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Intramolecular azide cycloaddition to a photochemically generated zwitterion

✍ Scribed by Arthur G. Schultz; Sun Ok Myong; Salvador Puig

Publisher
Elsevier Science
Year
1984
Tongue
French
Weight
251 KB
Volume
25
Category
Article
ISSN
0040-4039

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✦ Synopsis

Photochemical rearrangements of 2,5-cyclohexadienones 7a and 7b to bridged --llb via zwitterions 10a and lob are described. ----Photorearrangements of 2,5-cyclohexadienones, L, generally occur from triazenes lla and the n + V* excited triplet state.' Reorganization of electrons gives zwitterion 2, from which a [1,4] sigmatropic shift produces bicyclo[3.l.O]hex-3-en-2-one 2. Solvent* and diene trapping3y4 studies with 4-methyl-4-trichloromethylcyclohexa-2,5-dienone provide direct experimental evidence for the involvement of zwitterionsS of type 2, as originally postulated by Zimmerman and Schuster.6 8icyclo[3.l.O]hexenones 2 undergo secondary photorearrangements to give phenolic compounds and derivatives of diene ketenes. 1 Products from these rearrangements are dependent hv hv(b) J 3 hv(a) 1

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