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The Photochemical Synthesis and Denitrogenation of 8,9‐diazadibenzo[ c , e ]isobullvalene
Author(s) -
Burger Ulrich,
Mentha Yves G.,
Millasson Patricia,
Lottaz PierreAndré,
Mareda Jiri
Publication year - 1989
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19890720809
Subject(s) - chemistry , diradical , photochemistry , photodissociation , phenanthrene , medicinal chemistry , thermal decomposition , cyclooctene , peroxide , stereochemistry , organic chemistry , singlet state , catalysis , physics , nuclear physics , excited state
Starting from dibenzo[ a , c ]cyclooctene ( 4 ) and 4‐methyl‐3 H ‐1,2,4‐triazol‐3,5(4 H )‐dione (MTAD), the strained skeleton of the title azo compound 1 is assembled in a tandem photo‐ Diels ‐ Alder addition/di‐π‐methane rearrangement sequence. The synthesis is completed by a stepwise hydrolytic oxidation of the ensuing triazolidine‐dione 2 with nickel peroxide. Thermolysis of 1 in benzene solution is shown to be governed by an initial 1,3‐dipolar cycloreversion which leads, via an intermediate diazo compound 11 , to cyclobuta[ 1 ]phenanthrene 8 and two further carbene‐derived C 16 H 12 products. Photolysis of 1 at 350 nm leads in modest yield (12%), via a diazenyl diradical, to an unstable bridged bicyclobutane 10 (dibenzooctavalene). MNDO calculations suggest the latter to have a rapidly inverting, twisted structure of C 2 symmetry.