Skip to main content
. Author manuscript; available in PMC: 2006 Jun 8.
Published in final edited form as: J Am Chem Soc. 2005 Jul 20;127(28):10039–10044. doi: 10.1021/ja0527976

Table 1.

Additive Screeninga,b

graphic file with name nihms-5984-0002.jpg
none HOBt HOAt PFP HYP DMAP
Ti(Oi-Pr)4 30 24 17 11 30 34
Zr(Ot-Bu)4 33 79 90 81 85 24
Hf(Ot-Bu)4 38 80 84 77 75 35
a

Reaction conditions: ethyl hippurate (0.50 mmol), benzylamine (0.50 mmol), catalyst (0.05 mmol), additive (0.10 mmol), toluene (1 mL), 60 °C, 1 h. Percent conversion based on 1H NMR analysis of the crude reaction mixture.

b

HOBt = 1-hydroxybenzotriazole, HOAt = 1-hydroxy-7-azaben-zotriazole, PFP = pentafluorophenol, HYP = 2-hydroxypyridine, DMAP = 4-(dimethylamino)pyridine.