Quinoline ring, 4-mercapto

F. Quinolines Carrying a Mercapto Group on the Benzo Ring, 400... 

UV and pKa measurements show that pyridine-3-thiol and quinoline-3-thiol occur predominantly in the zwitterion form, e.g. (133) (76AHC(S1)144). Quinolines carrying a mercapto group on the benzo ring exist in the zwitterion or the zwitterion extended quinone form to a larger extent than do the analogous hydroxy compounds (63AHC(S1)400). 

Examples of ring closures with c-amino mercapto heterocyclic compounds are the reactions of carbon disulfide with o-amino mercapto pyridines and o-amino mercapto quinolines, which respectively yield dihydrothiazolo pyridine-2-thiones and dihydrothiazolo qumohne-2-thiones. A summary of these compounds are 7 ... 

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