Non-nucleophilic Bases
A variety of amines and nitrogen heterocycles are useful bases of moderate strength (pKa of conjugate acid around 10-13)
- N,N-Diisopropylethylamine, or DIPEA (also called Hünig's Base)
- 1,8-Diazabicycloundec-7-ene, or DBU—a favorite for the E2 elimination reaction.
- 2,6-Di-tert-butylpyridine
Non-nucleophilic bases of high strength are usually anions. For these species the pKa's of the conjugate acid is around 35-40.
- Lithium diisopropylamide, or LDA
- Silicon-based amides, such as sodium and potassium bis(trimethylsilyl)amide (NaHMDS and KHMDS respectively)
- Lithium tetramethylpiperidide, or LiTMP (harpoon base).
Other strong non-nucleophilic bases are sodium hydride and potassium hydride. These compounds are dense, salt-like materials that are insoluble and operate by surface reactions.
Some reagents are of high basicity (pKa of conjugate acid around 17) but of modest but not negligible nucleophilicity. Examples include sodium tert-butoxide and potassium tert-butoxide.
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