Low Temperature Electronic Spectroscopic Observations on Light-Induced Cyclobutanone-Tetrahydrofurylidene Rearrangement
✍ Scribed by Prof. Dr. Gerhard Quinkert; Dipl.-Chem. Klaus H. Kaiser; Doz. Dr. Wolf-Dieter Stohrer
- Publisher
- John Wiley and Sons
- Year
- 1974
- Tongue
- English
- Weight
- 242 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0044-8249
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✦ Synopsis
diradicals the configuration-preserving effect of through-bond interaction is overcompensated[*] by the configuration-changing effect caused by formation of the ally1 system. The stereoisomers ( 9) and (1 0) were prepared by conventional methods and their configuration established non-empirically by NMR spectroscopy of suitable derivatives[''. UV irradiation of their methanolic solutions at room temperature yields a binary mixture of acetals in both cases. Chromic acid oxidation of the heterocyclic photoproduct ( 1 I), obtained from (91, affords exclusively (13) and that of the acetalic photoproduct (12), derived from ( l o ) , yields exclusively (14). The configuration of the two y-Iactones follows from the formation of(l.?)[together with (f5)] from ( 9 ) and of( 14) [in addition to ( I 6)] from (10) on Baeyer-Villiger oxidation. 0 CH3 (fl) H\ ,H C 0 Since the four-membered rings of both ( 9) and (10) are subject to stereospecific expansion and undergo neither configurational nor constitutional isomerization we conclude that the resulting "oxucarbenes""ol are formed directly from the electronically excited four-membered cyclic ketones und not via intermediate I ,4-alkyl/acyl diradicals.