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. Author manuscript; available in PMC: 2013 Jun 19.
Published in final edited form as: J Am Chem Soc. 2008 Jan 4;130(4):1440–1452. doi: 10.1021/ja0773507

Table 8.

Comparison of Lewis and Brønsted Acid Catalysts for Cycloisomerization of Allenyl Ketones

graphic file with name nihms382578u8.jpg

entry R Ar cat (mol %) additive (mol %) solvent T, °C time, h NMR yield (%)a,b
1 Ph p-C6H4-CN TfOH (10) – toluene 100 1.5 96
2 Ph p-C6H4-CN TfOH (10) TTBP (40) toluene 100 2.0 > 99
3 Ph p-C6H4-CN Sn(OTf)2 (5) TTBP (20) toluene 100 2.0 91
4 Ph p-C6H4-CN TfOH (20) – DCE rt 1.0 96
5 Ph p-C6H4-CN TfOH (20) TTBPc (40) DCE rt 24 0
6 Ph p-C6H4-CN TfOH (20) TTBP (40) DCE 95 48 36
7 Ph p-C6H4-CN TMSOTf (20) – DCE rt 1.0 > 99
8 Ph p-C6H4-CN TMSOTf (20) TTBP (40) DCE rt 4.0 0
9 Ph p-C6H4-CN TMSOTf (20) TTBP (40) DCE 95 24 61
10 Ph p-C6H4-CN AgOTf (20) – DCE 80 2.0 > 99
11 Ph p-C6H4-CN AgOTf (20) TTBP (40) DCE 80 2.0 0
12 Ph p-C6H4-CN AgOTf (20) TTBP (40) DCE 95 48 19
13 Ph p-C6H4-CN Sn(OTf)2 (5) – toluene 100 1.5 > 99
14 Ph p-C6H4-OMe TfOH (10) – toluene 100 1.0 88
15 Ph p-C6H4-OMe In(OTf)3 (5) – toluene 100 2.0 79
16 Me Ph TfOH (10) – toluene 100 1.0 52
17 Ph Ph In(OTf)3 (5) – toluene 100 12 77
a

Reactions were performed on 0.1 mmol scale.

b

Dibromomethane was used as the standard.

c

TTBP = 2,4,6-tris-tert-butylpyrimidine.