Active hydrogen with diazonium

Free-radical addition of an aryl group and a hydrogen has been achieved by treatment of activated alkenes with a diazonium salt and TiCls. ... 

Diazonium groups react with active hydrogen sites on aromatic rings to give covalent diazo bonds. Generation of a diazonium functional group usually is done from an aromatic amine... 

In the case of active methinyl compounds, which, of course, lack the necessary mobile hydrogen, coupling with diazonium salts results in azo compounds. 

Amino-3-pyrazolin-5-ones (4-imino-3-pyrazolidinones) react with nitrous acid as do ordinary aromatic amines to form diazonium salts.426,984,1353 These then couple readily with aromatic amines,1017,1018,1060 phenols992,1323 and aliphatic compounds having active hydrogen atoms,428,1017 such as acetoacetic esters. The products are 4-azo-3-pyrazolin-5-ones (eq. 200). The diazonium salts also couple... 

These agents would be used as adjuncts to beta lactams since they have no antibacterial activity in their own right. A key reaction in the synthesis of each compound involves the replacement of the amine at 6 and the protection of that position as a mono- or di-halide. Thus reaction of 6-APA (2-4) with nitrous acid gives the diazonium salt (9-1) this is converted to the dibromide (9-2) on treatment with bromine. The ring sulfur is then oxidized with permanganate to the sulfone (9-3). Hydrogenolysis of the product replaces the two bromine atoms by hydrogen to afford sulbactam (9-4) [13]. 

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