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N,N-Diisopropylethylamine, or Hünig's base, is an organic compound and an amine. It is named after the German chemist Siegfried Hünig. It is used in organic chemistry as a base. It is commonly abbreviated as DIPEA, DIEA, or i-Pr2NEt.

Structure
DIPEA consists of a central nitrogen that is bonded to an ethyl group and two isopropyl groups. A lone pair of electron resides on the nitrogen atom, which can react with electrophiles. However, as the two isopropyl and the ethyl group occupy much of the space surrounding the nitrogen, only small electrophiles such as protons can react with the nitrogen lone pair.

Occurrence and Preparation
DIPEA is synthetically produced and commercially available. It is traditionally prepared by the alkylation of diisopropylamine with diethyl sulfate.

Pure DIPEA exists as a colorless liquid, although commercial samples can be slightly yellow. If necessary, the compound can be purified by distillation from potassium hydroxide or calcium hydride.

Uses and reactions
DIPEA is a hindered base that is commonly employed as an acid or proton scavenger. Thus, like 2,2,6,6-tetramethylpiperidine and triethylamine, DIPEA is a good base but a poor nucleophile, a combination of properties that makes it a useful organic reagent.

Amide coupling
It is commonly used as the hindered base in amide coupling reactions between an acid (that is typically activated, for example, as an acid chloride, as illustrated below) and a nucleophilic amine. As DIPEA is hindered and poorly nucleophilic, it does not compete with the nucleophilic amine in the coupling reaction.



Alkylations
DIPEA was investigated for its use as a selective reagent in the alkylation of secondary amines to tertiary amines by alkyl halides. This is often hampered by an unwanted Menshutkin reaction forming a quaternary ammonium salt but this side-reaction is absent when Hünig's base is present.


 * [[Image:Use of Hunig's base for alkylating secondary amines.png|500px|The use of Hünig's base for alkylating secondary amines]]

Transition metal catalyzed cross-coupling reactions
DIPEA can be used as a base in a number of transition metal catalyzed cross-coupling reactions, such as the Heck coupling and the Sonogashira coupling (as illustrated below).



Swern Oxidation
Although triethylamine is traditionally employed as the hindered base in Swern oxidations, the structurally similar DIPEA could be used instead, as exemplified below.



Examples of DIPEA used as a substrate
DIPEA forms a complex heterocyclic compound called scorpionine by a reaction with disulfur dichloride catalyzed by DABCO in a one-pot synthesis.


 * Sscorpionine_synthesis.png]]

Comparison with triethylamine
DIPEA and triethylamine are structurally very similar, with both compounds considered hindered organic bases. Due to their structural similarity, DIPEA and triethylamine can be used interchangeably in most applications. The nitrogen atom in DIPEA is more shielded than the nitrogen atom in triethylamine. However, triethylamine is a slightly stronger base than DIPEA; pKa of the respective conjugate acids in dimethylsulfoxide are 9.0 and 8.5, respectively.