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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)
α-hydroxy ketones give positive Tollens' and Fehling's test. Some acyloins rearrange with positions swapped under the influence of base in the Lobry–de Bruyn–van Ekenstein transformation; A similar reaction is the so-called Voigt amination [6] where an acyloin reacts with a primary amine and phosphorus pentoxide to an α-keto amine: [7]
Hydroxyacetone can be produced by degradation of various sugars. In foods, it is formed by the Maillard reaction. It reacts further to form other compounds with various aromas. [6] As such it finds some use as a flavoring.
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 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 ...
Alpha-ketoglutarate-dependent hydroxylases are a major class of non-heme iron proteins that catalyse a wide range of reactions. These reactions include hydroxylation reactions, demethylations, ring expansions, ring closures, and desaturations. [1] [2] Functionally, the αKG-dependent hydroxylases are comparable to cytochrome P450 enzymes.
Alpha hydroxy carboxylic acids, or α-hydroxy carboxylic acids (AHAs), are a group of carboxylic acids featuring a hydroxy group located one carbon atom away from the acid group. This structural aspect distinguishes them from beta hydroxy acids , where the functional groups are separated by two carbon atoms. [ 1 ]
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: