Scope of the pyrone transformation with diamines 2a.
| Bis-adduct | Ar | R | Yield from enaminone 3, % (Method A) | Yield from diamine, % (Method B) | 5E,5′E-4 : 5E,5′Z-4 | 
|---|---|---|---|---|---|
| 4a | Ph | H | 64 | 57 | 50 : 17 | 
| 4b | 4-MeOC6H4 | H | 73 | 38 | 69 : 17 | 
| 4c | 4-ClC6H4 | H | 65 | 75 | 39 : 26 | 
| 4d | 2-Th | H | 75 | 31 | 71 : 14 | 
| 4e | 2-Th | Me | 79 | 63 | 74 : 10 | 
Method A: pyrone 1 (0.26 mmol) and enaminone 3 (0.26 mmol) were stirred in EtOH (2 mL) at 20 °C for 24 h. Method B: pyrone 1 (0.72 mmol) and diamine 2 (0.36 mmol) were stirred in EtOH (2 mL) at 0 °C for 1 h and then at 20 °C for 24 h.