Ferrocelane/FerroTANE

Ferrocelane ligands were first reported by Mark Burk (Duke University) as 1,1’-ferrocene based equivalents of DuPHOS ligands. FerroTANE ligands were later reported essentially simultaneously by Marinetti (Paris) and Burk (then at Chirotech). The following lists reactions, organised by metal (Pd,  Rh, Ru, Ir, Co), for which the application of these ligands has resulted in >80% ee. ACE = Asymmetric Catalytic Efficiency.  Literature covered until end 2017 (11 entries).

Ferrocelane_FerroTANE

Palladium

Pd – C-P Coupling CC04-530

PP-FerrocTANE_CC04-530

 

JACS07-129-15122

PP-FerroTane_JACS07-129-15122

Absolute configuration of products not determined, but may possibly be inferred from CC04-530 as the reaction described also proceeds via an intermediate palladacycle, and assuming rapid  epimerisation (relative to reductive elimination) of intermediate Pd(II)-phosphide complexes mediated by Et-FerroTANE.

 

JACS13-135-16829

PP-Ferrocelane_JACS13-135-16829

Rhodium

Rh – Hydrogenation TL94-35-9363

PP-Ferrocelane_TL94-35-9363

Absolute configuration not stated but assigned as S by comparison to results in OL02-4-4471.

Angew00-39-1981

PP-FerroTane_Angew00-39-198

OPRD03-7-407

PP-Ferrocelane_OPRD03-7-407

These results were obtained during a screening and optimisation study on the asymmetric hydrogenation of 2-methylenesuccinamic acid. Catalyst [Rh(COD){(S,S)-Et-DuPHOS}]BF4 was further optimised to give R product in 96% ee and >98% conversion with S/C = 100000 : 1 provided the substrate was chloride free (ACE = 18750).

Angew03-42-913

PP-FerroTane_Angew03-42-913_1

Reaction times not stated but pseudo-first-order half-times given as between 0.5 (Ar = Ph) and 1.8 min (Ar – m-nitrophenyl). Catalyst loading  also reduced to 0.1 mol% but ee not stated. High activity possibly due to large P-Rh-P bite angle (98.3o – contrast with approx. 85o in corresponding DuPHOS complexes.

CEJ02-8-5196

PP-FerroTane_CEJ02-8-5196

Conversion/yield and reaction time not stated but pseudo-first-order half-time given as 1.2 min. Absolute configuration not stated and assigned tentatively by comparison to the above examples (i.e. Angew03-42-913).

CT08-137-11

PP-FerroTANE_CT08-137-11

Absolute configuration not stated and assigned by comparison to results reported in TL94-35-9363 and Angew00-39-1981 (described above). Reported ee an average of 32 simultaneous runs (using both enantiomers of the ligand) performed in a parallel high pressure microreactor.

Ruthenium

Ru – Hydrogenation EJIC03-2583

PP-FerroTane_EJIC03-2583

 

Iridium

Ir – [2 + 2 + 2] cycloaddition CC12-48-1311

PP-FerroTane_CC12-48-1311

 

Cobalt

Hydroboration – 1,6-enyne cyclisation JACS17-139-6526

Ferrocelane_JACS17-139-6526

The first scheme above is the result of a ligand scoping study for which (R,R)-QuinoxP was identified as the best ligand (under the same conditions the same enantiomer of the product was formed with a 49:1 chemoselectivity, 99% ee and 85% yield). Observed that N- and C-tethered enynes underwent hydroboration/cyclisation to alkyl boronate esters with Me-Ferrocelane as ligand in THF (2nd and 3rd schemes).