Dihydro Derivatives without a Carbonyl Group in the Ring

3 Dihydro Derivatives Without a Carbonyl Group in the Ring 

While dihydropyridazines which can be oxidized to the aromatic system usually react rapidly with oxygen in solution to give pyridazines, presumably by addition of oxygen, hydroperoxide 

5-Phenyl-5,6-dihydrobenzo[c]cinnoline can be arylated by nucleophilic displacement of activated aryl halides to give what is essentially a tetrasubstituted hydrazine 85AG(E)596 . 

Oxidation of adjacent enantiomeric piperazic acids in the cyclic peptide (88) with air or hypochlorite (89MI 601-01 gave the corresponding peptide containing two 2,3,4,5-tetrahydropyridazine- 

6-tetrahydropyridazine derivatives (92), prepared by reaction of a-halogeno semi- 

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