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A Variation of Titanium-Induced Carbonyl Coupling – Synthesis and Conformations of Terfluorenyl

✍ Scribed by Sergey Pogodin; Shmuel Cohen; Israel Agranat

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
296 KB
Volume
1999
Category
Article
ISSN
1434-193X

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✦ Synopsis

Reaction of fluorenone (4) with a low-valent titanium reagent central ring, and two equally folded side moieties with dihedral angles of 58.1°and 58.0°between the central and generated from TiCl 4 and Zn in THF in the presence of pyridine gave terfluorenyl (6) in 71% yield, bifluorenylidene side five-membered rings. The AM1 and PM3 calculations showed C 2 global minima, similar to the conformation in the (2), the conventional McMurry reaction product, in 2% yield, and additional reduction products. The reductive crystal. The calculated C s transition state conformations were found to be 21.3 (AM1) and 19.9 (PM3) kcal/mol higher in "trimerization" was rationalized in terms of an attack of the intermediate fluorenone dianion on bifluorenylidene. The energy than the global C 2 minima. A 2D-NMR NOESY experiment on 6 supported the C 2 (+sc,+sc) or C 2 (-sc,-sc) molecular structure of a single crystal of 6 indicated an approximately C 2 conformation, with a slightly twisted conformation in solution.

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