, Chem. Rev, vol.111, p.6557, 2011.
, Montalbetti and V. Falque, pp.97-1755, 1197.
See also (b) For other recent catalysed amide bond formation see, Pe´rez-Maciasb and Jesus Alca´zar, pp.7453-61, 1960. ,
, J. Org. Chem. Angew. Chem. Int. Ed, vol.77, pp.8386-8433, 2008.
, Eur. J. Org. Chem, p.1100, 2015.
, J. Org. Chem, pp.80-4532, 2015.
9 The cooperative catalytic effect is still unclear but allowed to obtain Boc-Phe-Val-OMe in 55% yield in the presence of 50 mol% of 1 and 50 mol% of 2 while 100 mol% of 2 delivered <2% yield, Eur. J. Org. Chem. J. Org. Chem. J. Am. Chem. Soc. Tetrahedron Letters, vol.5692, issue.133, pp.5664-3724, 1997. ,
11 The synthesis of 9k is remarkably low yielding. See supporting information for details, Chem. Sci. J. Am. Chem. Soc. Tetrahedron J. Org. Chem. Org. Biomol. Chem, vol.134, issue.12, pp.945-8260, 1305. ,