Active hydrogen diazonium reaction

Diazonium groups react with active hydrogens on aromatic rings to give covalent diazo bonds. Generation of a diazonium-reactive group usually is done from an aromatic amine by reaction... 

More than one mechanism has been proposed to explain the catalytic activity of diazonium salts in initiating polymerization of cyclic ethers. Dreyfuss and Dreyfuss (1 ) postulated that initiation involves hydrogen abstraction from the cyclic ether by a carbenium ion formed via decomposition of the diazonium salt, followed by polymerization via tertiary oxonium ions associated with PFe" counterions. The polymerization reactions studied by Dreyfuss and Dreyfuss were initiated by thermal decomposition of... 

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]. 

Diazonium salts can be prepared directly by replacement of an aromatic hydrogen without the necessity of going through the amino group.136 The reaction is essentially limited to active substrates (amines and phenols), since otherwise poor yields are obtained. Since the reagents and the substrate are the same as in reaction 1-3, the first species formed is the nitroso compound. In the presence of excess nitrous acid, this is converted to the diazonium... 

In contrast to classical Meerwein arylations, non-activated alkenes are well suited for this reaction type for two reasons. First, due to the relatively slow formation of azo compounds by addition of aryl radical 49 to 48, this undesired pathway cannot compete successfully with the attack of 49 on the alkene to give radical adduct 50. Second, a nucleophilic alkyl radical 50 arises from the addition step, which is effectively trapped by electrophilic salt 48 to give azo compound 51. As a result of several improvements, the methodology is now applicable for a wide range of polar to non-polar alkenes with almost no restrictions on the substitution pattern of the diazonium salt [101, 102]. Moderate diastereoselectivities have been obtained in first attempts with chiral auxiliaries [103]. The azo compounds accessible, such as 51, can be converted to carboamination products 52 by hydrogenation and to various other heterocycles. 

Diazonium salts (157) (Equation (1)) have been reacted with 2-chloro- 1,3-dicarbonyl compounds yielding heterocycles (158) (50-75%) <82JCS(Pl)989>. In a similar reaction sequence (Scheme 3), salt (157) yielded products (160) and/or (161) with activated methylene compounds <89ZN(B)95i>. The formation of compound (160) involves elimination of a molecule XH, which is usually hydrogen cyanide. 

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