In organic chemistry, an ynone is an organic compound containing a ketone () functional group and a triple bond. The simplest ynone is butynone.
Many ynones are α,β-ynones, where the carbonyl and alkyne groups are one bond apart, allowing them to form a conjugated system. Capillin is a natural example of a doubly conjugated ynone.
Non-conjugated ynones have additional sp3 carbon atoms between the carbonyl and alkyne groups which prevent conjugation.
Synthesis of α,β-ynones One method for synthesizing ynones is the acyl substitution reaction of an alkynyldimethylaluminum with an acyl chloride. An alkynyldimethylaluminum compound is the reaction product of trimethylaluminum and a terminal alkyne.
An alternative is the direct coupling of an acyl chloride with a terminal alkyne, using a copper-based nanocatalyst:
Other methods utilize an oxidative cleavage of an aldehyde, followed by reaction with a hypervalent alkynyl iodide, using a gold catalyst.
An alternative but longer synthetic method involves the reaction of an alkynyllithium compound with an aldehyde. The reaction produces a secondary alcohol that then can be oxidized via the Swern oxidation.
Synthesis of β,γ- and γ,δ-ynones Terminal alkynes add across α,β-unsaturated ketones in the presence of palladium catalysts. The reaction affords γ,δ-ynones. Terminal alkynes add across epoxides to given yneols, which can be oxidized to give β,γ-ynones.
Further reading Bis-ynones can undergo an intramolecular cycloaddition to form furan derivatives.
See also Diketone
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