One-pot synthesis of five- or six-membered carbocycles through intramolecular cycloadditions by the use of ethyl chloroformate

Ju Tsung Liu, Wen-Wei Lin, Jeong Jiunn Jang, Jing Yuan Liu, Ming Chung Yan, Chihua Hung, Kuo Hsi Kao, Yeh Wang, Ching-Fa Yao

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The Michael addition reactions of β-nitrostyrenes 1 with 4-pentene-1- magnesium bromide 2a or 3-butene-1-magnesium bromide 2b generated nitronates 3 or 4. Medium to high yields of isoxazolidine derivatives 9 and 10 were obtained when nitronates 3 or 4 were treated with ethyl chloroformate and catalytic amount of 4-dimethylaminopyridine (DMAP) at room temperature in one-pot and the ratios of trans-9:cis-9 were from 1:3.00 to 1:4.06 and the ratios of trans-10:cis-1 0 were >99:1. The formation of compounds 9 is proposed to proceed through intramolecular nitrile oxide-olefin cycloadditions (INOC) because compounds 14a-d, obtained from the trapping of the nitrile oxides by ethyl chloroformate, could be isolated. The mechanism of the generation of compounds 10 is proposed to proceed through intramolecular alkoxycarbonyl nitronate-olefin cycloadditions (IAOC) to form intermediates N-(ethoxycarbonyl)isoxazolidines 13 and then eliminate EtOH and CO2 (or EtOCO2H) to yield the final products.

Original languageEnglish
Pages (from-to)7115-7128
Number of pages14
Issue number23
Publication statusPublished - 1999 Jun 4


ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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