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Diels‐Alder Reactions of Tetradehydrodianthracene with Electron‐Rich Dienes
Author(s) -
Kammermeier Stefan,
Neumann Helfried,
Hampel Frank,
Herges Rainer
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.199619961113
Subject(s) - chemistry , cycloaddition , intramolecular force , cyclopentadiene , diradical , double bond , adduct , reactivity (psychology) , diene , sigmatropic reaction , medicinal chemistry , photochemistry , stereochemistry , organic chemistry , catalysis , natural rubber , medicine , physics , alternative medicine , pathology , nuclear physics , singlet state , excited state
Tetradehydrodianthracene (TDDA; 1 ) reacts with electronrich dienes such as butadiene, cyclopentadiene and o ‐quinodimethane under ambient conditions. Only 1:1 products 5–8 were observed even with a large excess of the diene and under drastic conditions (though two strained and highly pyramidalized double bonds are available). The enhanced reactivity of TDDA compared with its mono Diels‐Alder adducts is mainly due to the through‐bond and through‐space interaction of the two olefinic double bonds. During the cycloaddition one of the olefinic bonds in TDDA is converted into an extremely long C–C single bond (> 1.65 Å). Attempts to cleave the strained π‐bond thermochemically to form a diradical 13 afforded product 14a that was formed via a formal intramolecular homo 1,3‐sigmatropic shift.