233606-27-4Relevant academic research and scientific papers
One-pot synthesis of five- or six-membered carbocycles through intramolecular cycloadditions by the use of ethyl chloroformate
Liu, Ju-Tsung,Lin, Wen-Wei,Jang, Jeong-Jiunn,Liu, Jing-Yuan,Yan, Ming-Chung,Hung, Chihua,Kao, Kuo-Hsi,Wang, Yeh,Yao, Ching-Fa
, p. 7115 - 7128 (1999)
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.
