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Paper | Regular issue | Vol 45, No. 7, 1997, pp.1345-1361
Published online, 1st January, 1970
DOI: 10.3987/COM-97-7819
Synthesis of Aspirochlorine Precursors

Kuniaki Itoh,* Makoto Kasami, Rintaro Yamada, Toshiaki Kubo, Masahiro Honda, and Akira Sera

*Department of Chemistry, Faculty of Science, Kobe University, Nada-Ku, Kobe 6557-8501, Japan

Abstract

Synthesis of key precursors of aspirochlorine (1) and related compounds has been achived in 5 steps from 1,4-diacetyl-2,5-piperazinedione (2). MCPBA mediated oxidative cyclization of 1-acetyl-3-salicylidene-2,5-piperazinedione (4) yielded a spiro 3H-benzofuranol derivatives (6) stereoselectively. Bromination of 6 by a 2-fluoropyridinium salt and sodium bromide, followded by NBS treatment yielded dibromide mixtures (8). Conversion of produced dibromides (8) to dithioacetates (9) by potassium thioacetate afforded all of four possible diastereomers. The ratio of the diastereomers was found to be solvent dependent.