Table 3.
Solvent-free regioselective silylations committing secondary alcoholsa.
| Entry | Substrate | Time (h) | Product, isolated yield |
| 1 | 1 | 4 |
 17, 72% |
| 2 | 3 | 4.5 |
 18, 60% |
| 3 | 8 | 5 |
 19, 56% |
| 4 |
 20 |
1 |
 21, 56% |
| 5 |
 22 (α:β ca. 2.5) |
6 |
 23 (α:β ca. 4), 75% |
| 6 |
 24 (α:β ca. 2.5) |
6 |
 25 (α:β ca. 4), 50% (95%)b |
aGeneral conditions (entries 1–3): pyridine (5 equiv), TBDMSCl (2.5 equiv), TBAB (0.3 equiv), 50 °C. For entry 4: pyridine (6 equiv), TBDMSCl (3.5 equiv), TBAB (0.3 equiv), rt. For entries 5 and 6: pyridine (3 equiv), TBDMSCl (1.5 equiv), TBAB (0.15 equiv), 50 °C. bIn parenthesis is indicated the conversion yield.