Generating α,β-unsaturated carboxylic acids (cinnamic acid derivatives) in the presence of a weak base from aromatic aldehydes with the anhydrides of aliphatic carboxylic acids is known as the Perkin reaction. An enolate intermediate is made from the anhydride, which undergoes a condensation reaction with benzaldehyde, followed by an intramolecular acyl...

The Pictet-Spengler reaction uses catalytic acid to convert a β-arylethylamine and an aldehyde or ketone to a substituted tetrahydroisoquinoline. First β-arylethylamine attacks the carbonyl carbon, forming a tetrahedral intermediate, which is dehydrated to afford the corresponding Schiff base. Upon protonation, a 6-endo-trig cyclization occurs, disrupting ring aromaticity. Loss of an...

The acid-catalyzed condensation of alkenes with aldehydes is known as the Prins reaction. A protonated aldehyde is attacked by the alkene to afford the most stable β-hydroxyl carbocation that can engage in various reaction pathways dependent on the reaction conditions: (i) Water and a hydrogen atom on the carbon adjacent...

The Reformatsky reaction uses zinc metal and an acid work-up to convert an α-haloester and an aldehyde or ketone to a β-hydroxyester. Zinc metal is first inserted into the carbon-halogen bond of the α-haloester, followed by the formation of an O-zinc enolate, which undergoes an aldol reaction with the carbonyl...

The Reimer-Tiemann reaction uses a dichlorocarbene precursor molecule such as chloroform, an alkali hydroxide, and a protic solvent to convert a phenol to an ortho-formyl phenol. The base first abstracts the hydrogen from chloroform, creating a trichlorocarbanion, which loses a chloride ion to form dichlorocarbene. Phenol is then deprotonated by...

In three distinct steps, the Robinson annulation converts a ketone and an α,β-unsaturated ketone into a substituted cyclohexenone compound. First, the base creates an enolate ion intermediate, which reacts with the α,β-unsaturated ketone in a conjugate 1,4 addition (Michael reaction) to form a 1,5 diketone. An intramolecular aldol reaction occurs...