New [5]ferrocenophane diphosphine ligands for Pd-catalyzed allylic substitution

New [5]ferrocenophane based diphosphine ligands, having planar and central chirality, were prepared. The stereogenic center was generated by the enantioselective CBS-reduction of [5]ferrocenophan-1-one. The straightforward transformation of hydroxyl group to dimethylamino group afforded amine 7, which was diastereoselectively ortho-lithiated and reacted with ClPPh2 to introduce planar chirality. The structure of the diphosphine 1 was elucidated by X-ray crystallography. The ligand was successfully applied to Pd-catalyzed allylic alkylation (91% ee).

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(R)-1,1′-(1-Hydroxypentan-1,5-diyl)ferroceneC15H18FeO[α]D = −27 (c 0.5, CHCl3)Source of chirality: enantioselective CBS-reductionAbsolute configuration: R

(R,pR)-1-(Diphenylphosphanyl)-2,1′-[1-(diphenylphosphanyl)pentan-1,5-diyl]ferroceneC39H36FeP2[α]D = +482.9 (c 0.31, CHCl3)Source of chirality: stereoselective synthesisAbsolute configuration: RpR

(R,pR)-1-(Diphenylphosphanyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]-3-trimethylsilylferroceneC32H40FeNPSi[α]D = +319.8 (c 0.54, MeOH)Source of chirality: stereoselective synthesisAbsolute configuration: RpR

(R,pS)-1-(Trimethylsilyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]ferroceneC20H31FeNSi[α]D = −113.3 (c 0.92, MeOH)Source of chirality: stereoselective synthesisAbsolute configuration: RpS

(R,pS)-1-(Diphenylphosphanyl)-2,1′-[1-(diphenylphosphanyl)pentan-1,5-diyl]ferroceneC39H36FeP2[α]D = −839 (c 0.22, acetone)Source of chirality: stereoselective synthesisAbsolute configuration: (RpS)

(R,pS)-1-(Diphenylphosphanyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]ferroceneC29H32FeNP[α]D = −404 (c 1.7, CHCl3)Source of chirality: stereoselective synthesisAbsolute configuration: RpS

(R)-1,1′-[1-(Dimethylamino)pentan-1,5-diyl]ferroceneC17H23FeN[α]D = +9.5(c 1.06, CHCl3)Source of chirality: stereoselective synthesisAbsolute configuration: R