A new method for the synthesis of 2-chloro-2-nitrocarboxylic esters from 2-nitrocarboxylates is described. The procedure consists of the oxidative chlorination of titanium(IV) enolates of 2-nitro esters in the presence of ammonium nitrate. Esters of 2-chloro-2-nitrocarboxylic acids are formed in very good to quantitative yields. Application of this method for the chlorination of $\alpha$,$\alpha$′-dinitrodicarboxylates leads to $\alpha$,$\alpha$′-dichloro-$\alpha$,$\alpha$′-dinitrocarboxylic esters with high meso-diastereoselectivity. The absence of ammonium nitrate from the reaction mixture affects the reduction of nitro groups and leads to partial transformation of 2-nitrocarboxylic esters into 2-(hydroxyimino)carboxylates.
keywords in English:
oxidative chlorination, diastereoselectivity, titanium enolates, esters, transition states
departmental parameterization:
30
affiliation:
Wydział Chemii : Zakład Krystalochemii i Krystalofizyki, Wydział Chemii : Zakład Chemii Organicznej