Table 3. Substrate Scope of the Tandem Pinacol Coupling/Pinacol Rearrangement of Diones 3a–oa.
| Entry | R | Yield (%)b |
|---|---|---|
| 1c | Ph (3a) | 63 |
| 2 | 4-Cl-C6H4 (3b) | 40 |
| 3 | 4-F-C6H4 (3c) | 65 |
| 4 | 3-F-C6H4 (3d) | 57 |
| 5 | 2-F-C6H4 (3e) | 40 |
| 6 | 4-CF3-C6H4 (3f) | 12 |
| 7 | 4-CN-C6H4 (3g) | 16 |
| 8 | 4-Me-C6H4 (3h) | 80 |
| 9 | 4-MeO-C6H4 (3i) | 82 |
| 10 | 3-MeO-C6H4 (3j) | 62 |
| 11 | 2-MeO-C6H4 (3k) | 56 |
| 12 | 2-Thiophenyl (3l) | >5d |
| 13 | 3-Pyridyl (3m) | N.D. |
| 14 | Bn (3n) | 42 |
| 15 | c-Pentyl (3o) | 45 |
a
Reaction conditions: step 1: dione 3a–o (0.50 mmol) in THF (5.0 mL) was added to a solution of SmI2 (0.01 M in THF, 2.0 mmol) heated at 50 °C and stirred for 0.5 h; step 2: p-TsOH·H2O (0.050 mmol, 10 mol %) in MeCN (1.0 mL).
b
Yields of isolated products 5a–o were based on 3a–o over two steps.
c
Step 1 was conducted at room temperature.
d
Yield of 5l was determined by 1H NMR analysis using triphenylmethane as an internal standard.