Rearrangements – Which Group Migrates?

The outcome of diazotization and semipinacol rearrangement of the amino-alcohol depends entirely on the diastereoisomer you start with.

There are four diastereoisomers each one with the t-butyl group equatorial, which locks the cyclohexane conformation. In all of these reactions, the OH group provides the electronic ‘push’ and the group which is anti–periplanar to the leaving group (–N₂⁺) migrates.

^{Click the four diastereoisomers below to view each 3D animation respectively}

Diastereoisomer 1