Synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (1-Oxa-2,7,8-triazaspiro[4,4]-2,8-dien-6-ones) via 1,3-dipolar cycloaddition and cycloelimination

Robert E. Sammelson, Chamindra D. Gurusinghe, Jeffrey M. Kurth, Marilyn M. Olmstead, Mark J. Kurth

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

An efficient and selective method for the synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (C) is reported. The process consists of utilizing the Baylis - Hillman reaction - or a quicker, stepwise MAC procedure - to give I followed by 1,3-dipolar cycloaddition and Swern oxidation to give β-ketoesters H, which were condensed with hydrazine derivatives to provide hydrazones that underwent cycloelimination. These novel spiro-fused (C5)-isoxazolino-(C4)-pyrazolones were confirmed by spectroscopic analysis as well as single-crystal X-ray of 5. We also concluded that all condensations/cycloeliminations, except with hydrazine itself, were more effective with catalysts or higher reaction temperatures. For example, TiCl4 was an efficient catalyst for hydrazone formation and cycloelimination with methylhydrazine, while phenyl-, benzyl-, and (4-methoxyphenyl)hydrazine reacted effectively without catalyst in refiuxing xylene.

Original languageEnglish (US)
Pages (from-to)876-882
Number of pages7
JournalJournal of Organic Chemistry
Volume67
Issue number3
DOIs
StatePublished - Feb 8 2002

ASJC Scopus subject areas

  • Organic Chemistry

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