Pd precatalysts bearing biarylphosphine ligands is described. These precatalysts are air- and thermally stable, are easily activated under normal reaction conditions at or below room temperature, and ensure the formation of the highly active monoligated Pd(0) complex necessary for oxidative addition. The use of these precatalysts as a convenient source of LPd(0) in C-N cross-coupling reactions is explored. The reactivity that is demonstrated in this study is unprecedented in palladium chemistry.

Figure 1

Synthesis of precatalysts 4-6.

Figure 2

Calorimetric scans of the addition of precatalysts 4-6 to NaOt-Am in dioxane at room temperature; X-ray crystal structure of 5.

Figure 3

Effect of Pd source on the cross-coupling of aniline and 4-chloroanisole using 0.1% Pd and ligand 1 at 80 °C.

Figure 4

³¹P{¹H} NMR spectra of: (a) 7 in toluene/PhCl at −40 °C and (b) 7 in toluene/PhCl w/ LHMDS (1 equiv.) after 110 min at −40 °C.