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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: Org Lett. 2011 Mar 4;13(7):1868–1871. doi: 10.1021/ol2003836

Table 2.

Optimization of the double allylboration leading to 6a

graphic file with name nihms278779u3.jpg
entry PhCHO (equiv) BF3·OEt2 (equiv) % yield 6ab ratio E/Zc ratio 13/6a/14c
1 0.75 1.5 60 > 20:1 0:89:11
2 0.85 1.5 73 > 20:1 0:100d:0
3 0.95 1.5 51 > 20:1 8:92:0
4e 0.85 1.5 30 6:1 0:100:0
5f 0.85 - 77 6:1 0:100:0
a

Reaction conditions: solvent: toluene/CH2Cl2; hydroboration: −30 °C, 1 h; first allylboration: −78 °C, 4 h; second allylboration: −78 °C, 4 h; workup: pH 7 buffer (KH2PO4/NaOH).

b

Isolated yields.

c

Determined by 1H NMR analysis.

d

6a obtained with > 20:1 dr and 97% ee, determined by Mosher ester analysis.

e

Second allylboration: 0 °C, 2h.

f

Second allylboration: −78 to 20 °C, 12 h.