C2-Symmetric nitroxides and their potential as enantioselective oxidants

The synthesis and evaluation of four C2-symmetric nitroxides are presented. The nitroxides were evaluated for their ability to mediate the oxidation of several alcohols and found to have good catalytic activity. One enantioenriched nitroxide was found to kinetically resolve selected secondary alcohols with very modest selectivities.

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2,5-Dimethyl-7-aza-bicyclo[2.2.1]heptane bromideC8H16BrNEe = 90%[α]D23=+17.0 (c 0.705, MeOH)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2S,4R,5S)

(1R,2R,5S,6R)-5-Azido-2,6-dimethylcyclooctanolC10H19N3OEe = 89%[α]D23=+25.6 (c 0.31, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,5S,6R)

(1S,2S,4S,5S)-(+)-2,5-Dimethylcyclohexane-1,4-diolC8H16O2Ee = 90%[α]D23=+29.7 (c 0.51, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,2S,4S,5S)

(1S,2S,4S,5S)-(+)-2,5-Dimethylcyclohexane-1,4-methanesulfonateC10H20O6S2Ee = 90%[α]D23=+29.8 (c 1.025, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,2S,4S,5S)

(1S,2S,4R,5S)-4-Azido-2,5-dimethylcyclohexyl methanesulfonateC9H17N3O3SEe = 90%[α]D23=+27.6 (c 2.30, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,2S,4R,5S)