The Winstein rearrangement involves the equilibration of allylic azides between branched and linear isomers. This study investigates the effect of proximal functionality on the Winstein rearrangement equilibrium. A total of 16 azides with different functional groups neighboring the allylic azide group were synthesized. The selected functional groups represent a range of properties and are divided into three classes: oxygen-based, secondary-amine-based, and tertiary-amine-based. After synthesis, each allylic azide was allowed to equilibrate and then analyzed by <sup>1</sup>H NMR to determine the equilibrium ratio of branched and linear isomers. We observe an electronic effect that strongly correlates with the pKa of the -OR proximal group (oxygen class). We also observe an increase in % branched in the N-H series (secondary-amine class) relative to the N-Bn series (tertiary-amine class), but a lack of solvent effects on the equilibrium position of the rearrangement suggests minimal involvement of an intramolecular hydrogen-bond. Rather, computational studies into the allylic azide system indicate that this shift towards N-H % branched is stereoelectronic in nature.

Effect of proximal functionality on the allylic azide equilibrium

255th National Meeting (2018)

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