Pentanedionates

Nonanedione, another 1,3-difunctional target molecule, may be obtained from the reaction of hexanoyl chloride with acetonide anion (disconnection 1). The 2,4-dioxo substitution pattern, however, is already present in inexpensive, symmetrical acetylacetone (2,4-pentanedione). Disconnection 2 would therefore offer a tempting alternative. A problem arises because of the acidity of protons at C-3 of acetylacetone. This, however, would probably not be a serious obstacle if one produces the dianion with strong base, since the strongly basic terminal carbanion would be a much more reactive nucleophile than the central one (K.G. Hampton, 1973 see p. 9f.). 

Ethyl-cf-chloroacetoacetate gives 5-carbethoxy-4-methyl-2-thiazole thiol (387), while 3-chloro-2,4-pentanedione affords the 2-mercapto-4-methyl-5-thiazolylmethylketone in good yield (74%) (387). 

Both of these features are apparent m the structure of the enol of 2 4 pentanedione shown in Figure 18 2... 

Learning By Model mg contains molecu lar models of the enolates of acetone and 2 4 pentanedione Compare the two with respect to the dis tribution of negative charge... 

By far the most popular commercial ketone peroxide is methyl ethyl ketone peroxide [1338-23-4]. Smaller quantities of ketone peroxides such as methyl isobutyl ketone peroxide [28056-59-9] cyclohexanone peroxide [12262-58-7] and 2,4-pentanedione peroxide [37187-22-7] are used commercially (47). 

Ketones with labile hydrogen atoms undergo enol acetylation on reaction with ketene. Strong acid catalysis is required. If acetone is used, isoptopenyl acetate [108-22-5] (10) is formed (82—85). Isopropenyl acetate is the starting material for the production of 2,4-pentanedione (acetylacetone) [123-54-6] (11). 

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