Benzothiazoles aromatic nucleophilic substitution

An intramolecular aromatic nucleophilic substitution has been used for the preparation of 2-substituted benzothiazoles (388) in high yields from o-halothioanilides (387), the halogen atoms being iodine, bromide, or chlorine <82TL5093>. This reaction can also be carried out with naphtho-derivatives <89ijc(B)597>. Moreover, in the presence of sodium carbonate, the reaction can be extended to fluorine-substituted substrates (Equation (81)) <89JHC1039>. 

The ecofriendly solvent-free reactions of o-aminothiophenol and aromatic or aliphatic P-keto esters with microwave irradiation produced 2-substituted benzothia-zoles in excellent yields. The formation of the 2-substituted benzothiazoles probably involves the nucleophilic addition of the thiol group to the keto group of the P-keto ester followed by elimination of ethyl acetate from the resulting adduct. Then it undergoes an intramolecular addition of the o-amino group to the carbonyl group to give an adduct, from which water is eliminated to afford the 2- substituted benzothiazoles (Kamila et al., 2005). 

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