The principal reaction of interest involves the addition of the
acetylene () to a
ketone () or
aldehyde (): : The reaction proceeds with retention of the
triple bond. For aldehydes and unsymmetrical ketones, the product is
chiral, hence there is interest in asymmetric variants. These reactions invariably involve metal-
acetylide intermediates. This reaction was discovered by chemist
John Ulric Nef in 1899 while experimenting with reactions of elemental
sodium,
phenylacetylene, and
acetophenone. For this reason, the reaction is sometimes referred to as
Nef synthesis. Sometimes this reaction is erroneously called the Nef reaction, a name more often used to describe a different reaction (see
Nef reaction).
Walter Reppe coined the term ethynylation during his work with acetylene and carbonyl compounds. : Common solvents for the reaction are
ethers,
acetals,
dimethylformamide,
Modifications Several modifications of alkynylation reactions are known: • In the
Arens–van Dorp synthesis the compound
ethoxyacetylene is converted to a
Grignard reagent and reacted with a
ketone, the reaction product is a
propargyl alcohol. • In the
Isler modification of the Arens–Van Dorp Synthesis, ethoxyacetylene is replaced by
β-chlorovinyl ethyl ether, and the lithium acetylide is generated in situ using
lithium amide. ==Uses==