Compounds containing Three or Four Fused Heterocyclic Rings 5,5,5 , 5,5,6 , 5,5,7 , 5,6,7 , and

Several ingenious syntheses of cyclazines have been carried out by Flitsch and his colleagues. The pyrrolopyrrolidone (870) is converted into the salt (871) by 

Fusion of 2-fluoroimidazole yields the tri-imidazolotriazine (879) if 4-substi-tuted 2-fluoroimidazoles are employed, mixtures of three of the four possible isomeric products are formed. 

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