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. Author manuscript; available in PMC: 2012 Jun 3.
Published in final edited form as: J Org Chem. 2011 May 4;76(11):4721–4727. doi: 10.1021/jo200425m

Table 1.

Optimization of conditions for the cyclization of 5b to 1a

graphic file with name nihms294138u2.jpg
entry ligand base solvent temp (time) results (yield)b
1 X-Phos Cs2CO3 toluene 100°C (24 h) no reaction
2 X-Phos NaOt-Bu toluene 100°C (24 h) no reaction
3 X-Phos NaOt-Bu DMF 120°C (24 h) dechlorination
4 X-Phos NaOt-Bu DMA 120°C (24 h) dechlorination
5 (t-Bu)3P ·HBF4 NaOt-Bu DMA 120°C (24 h) 32 % yield (mixture of 1 and 6) + decomposed material
6 (t-Bu)3P ·HBF4 K2CO3 DMA 120°C (24 h) 52 % 1 + 30 % 6
7 (t-Bu)3P ·HBF4 K2CO3 DMA 120°C (16 h) 56 % 1 + 32 % 6
8 Cy3P ·HBF4 K2CO3 DMA 120°C (16 h) 55 % 1 + 30 % 6
a

The reactions were carried out using 5b (0.1 mmol), Pd(OAc)2 (0.01 mmol), ligand (0.02 mmol), and base (0.2 mmol) in solvent (1.0 mL) under argon.

b

Isolated yield.