Electroreductive five- and six-membered cyclization of aromatic β- and γ-imino esters derived from (S)-aspartic acid and (S)-glutamic acid

The electroreduction of aromatic β-dimethylcarbamoyl-β-imino esters, prepared from (S)-aspartic acid, in the presence of chlorotrimethylsilane gave five-membered cyclized products, 1-benzoyl-4-hydroxy-5-aryl-N,N-dimethylpyrrolidine-2-carboxamides and 5-(dimethylcarbamoyl)-2-aryl-1H-pyrrol-3-yl benzoates, depending on the post-treatment after the electroreduction. The electroreduction of aromatic γ-dialkylcarbamoyl-γ-imino and γ-methoxylmethyl-γ-imino esters, prepared from (S)-glutamic acid, and following transformation gave six-membered cyclized products, 1-benzoyl-5-hydroxy-N,N-dialkyl-6-phenylpiperidine-2-carboxamides and 3-hydroxy-6-(methoxymethyl)-2-phenylpiperidin-1-yl)(phenyl)methanones, respectively.