Dynamic Kinetic Resolution of Allylic Azides via Asymmetric Dihydroxylation

The
catalytic enantioselective preparation of densely functionalized
amines is a fundamental synthetic challenge. To address this challenge,
we report for the first time that the Winstein rearrangement can be
enlisted as the racemization pathway in a dynamic kinetic resolution
of allylic azides. Alkene functionalization by Sharpless dihydroxylation
affords tertiary azides in excellent enantioselectivity (up to 99:1
er). This approach establishes the chirality of the tertiary azide,
obviates the need to directly forge either a congested C–N
or C–C bond at the new nitrogenous stereocenter, and establishes
additional functionality. Several examples demonstrate further elaboration
of this functionality.