The Allan–Robinson reaction is the
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
of o-hydroxyaryl
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s with aromatic
anhydride
An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the pa ...
s to form
flavone
Flavone is an organic compound with the formula . A white solid, flavone is a derivative of chromone with a phenyl (Ph) substituent adjacent to the ether group. The compound is of little direct practical importance, but susbstituted derivatives, t ...
s (or
isoflavone Isoflavones are substituted derivatives of isoflavone, a type of naturally occurring isoflavonoids, many of which act as phytoestrogens in mammals. Isoflavones are produced almost exclusively by the members of the bean family, Fabaceae (Leguminosae ...
s).
If
aliphatic
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, or ...
anhydrides are used,
coumarin
Coumarin () or 2''H''-chromen-2-one is an aromatic organic chemical compound with formula . Its molecule can be described as a benzene molecule with two adjacent hydrogen atoms replaced by a lactone-like chain , forming a second six-membered h ...
s can also be formed. (See
Kostanecki acylation
The Kostanecki acylation is a method used in organic synthesis to form chromones or coumarins by acylation of ''O''-hydroxyaryl ketones with aliphatic acid anhydrides, followed by cyclization. If benzoic anhydride (or benzoyl chloride) is used, ...
.)
:
Mechanism
:
The first step is an enolization which is a proton transfer created a hydroxide instead of a carbonyl and an alkene instead of an alkane. The second step is an acylation in which the newly formed bond from the enolization attacks an electrophilic carbon in the anhydride. The third step displays the carboxylate functionality leaving since it is the best leaving group. As a result, the resulting carboxylate attacks an alpha hydrogen to create the enol functionality again in step four. The fifth step shows the nucleophilic hydroxide attacking the carbonyl carbon to create a new six membered heterocyclic ring. The resulting structure undergoes a proton transfer in step 6 to achieve the final product. All six of these steps occur in the reaction flask in the presence of heat.
See also
*
Baker–Venkataraman rearrangement The Baker–Venkataraman rearrangement is the chemical reaction of 2-acetoxyacetophenones with base to form 1,3-diketones.
This rearrangement reaction proceeds via enolate formation followed by acyl transfer. It is named after the scientists Wils ...
*
Kostanecki acylation
The Kostanecki acylation is a method used in organic synthesis to form chromones or coumarins by acylation of ''O''-hydroxyaryl ketones with aliphatic acid anhydrides, followed by cyclization. If benzoic anhydride (or benzoyl chloride) is used, ...
*
Robert Robinson (organic chemist)
Sir Robert Robinson (13 September 1886 – 8 February 1975) was a British organic chemist and Nobel laureate recognised in 1947 for his research on plant dyestuffs (anthocyanins) and alkaloids. In 1947, he also received the Medal of Freedom ...
References
Carbon-carbon bond forming reactions
Heterocycle forming reactions
Name reactions
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