A rare case of facial selectivity inversion for Sharpless asymmetric dihydroxylation in a series of structurally homogeneous substrates: synthesis of non-racemic 3-(nitrophenoxy)-propane-1,2-diols

Asymmetric dihydroxylation of mono nitrophenyl allyl ethers leads to the corresponding non-racemic 3-(nitrophenoxy)-propane-1,2-diols 1a–c. As this takes place, regardless of the reagent used (AD-mix-α or AD-mix-β), the configuration of the predominant enantiomer for the para- and meta-nitrosubstituted products is opposite to the configuration of the ortho-nitrophenyl derivative. A correlation between the melting points and vibrational spectra of the racemic and enantiopure diols 1a–c allowed us to establish that all of the chiral substances investigated formed stable racemic compounds in the solid phase.

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(R)-3-(2-Nitrophenoxy)-1,2-propanediolC9H11NO5Ee = 99.2% (ee from HPLC)[α]D20 = −0.5 (c 1, EtOH); [α]43620 = −4.2 (c 1, EtOH)Initial source of chirality: (R)-3-chloro-1,2-propanediolAbsolute configuration: (R)

(R)-3-(3-Nitrophenoxy)-1,2-propanediolC9H11NO5Ee = 99.2% (ee from HPLC)[α]D20 = −15.0 (c 1, EtOH); [α]43620 = −31.1 (c 1, EtOH)Initial source of chirality: (R)-3-chloro-1,2-propanediolAbsolute configuration: (R)

(R)-3-(4-Nitrophenoxy)-1,2-propanediolC9H11NO5Ee >99% (ee from HPLC)[α]D20 = −17.4 (c 1, EtOH); [α]43620 = −37.2 (c 1, EtOH)Initial source of chirality: (R)-3-chloro-1,2-propanediol; AD-mix-αAbsolute configuration: (R)