Microwave-Assisted Synthesis of 3,6-Di(pyridin-2-yl)pyridazines: Unexpected Ketone and Aldehyde Cycloadditions

Hoogenboom, Richard; Moore, Brian C.; Schubert, Ulrich S.

Abstract:

3,6-Di(pyridin-2-yl)pyridazines are an interesting class of compounds because of their metal-coordinating ability resulting in the self-assembly into [22] gridlike metal complexes with copper(I) or silver(I) ions. These and other substituted pyridazines can be prepared by the inverse-electron-demand Diels- Alder reactions between acetylenes and 1,2,4,5-tetrazines. In this contribution, the effect of (superheated) microwave conditions on these generally slow cycloadditions is described. The cycloaddition of acetylenes to 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine could be accelerated from several days reflux in toluene or N,Ndimethylformamide to several hours in dichloromethane at 150 °C. In addition, the unexpected cycloaddition of the enol tautomers of various ketones and aldehydes to 3,6-di(pyridin-2-yl)-1,2,4,5- tetrazine is described in detail providing an alternative route for the synthesis of (substituted) pyridazines.

Year:

2006

Type of Publication:

Article

Journal:

Journal of Organic Chemistry

Volume:

71

Pages:

4903 - 1909