Tetrahydroquinoline bromination

Two modifications of the well-known benzothiazole preparation have been employed to prepare unusual heteropoly cycles. Konig et al.ils treated l-thiocarbamoyl-l,2,3,4-tetrahydroquinoline (236) with bromine in chloroform to give the thiazolo[3,4,5-J,i]quinoline derivative 237. In a process which requires disruption of the resonance stabilization of the pyridine ring, Harris416 reported that treatment of l-(2-pyridyl)-2-thiourcas with sulfuryl chloride or with bromine gives the hydrohalide salts of 2-imino-2//-[l,2,4]thiadiazolo[2,3-a]pyridines (238). 

Carbon-sulfur bond formation by oxidative cyclization of a thiourea derivative using bromine will in the case of (521) furnish a thiazolo[/,/]quinoline (522 Z = NH). The same imine is obtained from 8-mercapto-l,2,3,4-tetrahydroquinoline on treatment with cyanogen bromide with phosgene the 2-oxo derivative (522 Z = 0) is formed (63JOC2581). 

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