We started our investigation using azadipeptide 2a derived from proline with the C-terminal protected with a tert-butyl group as a model subtrate. Reaction of the later with TIPS-EBX (3a) for 1 hour in the presence of Cu(CH3CN)4BF4 and potassium tert-butoxide led to the formation of 4a in an encouraging 20% yield (Table , entry 1). A similar result could be obtained using Cs2CO3 as a milder base (entry 2). Increased formation of the desired product was observed when the reaction was heated to 40 °C (entry 3). Replacing acetonitrile by i-PrOH or DCE increased the yield to 48% and 60% respectively (entries 4 and 5). Several copper catalysts can promote the reaction, with the best result obtained using CuI, affording 76% of 4a (entries 6-8). No difference could be observed when the transformation was carried out with an excess of TIPS-EBX (3a) (entry 9). Control reactions without base or copper catalyst resulted in, respectively, no reaction or degradation of the azapeptide (entries 10 and 11). Finally, DCM could be used as an alternative to DCE without impacting the reaction outcome (entry 12). a Reaction conditions: azapeptide 2a (1.0 equiv.), TIPS-EBX (3a) (1.0 equiv.), catalyst (5 mol%), base (1.5 equiv.), solvent (0.1 M), reactions were carried out under air on a 0.05 mmol scale. Isolated yields are reported. b TIPS-EBX (3a) (1.5 equiv.)