Organocatalytic kinetic resolution of a planar-chiral ferrocenecarbaldehyde

The proline-catalyzed aldol reaction of racemic 2-(2′-pyrimidyl)ferrocenecarbaldehyde with acetone in DMSO at room temperature constitutes as the first example of an organocatalytic kinetic resolution of a planar-chiral compound. The selectivity factor of the kinetic resolution is 9.2, and the stereochemical outcome of the process can be easily rationalized by the standard mechanistic model of the proline-catalyzed aldol reaction.

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(pR)-2-(2′-Pyrimidyl)ferrocenecarbaldehydeC15H12FeN2OEe = 78% (HPLC)[α]D20=+26.0 (c 1.1, CHCl3)Source of chirality: organocatalytic kinetic resolutionAbsolute configuration: (pR)

(pS,E)-4-[2-(2′-Pyrimidyl)ferrocenyl]but-3-ene-2-oneC18H16FeN2OEe = 56% (HPLC)[α]D20=+648 (c 0.05, CHCl3)Source of chirality: organocatalytic kinetic resolutionAbsolute configuration: (pS,E)

(R,pS)-4-[2-(2′-Pyrimidyl)ferrocenyl]-4-hydroxy-2-butanoneC18H18FeN2O2Ee = 52% (HPLC)[α]D20=-28.0 (c 0.05, CHCl3)Source of chirality: organocatalytic kinetic resolutionAbsolute configuration: (R,pS)