Remote Protection Prevents Unwanted Cyclizations with 2-Aminopyridines.

The pyridine nitrogen of the 2-aminopyridine group is sufficiently nucleophilic to undergo intramolecular cyclizations, thereby preventing competing Mitsunobu and other substitution reactions from proceeding at a remote site. Double protection of the 2-amino group effectively blocked reaction at the pyridine nitrogen. This is a rare example of the use of a remote protecting group to block another group from reacting.