Table 2.
Asymmetric Betti reaction of 1-naphthol (12) with N-tosylimine 13 catalyzed by thioureas 1–7 or thiosquaramides 8–11.
| Entry | Catalyst | Yield [%] 1 | ee [%] 2 (Conf.) 3 |
|---|---|---|---|
| 1 | 1 | 98 | 80 (S) |
| 2 | 2 | 86 | 50 (S) |
| 3 | 3 | 98 | 68 (S) |
| 4 | 4 | 93 | 62 (S) |
| 5 | 5 | 95 | 64 (S) |
| 6 | 6 | 80 | 58 (R) |
| 7 | 7 | 98 | 60 (R) |
| 8 | 8 | 75 | 56 (S) |
| 9 | 8·HCl | 53 | 40 (S) |
| 10 | 9 | 80 | 42 (S) |
| 11 | 9·HCl | 30 | 30 (S) |
| 12 | 10 | 70 | 20 (R) |
| 13 | 10·HCl | 45 | 16 (R) |
| 14 | 11 | 72 | 36 (R) |
| 15 | 11·HCl | 50 | 28 (R) |
Reagents and conditions: 1-naphthol (0.015 mmol, 3 eq.), N-tosylimine (0.05 mmol, 1 eq.), 10 mol% cat., toluene (1 mL), molecular sieves 4 Å, 0 °C, 20 h. 1 Isolated product. 2 Determined by HPLC analysis, Chiralpak AD-H, hexane:iPrOH 90:10, 1 mL/min, 235 nm. 3 The configuration was established by comparison with the optical rotation from the literature [14,35].