In:
Recueil des Travaux Chimiques des Pays-Bas, Wiley, Vol. 114, No. 11-12 ( 1995-01), p. 480-482
Abstract:
3‐Alkyl‐4‐phenoxybut‐1‐enes (alkyl: methyl, isopropyl, tert ‐butyl) on excitation at 254 nm in cyclohexane give rise to 4‐alkyl‐2‐oxatetracyclo[5.4.0.0 1,8 .0 5,11 ]undec‐ 9‐enes via intramolecular meta photocycloaddition. Prevailing stereochemical features are the configuration of the alkyl group at C‐4 and the conformation of the tetrahydropyran ring contained in the tetracyclic system. These are revealed by detailed 1 H‐NMR analysis and interpretation of the coupling constants. Whereas the alkyl group at C‐4 invariably occurs in the exo configuration, the conformation of the tetrahydropyran ring depends on the bulkiness of the alkyl substituent. Thus, the C‐4 methyl group occupies an equatorial position in a chair conformation, while a flattened chair conformation accomodates appropriately the C‐4 isopropyl group in the pertaining structure. The required equatorial position of the tert ‐butyl group at C‐4, on the other hand, forces the tetrahydropyran ring into a boat conformation, thereby alleviating steric constraints.
Type of Medium:
Online Resource
ISSN:
0165-0513
,
0165-0513
DOI:
10.1002/recl.v114:11/12
DOI:
10.1002/recl.19951141110
Language:
English
Publisher:
Wiley
Publication Date:
1995
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