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Although examples of enantioselective α-ketol rearrangements starting from achiral α-hydroxy ketones are fairly limited, a number of examples of 1,2-asymmetric induction (due to stereoelectronic factors) have been observed. In one example of an enantioselective process, use of nickel(II) diacetoacetonate and pybox provided 4 in 34% ee. [11] (4)
The name acyloin is derived from the fact that they are formally derived from reductive coupling of carboxylic acyl groups (−C(=O)OH). [1] They are one of the two main classes of hydroxy ketones , distinguished by the position of the hydroxy group relative to the ketone; in this form, the hydroxy is on the alpha carbon , explaining the ...
Alpha-hydroxy ketones are also called acyloins. [1] They are commonly formed by condensation or reductive coupling of two carbonyl (C=O) compounds or oxidation of ketones. The simplest such compound is hydroxyacetone. If the alcohol is primary, alpha-hydroxy ketones give a positive Fehling's test. Beta-hydroxy ketones are a type of aldol.
The net reaction between an aldehyde (or an alpha-hydroxy-ketone) and the copper(II) ions in Benedict's solution may be written as: RCHO + 2 Cu 2+ + 5 OH − → RCOO − + Cu 2 O + 3 H 2 O. The hydroxide ions in the equation forms when sodium carbonate dissolves in water. With the citrate included, the reaction becomes:
The following examples represent only a small portion of syntheses that highlight the use of the Rubottom oxidation to install an important α-hydroxy functionality. Some of the major features of the following syntheses include the use of buffered conditions to protect sensitive substrates and the diastereoselective installation of the α ...
It is an α-hydroxyketone, also called a ketol, and is the simplest hydroxy ketone structure. It is a colorless, distillable liquid. It is a colorless, distillable liquid. Preparation
The name combines the suffix 'ol' from the alcohol and the prefix depending on the carbonyl group, either 'ald' for an aldehyde, or 'ket' for a ketone, in which case it referred to as a 'ketol'. 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]
Keto–enol tautomerism refers to a chemical equilibrium between a "keto" form (a carbonyl, named for the common ketone case) and an enol. The interconversion of the two forms involves the transfer of an alpha hydrogen atom and the reorganisation of bonding electrons. The keto and enol forms are tautomers of each other. [2]