Table 1. Study of the Cyclization Reaction of 3a for the Achievement of Piperazinone 4a.
entry | reagents | time (h) | yield (4a) (%) | yield (5a) (%) | ||
---|---|---|---|---|---|---|
1 | TFA 50% | TES 10% | CH2Cl2 40% | 4 | 50 | 19 |
2 | TFA 50% | TIPS 10% | CH2Cl2 40% | 4 | 66 | 17 |
3 | TFA 50% | TIPS 40% | CH2Cl2 10% | 4 | 70 | 0 |
4 | TFA 50% | TIPS 40% | CH2Cl2 10% | 16 | 75 | 0 |
5 | TFA 50% | TIPS 40% | 1,2-DCE 10% | 16 | 85 | 0 |