Combinatorial Chemistry Review

α-Lithioamine synthetic equivalents from dipole-stabilized carbanions: the t-Boc group as an activator for α-lithiation of carbamates

Peter Beak and Won-Koo Lee, Tetrahedron Letters, Vol. 30, 10, pp. 1197-1200, 1989

The t-Boc group activates the α-lithiation of piperidinyl and related carbamates to give lithium reagents which add to electrophiles to provide α-elaborated carbamates. Elaboration of secondary amines by the sequence of addition of an activating group to nitrogen, α-lithiation, electrophilic substitution, and removal of the activating group to give the α-substituted amine has become a useful synthetic strategy in recent years. Use of the formamidine group as the activating function, discovered by Meyers and coworkers, is a notable example. We have sought a dipole-stabilizing group which would be convenient to use and effective with typical secondary amines. In this communication we wish to report that the well-know t-Boc group, which is easily added and removed, can direct α-lithiation.

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