Treatment of homoallylic N-tosyl amines or allylic N-tosyl hydroxylamines with 1.5 equiv of a malonoyl peroxide provides a stereoselective method to access functionalized pyrrolidines and isoxazolidines. This metal free alkene oxyamination proceeds in 50-85% yield and up to 13:1 trans-selectivity. In addition, the relative stereochemistry of the oxygen and nitrogen substituents can be inverted through an oxidation/reduction sequence or inverting the stereochemistry of the starting alkene. Mechanistic investigations show a higher reactivity for hydroxyl nucleophiles over sulfonamide nucleophiles revealing a preference for dioxygenation over oxyamination.
Malonoyl peroxide 6 is an effective reagent for the syn- or anti-oxyamination of alkenes. Reaction
of 6 and an alkene in the presence of O-tert-butyl-N-tosylcarbamate (R3 = CO2
t
Bu) leads to
the anti-oxyaminated product in up to 99% yield.
Use of O-methyl-N-tosyl carbamate
(R3 = CO2Me) as the nitrogen nucleophile followed
by treatment of the product with trifluoroacetic acid leads to the syn-oxyaminated product in up to 77% yield. Mechanisms consistent
with the observed selectivities are proposed.
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