One-pot synthesis of phosphorylnaphth[2,1-d]oxazoles and products as P,N-ligands in C–N and C–C formation

Abstract

Phosphanylnaphtho[2,1-d]oxazoles were synthesized successfully through one-pot phosphonation of naphthoquinone with diaryl(alkyl)phosphine oxides and Cu-catalyzed oxidative condensation with imines, followed by methylation and reduction. Upon applying 4-phosphanylnaphtho[2,1-d]oxazole as a P,N-chelating ligand, Pd-catalyzed C–N formation of amines or nitrobenzene as well as Ni-catalyzed C–C formation and the synthesis of quinoline proceeded successfully. The reaction was facilely scaled up to give N-benzylaniline 15a in a gram scale synthesis. This research provided a facile and convenient protocol to synthesize phosphanylnaphtho[2,1-d]oxazoles, which could be applied as an efficient P,N-ligand in transition-metal-catalyzed C–N and C–C formation to produce the desired products in high yields with wide functional group tolerance under small catalyst loading, solvent-free conditions in many reactions.