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Oxidative Coupling Of 2‐Alkyl‐6,6‐dimethylpentafulvenyl Anions
Author(s) -
You Shaochun,
Neuenschwander Markus
Publication year - 1993
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.19930760411
Subject(s) - chemistry , isomerization , steric effects , intermolecular force , oxidative coupling of methane , coupling (piping) , ion , photochemistry , computational chemistry , stereochemistry , medicinal chemistry , catalysis , molecule , organic chemistry , mechanical engineering , engineering
Cucl 2 ‐Induced oxidative coupling of 2‐( tert ‐butyl)‐6,6‐dimethylpentafulvenyl anion 9 predominantly takes place at C(7) and C(5) to give [7–7] and [7–5] coupling products 15 and 16 in 35 and 47% yields, respectively ( Scheme 3 ) whose structures are elucidated from 1D‐ and 2D‐NMR analysis. Compared with the product distribution observed for 6,6‐dimethylpentafulvenyl anion 2 ( Scheme 1 ), no coupling at C(2)/C(3) of 9 is observed. This means that, besides electronic effects, steric effect are also important in oxidative couplings of fulvenyl anions. The same couplings occur in the case of 2,3‐bis(6,6‐dimethylfulven‐2‐yl)‐2,3‐dimethylbutane dianion 10 as well but, due to electronic as well as conformational effects ( Scheme 5 ), intermolecular coupling (to give polymers 17 , Scheme 4 ) is strongly favored over intermolecular coupling. Mechanisms explaining base‐catalyzed isomerization 15a ⇄ 15b ⇄ 15c ( Scheme 6 ) as well as isomerization 16a ⇄ 16b ( Scheme 7 ) are proposed.