Novel photocycloadditions of electron-deficient nitrones to 2-methyl-2-butene

✍ Scribed by Sehgal, R. K. ;Griffin, G. W.

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 504 KB
• Volume: 1991
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199119910194

✦ Synopsis

Abstract

In Order to decrease the ground state reactivity and increase their potential for [3+2] cycloadditions, cyano‐ and methoxy‐carbonyl‐substituted nitrones 1a and 1b, respectively, were prepared and irradiated in the presence of electron‐rich alkenes such as 2 to afford the corresponding oxazolidines in which th oxygen atom becomes attached to the least substituted terminus of the olefin and nitrogen attaches to the more highly substituted counterpart. While the oxazolidines 12a and 12b obtained from 1b, via the intermediacy of oxaziridine(s) 15 and subsequent NO bond scission, are isolated and characterized, the oxazolidin(s) 18 formed bny cyclization of 1a are more labile and may undergo ionization to the stabilized oxazolinium ion 19 followed by nucleophilic attack by cyanide ion with accompanying ring opening to afford 6. A sequential diradical mechanism is proposed to rationalize the formation of the observed photoproducts 5 and 6.