Rearrangement of chiral 1-bromo-N-nitrobicyclo[2.2.1]heptan-2-imines

The regio- and diastereospecific Wagner-Meerwein-type rearrangements of the potassium cyanide adducts of camphor-derived substituted 1-bromo-N-nitrobicyclo[2.2.1]heptan-2-imines under acidic conditions have been investigated. The selective formation of bromonorbornene derivatives has been demonstrated in the case of rearrangements involving intermediate α-bromocarbocations containing vicinal hydrogen atoms. In all other cases, hydrolysis of the intermediates resulted in the formation of a carbonyl group. The simplicity of this transformation opens up a novel and straightforward synthetic pathway to enantiopure derivatives of bridgehead-substituted norbornane carboxamides in just three steps, starting from 1-bromonorbornanones.

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(1R,4R)-1-Bromo-3,3,4-trimethylbicyclo[2.2.1]heptan-2-one oximeC10H16BrNOde = 100%[α]D20=-38.0 (c 0.88, CHCl3)Source of chirality: (R)-(+)-camphorAbsolute configuration: (1R,4R)

(1R,4R)-1-Bromo-3,3-dimethylbicyclo[2.2.1]heptan-2-one oximeC9H14BrNOde = 100%[α]D20=-59.6 (c 0.87, CHCl3)Source of chirality: (R)-(+)-camphorAbsolute configuration: (1R,4R)

(1R,4S)-1-Bromo-7,7-dimethylbicyclo[2.2.1]heptan-2-one oximeC9H14BrNOde = 100%[α]D20=-49.3 (c 0.85, CHCl3)Source of chirality: (S)-(-)-camphorAbsolute configuration: (1R,4S)

(1R,4R)-1-Bromo-3,3,4-trimethyl-N-nitrobicyclo[2.2.1]heptan-2-imineC10H18BrN2O2de = 100%[α]D20=-65.3 (c 0.86, CHCl3)Source of chirality: (R)-(+)-camphorAbsolute configuration: (1R,4R)

(1R,4R)-1-Bromo-3,3-dimethyl-N-nitrobicyclo[2.2.1]heptan-2-imineC9H13BrN2O2de = 100%[α]D20=-73.2 (c 0.93, CHCl3)Source of chirality: (R)-(+)-camphorAbsolute configuration: (1R,4R)

(1R,4S)-1-Bromo-7,7-dimethyl-N-nitrobicyclo[2.2.1]heptan-2-imineC9H13BrN2O2de = 100%[α]D20=-41.25 (c 0.91, CHCl3)Source of chirality: (S)-(-)-camphorAbsolute configuration: (1R,4S)

(1R,4R)-2-Bromo-4,7,7-trimethylbicyclo[2.2.1]hept-2-ene-1-carboxamideC11H17BrNOde = 100%[α]D20=+73.35 (c 0.85, CHCl3)Source of chirality: (R)-(+)-camphorAbsolute configuration: (1R,4R)

(1R,4R)-2-Bromo-7,7-dimethylbicyclo[2.2.1]hept-2-ene-1-carboxamideC10H14BrNOde = 100%[α]D20=+75.65 (c 0.81, CHCl3)Source of chirality: (R)-(+)-camphorAbsolute configuration: (1R,4R)

(1S,4S)-3,3-Dimethyl-2-oxobicyclo[2.2.1]heptane-1-carboxamideC10H15BrNO2de = 100%[α]D20=-52.5 (c 1.30, CHCl3)Source of chirality: (S)-(-)-camphorAbsolute configuration: (1S,4S)