Enal
An enone, also called an α,β-unsaturated carbonyl, is a type of organic compound consisting of an alkene conjugated to a ketone. The simplest enone is methyl vinyl ketone (butenone) or CH2=CHCOCH3. An enal is the corresponding α,β-unsaturated aldehyde, an example being acrolein (CH2=CHCHO).
Enones are typically produced using an Aldol condensation or Knoevenagel condensation. Some commercially significant enones are produced by condensations of acetone, e.g. mesityl oxide and isophorone.
In the Meyer–Schuster rearrangement the starting compound is a propargyl alcohol. Cyclic enones can be prepared via the Pauson–Khand reaction.
Enones undergo many kinds of reactions.
They are electrophilic at both the carbonyl carbon as well as the β-carbon. Depending on conditions, either site is attacked by nucleophiles. Addition to the alkene is called conjugate additions. Michael additions are examples.
Enones are often good dienophiles in Diels-Alder reactions. They are activated by Lewis acids, which bind to the carbonyl oxygen.
Enones are readily reduced. They can undergo both reduction of the carbonyl and of the alkene (conjugate reduction), as well as both.
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