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. Author manuscript; available in PMC: 2009 Nov 13.
Published in final edited form as: Tetrahedron Lett. 2009 May 13;50(19):2252–2255. doi: 10.1016/j.tetlet.2009.02.210

Table 4.

Enantioselective four-component reaction for the synthesis of pyranopyrazoles with catalyst 2a

graphic file with name nihms125436f7.jpg
Entry 12 Additive (equiv) Solvent Time (h) Yieldb (%) eec (%)
1 12a — CH2Cl2 23 28 16
2 12a MgSO4 (1) CH2Cl2 27 21 89
3 12a Na2SO4 (1) CH2Cl2 27 25 96
4 12a MS(4 Å)d CH2Cl2 27 20 90
5 12a Na2SO4 (2)e CH2Cl2 28 43 >99
6 12a Na2SO4 (2) CHCl3 24 28 >99
7 12a Na2SO4 (2) MeCN 24 24 >99
8 12a Na2SO4 (2) THF 24 30 98
9 12a Na2SO4 (2) Benzene 24 <5 nd
10 12c Na2SO4 (2) CH2Cl2 17 75 23
11 12d — CH2Cl2 21 73 58
12 12g Na2SO4 (2) CH2Cl2 17 80 2
13 12i Na2SO4 (2) CH2Cl2 18 82 34
a

Unless otherwise indicated, all reactions were carried out with 13 (0.10 mmol), 14 (0.10 mmol), 15 (0.10 mmol), 16 (0.10 mmol), and the catalyst (5 mol %) in the indicated solvent (2.0 mL) at rt.

b

Yield of isolated product after chromatography.

c

Determined by HPLC analysis on a ChiralPak AS column.

d

Molecular sieves (40 mg) were added.

e

Carried out at 0 °C.