Pyrrolo pyridazine, 4-phenyl

H(22)2269]. In fact, compound 170e coupled with the activated phenyl to give the pyrrolo[3,2-c]cinnoline 173, while compound Ic still coupled with the 4-position to give the pyrrolo-pyridazine 169c. 

The synthesis of pyrrolo[2,3- 7 pyridazines can be achieved by starting either with pyridazine, a tetrazine, or a pyrrole. Pyridazinone 80 reacts with bromomethyl derivatives to give poor yields of 81 <1996H(43)1863> (Equation 34), while 5-acetyl-2-methyl-4-nitro-6-phenyl-3(2//)-pyridazinone, after treatment with sarcosine ethyl ester for a brief time at room temperature, followed by acid hydrolysis afforded a good yield of 82 (70%) <1994S669>. 

Ring enlargement of 5-hydroxy-6-phenyl-5//-pyrrolo[3,4-6]pyridin-7(6//)-one occurs in refluxing hydrazine hydrate to give a 63% yield of pyrido[2,3-d]pyridazin-8(7//)-one (7).154... 

A soln. of startg. azoalkene in toluene refluxed under N2 for 3 h 2-(2,4-dinitro-phenyl)-4,7-dimethyl-1,2,4a,7a-tetrahydrofuro[3,4- pyridazin-5(7//)-one. Y 67%. This reaction proceeds with complete stereoselectivity to give the cw-fused adduct under kinetic control. F.e. and pyrrolo-analogs s. T.L. Gilchrist et al., J. Chem. Soc. Perkin Trans. I 1989, 353-9. 

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