Electroreduction of (1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol derivatives. Behaviour of electrogenerated species and applications to organic synthesis

Abstract

Hydroxylamines electrogenerated from (1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol derivatives (derivatives of p-nitrophenylserinol) are unstable in methanol-acetate buffer and practically stable in acetonitrile-aqueous acetate buffer. This latter medium was used to carry out subsequent reactions in situ involving the triacetylated p-hydroxylaminophenylserinol and various reagents. An azoxy compound was the major product isolated after reaction with maleic or phthalic anhydrides. In contrast, a benzoxazine dione was normally obtained with phthaloyl dichloride and a N-sulphonylated hydroxylamine was produced with p-toluenesulphonyl chloride.

Electrosynthesis of nitroso compounds from (1S, 2S)-2-amino-l-(4-nitrophenyl)-propane-1,3-diol derivatives

“…As previously reported [17], the cyclic voltammograms at a hanging mercury electrode or a glassy carbon electrode of nitro compounds 1a-11a in methanolacetate buffer were characteristic of nitroarenes in protic media: a reversible system attributed to nitrosohydroxylamine couple was observed at less cathodic potential after reduction of the nitro group to the hydroxylamino group and scan reversal. Consequently, the hydroxylamine intermediate appeared stable at the time scale (0.1 Vs )1 ) of the cyclic voltammetry.…”

“…Acetic acid 3-acetoxy-2-acetylamino-1-{4-[hydroxy-(toluene-4-sulfonyl)-amino]phenyl}-propyl ester 2c: The physical characteristics are similar to those of the product obtained by adding p-toluenesulphonyle chloride to the hydroxylamino derivative electrogenerated from the nitro compound 2a [17]. …”

“…In order to improve the yields of the isolated products, the -OH and -NH 2 groups of 1a Were protected by N)O 1 )O 3 triple acetylation leading to 2a [17]. In a similar way, acetic acid 4-nitrobenzyl ester 11a was prepared from 4-nitrobenzyl alcohol in order to compare the behavior of 2a with this simpler substrate.…”

“…Consequently, the hydroxylamine intermediate appeared stable at the time scale (0.1 Vs )1 ) of the cyclic voltammetry. But, at the long time scale of macroscale electrolysis at a planar electrode (mercury cathode), the phenylhydroxylamines electrogenerated from 1a-11a were relatively unstable in the presence of a methanolic solution [17].…”

“…After adding sodium p-toluene sulphinate in aqueous H 2 SO 4 to a methanolic solution of the nitroso compound, we observed an immediate change of the color and a disappearance of the cathodic wave which corresponds to the reduction of the nitroso group. N-Sulphonylated hydroxylamine 2c (scheme 5) was previously prepared by adding p-toluenesulphonyl chloride to the hydroxylamino derivative resulting from the cathodic reduction of the nitro compound 2a at a mercury cathode [17].…”