Diketones specificity

A solution of bismuth trioxide in hot glacial acetic acid provides a specific method for the oxidation of acyloins. " The reaction rate is dependent on the steric accessibility of the ketol system. A 2,3-ketol requires less than one hour for completion but an 11,12-ketol is not yet fully oxidized in thirty hours." The reaction is highly selective as a-keto acids, hydrazines and phenols are not oxidized. In a direct comparison with cupric acetate, this procedure is somewhat superior for the preparation of a 2,3-diketone from a 2-keto-3-hydroxy steroid. ... 

In addition to the glycol, a compound, Cj H Oj, was formed, which Semmler and Hoffman regard as a keto aldehyde, or a diketone, of specific gravity 1-055. 

This is a l,4 diketone and disconnection of the central bond separates the two rings. We require a specific enol equivalent lor (4) - they used activated ketone (6) - and a reagent for unnatural synthon (5) -they used a-chloroketone (7). 

APG, p-azidophcnyl glyoxal, is a heterobifunctional crosslinker containing an arginine-specific diketone group on one end and a photosensitive phenyl azide group on the other end (Thermo... 

The reduction of diketones is very complex. They can be partially reduced to ketols (hydroxy ketones) or ketones, or completely reduced to hydrocarbons. Depending on the mutual distance of the two carbonyl groups and reagents used, carbon-carbon bond cleavage may occur and may be followed by recyclizations or rearrangements. Some reactions may result in the formation of alkenes. Quinones react in their own specific way. 

Fig. 6 Enzymatic splitting of the oxidised polymer backbone proceeds by two different enzymes depending on the target moiety in the oxidised polymer backbone. Above, the [1-OH-ketone can be opened by an aldolase activity (apoenzyme of PVADH). Below, the diketone element is cleaved by a specific [l-diketone hydrolase (BDH). A non-enzymatic mechanism is also possible...

Although cedranoid sesquiterpenes have earlier been synthesized, a renewed interest in alternative methods for elaborating these frameworks has arisen. The stereo-specific approach to (x-cedrene and a-patchoulene skeletons designed by Deslong-champs and summarized in Scheme XLIII is a case in point Beginning with the Stork-Clarke intermediate 559, the tetracyclic cyclopropyl diketone 560 was elaborated via a series of standard transformations. Treatment of 560 with three equivalents of sodium methoxide in methanol at room temperature for 20 min... 

TA NaBr-MRNi has been found to be an effective catalyst for enantio-differentiating hydrogenations of ketones which have a general structure of R—CO—CH2—X—O— as shown in Table XVII (52c) and methyl ketones as shown in Table XXVI (52d). Among all, /i-diketones and /i-ketoesters are the most favorable substrate for this catalyst. Specific rotations [a] 0 of (R, R )-diols produced from /3-diketones by hydrogenation with this catalyst are summarized in Table XXVII (44). 

Under this section are considered lanthanide complexes of /3-diketones and their adducts, but work specifically in the area of lanthanide shift reagents is dealt with in Section 39.2.9. Of course, the majority of lanthanide shift reagents are lanthanide /3-diketonates, and when they function as shift reagents they do so by forming adducts in solution. Furthermore, interest in shift reagents has directly stimulated a considerable amount of fundamental research on lanthanide /3-diketonates and their adducts. Much of this fundamental work was, therefore, carried out in the early 1970s. AH this means that the division between this section and Section 39.2.9 is not entirely clear cut. 

One of the most general pyrrole syntheses is the cyclizative condensation of 1,4-dicarbonyl compounds with ammonia, a primary amine or related compound. The mechanistic pattern involves formation of carbinolamine and imine intermediates followed by aromatization. This method is sometimes referred to as the Paal-Knorr pyrrole synthesis (equation 65) (B-77MI30601). Once the dicarbonyl compound is available, the cyclization normally proceeds in good yield, so ease of access to the diketone is of major importance in determining the applicability of this method to specific pyrroles. Pyrrole formation usually takes place on heating the diketone in a solvent such as benzene or toluene with a catalytic amount of acid. An alternative method involves heating the dicarbonyl compound and an amine salt... 

Some articles review the coordination chemistry of /3-diketones1529,1530 and, specifically, isomerism1531 and Lewis acid behaviour of the complexes.1532 Amongst the carbon-bonded /3-diketone complexes, those of nickel(II) have not been reported.1533... 

Some papers deal with specific aspects of the Ni(/3-diketonate)2 chemistry, as, for example, mass spectra,1587,1588 CD spectra of adducts with amino acids and amino alcohols,1589,1590 and photochemical reduction.1591... 

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