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Updated: Mar 18, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Single-Step Formation of Pyrimido[4,5-d]pyridazines by a Pyrimidine-Tetrazine Tandem Reaction
Juraj Galeta1, Michal Šála1, Martin Dračínský1
1Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nám. 2, 166 10 Prague, Czech Republic.
Abstract:
A straightforward synthesis of pyrimido[4,5-d]pyridazines from pyrimidines and tetrazines under basic conditions is reported. Deprotonated, substituted 5-halopyrimidines readily react with variously substituted tetrazines in a highly regioselective manner via a complex reaction pathway, which was supported by DFT calculations. This mechanism leads to the empirically observed regioisomers without going through the conceivable hetaryne intermediate. These results on 5-halopyrimidines led to development of the methodology for preparation of opposite regioisomers based on 6-halopyrimidines.
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