502995-02-0Relevant academic research and scientific papers
Enantioselective functionalisation of the C-2′ position of 1,2,3,4,5-pentamethylazaferrocene via sparteine mediated lithiation: Potential new ligands for asymmetric catalysis
Anderson, James C.,Osborne, James D.,Woltering, Thomas J.
, p. 330 - 339 (2008/10/09)
The s-BuLi-sparteine base combination deprotonated the C-2′ position of 1,2,3,4,5-pentamethylazaferrocene 1 and subsequent reaction with a range of electrophiles gave C-2 substituted products in 76-93% yield and ～80% ee. The products could be recrystallised to enrich ee's to >90%. Resubjection of the initial addition products (～80% ee) to the deprotonation conditions led to a kinetic resolution to give products with >90% ee and superior overall yields compared to recrystallisation for the cases where the electrophiles were Ph2CO, MeI and Ph2S2. Transmetallation of the 2-lithiopentamethylazaferrocene (～80% ee) with ZnCl2 allowed palladium catalysed cross coupling with a variety of C-2 haloaryl, heteroaryl and vinyl groups to give some novel C-2′ substituted pentamethylazaferrocene derivatives in 61-77% yield in 80% ee. Potential N,N-chelate ligands were recrystallised to >95% ee. A novel C 2-symmetric bis-pentamethylazaferrocene 10 could be synthesised by an iron catalysed oxidative coupling of the enatioenriched C-2 lithio derivative and in the presence of a PhMe-Et2O solvent mixture proceeded in 97% ee. This journal is The Royal Society of Chemistry.
