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Azo Bridges from Azines, XIX. Intramolecular \documentclass{article}\pagestyle{empty}\begin{document}$ \left[ {\sigma _{\rm s}^2 + \pi _{\rm s}^2 } \right] $\end{document} Photocycloaddition Reaction of Parallel Three‐Membered Rings with Azo Groups
Author(s) -
Hünig Siegfried,
Schmitt Michael
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960418
Subject(s) - chemistry , intramolecular force , nucleophile , aziridine , methanol , ring (chemistry) , medicinal chemistry , crystallography , stereochemistry , catalysis , organic chemistry
[3 + 2] Photocycloaddition reaction of three‐membered rings with azo groups were accomplished for the first time by photochemically induced π,π* excitation of several systems of the general type C E exemplified by 1 , 3 , 5 , 7 , 10 , 13 , and 17 . Intramolecular reaction of the parallel arranged functional groups yields cage compounds F H ( 2 , 4 , 6 , 8 , 11 , 14 , and 18 ) in a [σ s 2 + π s 2 ] process, Systems C E are inert on n,π* excitation in aprotic solvents. In methanol or better 2‐propanol, however, the azo groups are reduced from their triplet states. The resulting hydrazino groups, also available by catalytic hydrogenation, open the aziridine rings of 7 , 10 , and 13 as well as the oxirane ring of 17 by nucleophilic attack, producing the half cages 9 , 12 , and 19 .