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Dibenzylideneacetone or dibenzalacetone, often abbreviated dba, is an organic compound with the formula C 17 H 14 O. It is a pale-yellow solid insoluble in water, but soluble in ethanol. It is a pale-yellow solid insoluble in water, but soluble in ethanol.
This reaction is named after two of its pioneering investigators Rainer Ludwig Claisen and J. Gustav Schmidt, who independently published on this topic in 1880 and 1881. [ 1 ] [ 2 ] [ 3 ] An example is the synthesis of dibenzylideneacetone ((1 E , 4 E )-1,5-diphenylpenta-1,4-dien-3-one).
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base. The reaction produces a β-keto ester or a β-diketone. [1] It is named after Rainer Ludwig Claisen, who first published his work on the reaction in 1887.
Benzylideneacetone can be efficiently prepared by the base-induced condensation of acetone and benzaldehyde: [3]. CH 3 C(O)CH 3 + C 6 H 5 CHO → C 6 H 5 CH=CHC(O)CH 3 + H 2 O. However, the benzylideneacetone formed via this reaction can undergo another Claisen-Schmidt condensation with another molecule of benzaldehyde to form dibenzylideneacetone.
The Johnson–Claisen rearrangement is the reaction of an allylic alcohol with an orthoester to yield a γ,δ-unsaturated ester. [31] Weak acids, such as propionic acid, have been used to catalyze this reaction. This rearrangement often requires high temperatures (100–200 °C) and can take anywhere from 10 to 120 hours to complete. [32]
The reaction is known as the Claisen reaction and was described by Claisen for the first time in 1890. Discovered the thermally induced rearrangement of allyl phenyl ether in 1912. He details its reaction mechanism in his last scientific publication (1925). In his honor, the reaction has been named the Claisen rearrangement.
The reaction between menthone ((2S,5R)-2-isopropyl-5-methylcyclohexanone) and anisaldehyde (4-methoxybenzaldehyde) is complicated due to steric shielding of the ketone group. This obstacle is overcome by using a strong base such as potassium hydroxide and a very polar solvent such as DMSO in the reaction below: [19] A Claisen–Schmidt reaction
The ortho-Claisen rearrangement involves the [3,3] shift of an allyl phenyl ether to an intermediate which quickly tautomerizes to an ortho-substituted phenol. Aromatic Claisen rearrangement When both the ortho positions on the benzene ring are blocked, a second [3,3] rearrangement will occur.