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As the name suggests, a non-nucleophilic base is an organic base that is a very strong base but at the same time a poor nucleophile. In thermodynamic reaction control an electron donor molecule acts as a nucleophile, in kinetic reaction control the electron donor abstracts a proton (or rather the proton gets harpooned, hence its alternative name harpoon base). For this reason these bases are said to be involved in kinetic deprotonation.
Non-nucleophilic bases include:
The following diagram shows how the hindered base, lithium diisopropylamide, is used to form to deprotonate an ester to give the enolate in the Claisen ester condensation, instead of undergoing a nucleophilic substitution.
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