On the Fluorescence Reaction of Pharmaceutically Important o ‐Aminobenzamides and o ‐Aminobenzenesulfonamides with Phthalaldehyde and Analogues

In order to develop a specific TLC‐fluorescence detection, drugs such as Quinethazone ( 1a ), Fenquizone ( 1b ), Diazoxide ( 7 ), Bendroflumethiazide ( 11a ), Hydrochlorothiazide ( 11b ) and their derivatives were hydrolysed to provide o ‐aminobenzamide 2 and o ‐aminobenzenesulfonamides 8, 12 , and 13 . The reaction of these 1,5‐ N ‐bisnucleophiles with phthalaldehyde ( 3a ) and analogues 3b – e resulted in weak up to intensive fluorescent products 5, 9, 14, 15 , Applying this method to Diazoxide capsules, 5 ng of Diazoxide ( 7 ) could be detected by pre‐ and postchromatographic derivatisation with 3‐benzoylpyridine‐2‐carbaldehyde ( 3e ) on TLC plates. The reaction of o ‐aminobenzenesulfonamide 8 with 3,4‐dimethoxyphthalaldehyde ( 3b ) in CD 3 OD/DCI provided a monodeuterated compound 10b , N , N ‐Acetals 17,18 , and 19 were obtained from the reaction of furan‐3,4‐dicarbaldehyde ( 16 ) with o ‐aminobenzenesulfonamides 8, 12 , and 13 in MeOH/20°C.