ORGN 641 |
| 3,6 Di(2 pyridyl)-pyridazines are interesting compounds since they can self-assemble with copper(I) ions into [2×2] grid-like metal complexes. Functionalized 3,6 di(2 pyridyl)-pyridazines can be synthesized via retro Diels-Alder reaction between 3,6 di(2 pyridyl)-1,2,4,5-tetrazine 1 and various acetylenes. To accelerate these retro Diels-Alder reactions, microwave irradiation was explored to quickly and efficiently heat the reaction mixtures. The retro Diels-Alder reaction with 5-hexyn-1-ol could be accelerated from 40 hours reflux in toluene to 30 minutes superheating in dichloromethane (150 ēC) under microwave irradiation. Surprisingly, it was found that microwave-irradiation of tetrazine 1 in acetone (150 ēC) resulted in the formation of 3,6 di(2 pyridyl)-4 methylpyridazine. The observed retro Diels-Alder reaction with acetone occurs presumably via the enol tautomer of acetone. The double bond of this 2-propenol can act as electron-rich dienophile in the inverse electron demand Diels-Alder reaction, which, after the loss of both a nitrogen and a water molecule, results in the formation of 3,6-di(2-pyridyl)-4-methyl-pyridazine 3 (Figure).
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Asymmetric Reactions, Heterocycles, Aromatics, Combinatorial, and Physical Organic Chemistry
8:00 PM-10:00 PM, Wednesday, 31 August 2005 Washington DC Convention Center -- Hall A, Poster
Division of Organic Chemistry |
