1,3-Dipolar Cycloaddition of Benzonitrile Oxide to Substituted 4,5-Dihydro-3-methylene-2(3H)-furanones

✍ Scribed by Štverková, Slávka ;Žák, Zdirad ;Jonas, Jaroslav

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 462 KB
• Volume: 1993
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.1993199301189

✦ Synopsis

Abstract

Benzonitrile oxide cycloadds to the CC bond of substituted 4,5‐dihydro‐3‐methylene‐2(3__H__)‐furanones 1a–1g. Thus, (E)‐1a and (E)‐1b are converted into the corresponding isoxazolinespirodihydrofuranones (4__RS__,5__RS__)‐2a and (4__RS__,5__RS__)‐2b, and (E)‐1c is converted into a mixture of isomers (4__RS__,5__RS__)‐2c and (4__RS__,5__RS__)‐3c. The reactions of (E)‐1d–1g yield mixtures of the corresponding diastereomeric isoxazolinespirodihydrofuranones (4__RS__,5__RS__,8__RS__)‐2d and (4__RS__,5__RS__,8__SR__)‐2d, (4__RS__,5__RS__)‐3e and (4__RS__,5__SR__)‐3e, (4__RS__,5__RS__)‐3f and (4__RS__,5__SR__)‐3f, (4__RS__,5__RS__)‐3g and (4__RS__,5__SR__)‐3g. The addition of benzonitrile oxide to (Z)‐1a gives (4__RS__,5__SR__)‐2a and 4a. In the cycloaddition with (E)‐1a the p‐tolylsulfonyloxy group in the intermediate (4__RS__,5__RS__)‐2a is partially replaced by chlorine to give (4__RS__,5__RS__)‐2h. – The structures of (4__RS__,5__RS__)‐2h, (4__RS__,5__RS__)‐3e, (4__RS__,5__SR__)‐3e, and 4a are determined by X‐ray analysis. The ^1^H‐ and ^13^C‐NMR spectra of the products are discussed and the reaction course is rationalized on the basis of HOMO‐LUMO energy gaps.