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Short Paper | Special issue | Vol 97, No. 2, 2018, pp.1257-1268
Published online, 29th May, 2018
DOI: 10.3987/COM-18-S(T)82
Efficient Synthesis of t-Butyl 3-Alkyl-N-hydroxyoxindole-3-carboxylates from Di-t-butyl 2-nitrophenylmalonates

Yu-suke Yamai, Kyoji Ishida, Itaru Natsutani, Shinichi Uesato, Yasuo Nagaoka, and Takaaki Sumiyoshi*

*Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680, Japan

Abstract

A selective and efficient synthesis of t-butyl 3-alkyl-N-hydroxy- oxindole-3-carboxylates from di-t-butyl 2-nitrophenylmalonates is described. A tandem reduction-cyclization approach involving reduction of di-t-butyl 2-methyl-(2-nitrophenyl)malonate to di-t-butyl 2-(2-(hydroxyamino)phenyl)-2-methylmalonate followed by accelerated cyclization reaction using a combination of Rh/C and hydrazine monohydrate smoothly and selectively afforded the N-hydroxy-oxindole scaffold. This methodology was successfully applied to gram-scale-synthesis of the t-butyl N-hydroxy-3-methyl-oxindole-3-carboxylate 1 without silica gel column chromatographic separation step.