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

✍ Scribed by 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

• Book ID: 104209431
• Publisher: Elsevier Science
• Year: 1999
• Tongue: French
• Weight: 721 KB
• Volume: 55
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(99)00351-8

✦ Synopsis

The Michael addition reactions of fl-nitrostyrenes 1 with 4-pentene-l-magnesium bromide 2a or 3-butene-l-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 tram-10:cis-10 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 chioroformate, 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 CO 2 (or EtOCO2H) to yield the final products.