alkynylated

Alkynylated describes a molecule that has been functionalized by the introduction of an alkynyl group, typically a C≡C unit, into a substrate. The alkynyl moiety can be attached to carbon or heteroatoms and may be terminal or internal, depending on the method and substrates used. Alkynylation provides a versatile handle for further chemical transformation.

Various methods are used to achieve alkynylation. Palladium-catalyzed cross-coupling, such as the Sonogashira reaction, couples terminal alkynes with aryl or vinyl halides to form aryl- or vinyl-alkynyl products. Direct C–H alkynylation uses transition metals or photoredox catalysis to install alkynyl groups at C–H bonds. Electrophilic alkynylation methods employ reagents like ethynylbenziodoxolones to transfer alkynyl groups to electron-rich substrates. Copper- or nickel-catalyzed approaches can also mediate alkynyl transfer from alkynyl sources to nucleophiles or electrophiles.

Alkynylation products are valued for their synthetic versatility and potential for rapid diversification, particularly because the alkyne unit participates in many downstream transformations, including click chemistry with azides and various cycloadditions. Selectivity in alkynylation is influenced by substrate electronics and the choice of catalyst, and common challenges include competing side reactions such as homocoupling of alkynes or sensitivity to air and moisture.

Using alkynylated substrates, chemists assemble complex molecules in medicinal chemistry, natural product synthesis, and materials science. The alkynyl group serves as a reactive handle for further functionalization, enabling iterative building of molecular complexity while preserving a broad range of functional groups.