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Photochemische Cycloadditionen von 3-phenyl-2h-azirinen mit Aldehyden. 31. Mitteilung über Photoreaktionen

✍ Scribed by Heinz Giezendanner; Heinz Heimgartner; Barry Jackson; Tammo Winkler; Hans-Jürgen Hansen; Hans Schmid

Publisher
John Wiley and Sons
Year
1973
Tongue
German
Weight
860 KB
Volume
56
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

Experiments concerning the photochemical condensation of 3‐phenyl‐2__H__‐azirines 1 with aliphatic and aromatic aldehydes to 3‐oxazolines 4 are fully described (cf. scheme 1). Photochemically nitrile methylides of type 2 are first formed, which then very quickly react thermally with the aldehydes in a regiospecific manner to give the 3‐oxazolines 4. Azirines monosubstituted in position 2 (lb and 1c) give mixtures of cis, trans‐oxazoline isomers, in which the cis isomer predominates. The stereoselectivity of the cycloaddition reaction can be rationalized by a simple model (scheme 10).

The stereoisomeric 3‐oxazolines 4 are distinguishable in the NMR. spectra by the large homoallylic coupling constants between the H atoms on C(2) and C(5).

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