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The aldol reaction (aldol addition) is a reaction in organic chemistry that combines two carbonyl compounds (e.g. aldehydes or ketones) to form a new β-hydroxy carbonyl compound. Its simplest form might involve the nucleophilic addition of an enolized ketone to another:
Intramolecular aldol reactions have been widely used in total syntheses of various natural products, especially alkaloids and steroids. An example is the application of an intramolecular aldol reaction in the ring closure step for total synthesis of (+)-Wortmannin by Shigehisa, et al. [5] (Figure 2).
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to give a conjugated enone. The overall reaction equation is as follows (where the Rs can be H)
An aldol may also use the term β-hydroxy aldehyde (or β-hydroxy ketone for a ketol). The term "aldol" may refer to 3-hydroxybutanal. [1] [2] Aldols are the product of a carbon-carbon bond-formation reaction, giving them wide applicability as a precursor for a variety of other compounds.
The Hajos–Parrish–Eder–Sauer–Wiechert and Barbas-List [1] reactions in organic chemistry are a family of proline-catalysed asymmetric aldol reactions.. In the 1970s, two research groups discovered (and published) almost simultaneously their discoveries of two related intramolecular reactions: Zoltan Hajos and David Parrish at Hoffmann-La Roche [2] [3] and Rudolf Wiechert et al at ...
A typical reaction involving two ketones is that between acetophenone as the enol and acetone: [7] Mukaiyama aldol between two ketones. Ketone reactions of this type require higher reaction temperatures. For this work Mukaiyama was inspired by earlier work done by Georg Wittig in 1966 on crossed aldol reactions with lithiated imines.
Completing the cyclooctane ring required 3 more carbon atoms that were supplied by a C2 fragment in an aldol addition and a Grignard C1 fragment (scheme 2).A Mukaiyama aldol addition (magnesium bromide / toluene) took place between aldehyde 7 and ketene silyl acetal 8 with 71% stereoselectivity to alcohol 9 which was protected as the TBS ether 10 (TBSOTf, 2,6-lutidine).
Multiple Michael/aldol reaction (or domino Michael/aldol reaction) is a consecutive series of reactions composed of either Michael addition reactions or aldol reactions. More than two steps of reaction are usually involved. This reaction has been used for synthesis of large macrocyclic or polycyclic ring structures.