94993-19-8Relevant academic research and scientific papers
Possible formation of rhenabenzene. Lithium-halogen exchange reactions in η1-4-bromo-1,4-diphenyl-1,3-butadienyl ligands to form rhenabenzene and ferrabenzene
Ferede, Roman,Hinton, James F.,Korfmacher,Freeman,Allison, Neil T.
, p. 614 - 616 (2008/10/08)
Introduction of (E,E)-1,4-dilithio-1,4-diphenyl-1,3-butadiene (1) to (CO)4PPh3ReBr followed by protonation or methylation give (1,3-diphenyl-2-hydroxy-cyclopentadienyl)tricarbonylrhenium (5a) and (1,3-diphenyl-2-methoxycyclopentadienyl)tricarbonylrhenium (5b), respectively. A mechanism consistent with generation of 5 involves formation of an anionic acyl intermediate followed by alkyl migration to give (η1-4-lithio-1,4-diphenyl-1,3-butadienyl)rhenium complex 7. Cyclization by attack on a terminal carbonyl by the alkenyllithium moiety generates rhenabenzene 8 from 7. Reductive elimination, loss of triphenylphosphine, and protonation or methylation give 5a or 5b, respectively. A second synthetic approach to 8 is described. Preparation of (η1-4-bromo-1,4-diphenyl-1,3-butadienyl)rhenium complex 10 is reported. Lithium-halogen exchange with 10 using n-butyllithium gives 7. Intermediate 7 may convert to 5 as described above. Preparation of (η1-4-bromo-1,4-diphenyl-1,3-butadienyl)iron complex 11 is also reported. Lithium-halogen exchange and cyclization form an unstable ferrabenzene. Reductive elimination, loss of a terminal carbonyl, and methylation give 1,3-diphenyl-2-methoxyferrocene (4).
