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. 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 2.

Evaluation of Catalyst Composition and Reaction Solventa

entry Zr(Ot-Bu)4: HOAt solvent  conditions conversionb (%)
1 2:1 toluene 60 °C, 1 h 85
2 1:1 toluene 60 °C, 1 h 96
3 1:2 toluene 60 °C, 1 h 90
4 1:3 toluene 60 °C, 1 h 85
5 1:4 toluene 60 °C, 1 h 78
6 1:1 toluene rt, 12 h 97c (92d)
7 1:1 benzene rt, 12 h 97c
8 1:1 DCE rt, 12 h 85c
9 1:1 THF rt, 12 h 95c
10 1:1 1,4-dioxane rt, 12 h 80c
11 1:1 CH3CN rt, 12 h 85c
a

Reaction conditions: ethyl hippurate (0.50 mmol), benzylamine (0.50 mmol), Zr(Ot-Bu)4 (0.05 mmol), HOAt and solvent (1 mL).

b

Conversion based on 1H NMR analysis of the crude reaction mixture.

c

1.1 equiv of benzylamine employed.

d

Isolated yield after purification by silica gel chromatography.