From Rings with an Endocyclic Keto Group Adjacent to a Replaceable Hydrogen Atom

From Rings with an Endocyclic Keto Group Adjacent to a Replaceable Hydrogen Atom 

Similarly, eighteen l,3-diamino-5,6-dihydrobenzo[/]quinazolines (e.g., 32) were made by fusion of 2-tetralones (e.g., 31) with cyanoguanidine Average conditions were 190°-210°C (internal) for 30 mins. Yields ranged between low and good.16 

More difficult to explain is the production of l,3-diphenyl-5,6,7,8-tetra-hydroquinazoline-2,4-dithione (33) by heating cyclohexanone with N,N -diphenylthiourea at 150°C (poor yield).17 

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