Amino dehalogenation

The use of microwave irradiation for this reaction, compared to conventional thermal heating, was investigated. Chloroform used as solvent under the conventional heating did only allow a temperature of 60 °C and a direct comparison between the two methods is therefore somewhat unfair imder these circumstances. Nevertheless, the microwave-assisted method is attractive and proved useful for both primary and secondary amines resulting in highly substituted pyrazolo ring-fused pyridones 40 in 68-86% yields within only 10 min. 

Microwave-Assisted Substitution Reactions via Eiectrophiiic Reagents 3.3.1 

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As already indieated in Seetion III,A, nueleophilie attaek easily oeeurs at positions ortho and para to the ring nitrogen and/or the nitro group. Amino-dehalogenation in halogeno-3-nitronaphthyridines has been extensively studied and a number of amino-3-nitronaphthyridines (96l-96v) were obtained by the aetion of ethanolie ammonia on the 2- and 4-ehloro-3-nitronaphthyridines (96a-96k). 

Fig. 8 A comparison of the results from microwave and conventional heating for amino-dehalogenation on 2-pyridones...

As mentioned in Section II,D,l,a, the presence of a r-butyl or phenyl group at position 5 of the 1,2,4-triazine ring does not prevent addition of the amide ion to that position. Therefore, it becomes of interest to investigate whether in the amino-dehalogenation of two annelated 3-chloro-l,2,4-triazines, i.e., 3-chloro-l,2,4-benzotriazine (123) and 3-chlorophenanthro[9,10-e]l,2,4-triazine (125), using potassium amide/liquid ammonia, the Sn(ANRORC) process would be involved. Both compounds... 

A similar reaction is noted on treating the 3-(a-haloacylamino)-rhodamine (285) with a secondary alkylamine. Nucleophilic attack at the ring-carbonyl, with concomitant opening of the thiazolidine ring, rather than amino-dehalogenation at the acyl-side-chain, is followed by ring closure to the 4//-l,3,4-thiadiazin-5(6//)-one (286) (Equation (19)) <93AP(326)249>. 

The chapter The SN -Amination of Aromatic Compounds , authored by Anna Gulevskaya and Alexander Pozharsky (Rostov-on-Don University, Russia), presents a comprehensive review on the direct Sn amination of electron-deficient heteroaromatic compounds. Recent advances in this area and many new aspects of the Sn amination are discussed, including new types of reagents, metal-free catalysts, solvents and the hydride ion acceptors. The review shows that the amination is rather promising synthetic alternative to both classic and transition metal-catalyzed amino-dehalogenation reactions. 

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