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. Author manuscript; available in PMC: 2008 Nov 11.
Published in final edited form as: J Am Chem Soc. 2007 Apr 4;129(17):5334–5335. doi: 10.1021/ja0709167

Table 1.

Optimization of Conditionsa

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entry catalyst conditions yield (%)b d.r.c
1 A CH2CI2, 23 °C, 24 h 35 >20:1
2 B CH2CI2, 23 °C, 24 h 29 >20:1
3 C CH2CI2, 23 °C, 24 h 39 >20:1
4 C THF, 50 °C, 24 h 15 >20:1
5 C 10:1 THF/tBuOH, 50 °C, 24h 23 >20:1
6 C CH2CI2, 23 °C, 3 h 45 >20:1
7 C 10:1 THF/tBuOH, 50 °C, 3h 59 >20:1
8 C CH2CI2, 40 °C, 2 h 79 >20:1
9d C CH2CI2, 40 °C, 2 h 46 >20:1

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a

2 equiv. 1a and 1 equiv. 2a.

b

Isolated yield after purification.

c

As determined by 1H NMR spectroscopy.

d

10 mol % C, 10 mol % DBU.