Table 1.
Vinyl | Yield[c] | Conv. | Stability[d] | |
---|---|---|---|---|
ethers[a] | Alcohol | Pyridazine | [%] | [%] |
1 a [b] | 61 | 49 | 100 | 100[e] |
1 b | 68 | 65 | 73 | 100 |
1 c | 57 | 72 | 100 | 77 |
1 d | 50 | 47 | 56 | 100 |
1 e | 65 | 50 | 100 | n.d.[f] |
[a] The reactions were performed in dichloromethane at room temperature with 1 equiv of vinyl ether (100 mm) 1 a–e and 2 equiv of tetrazine 2 a (200 mm) for 72 hours. [b] The reaction was complete after 40 hours. [c] Yield of isolated product. [d] The stability (as % of remaining starting compound) was assessed by HPLC in PBS pH 7.4 at 37 °C with a concentration of vinyl ether of 200 μm using acetophenone as an internal standard. [e] 10 % H2O in DMF. [f] 1 e does not absorb in the UV. n.d.=not determined.