Diketone formation

Scheme 20 Selectivity of unsymmetrical 1,2-diketone formation from unsymmetrical diesters of 1,n-diols.

The 1,5-diketone formation by the Michael addition of allylsilane (48) to a, -unsaturated ketones was applied to the synthesis of (+)-nootkatone. Reaction of the keto group of keto aldehyde (58) with allyl Orignard reagent and dehydration gave the diene aldehyde (59). The selective oxidation of the terminal double bond afforded the 1,5-dica nyl compound (60), which is not stable and converted directly to pyridines and phenols (Scheme 18). ... 

Grignard reagents have been used directly in mono-and diketone formation. More recently, it has been found that a catalytic quantity of cuprous chloride greatly increases the yields." An example is the formation of hexamethylacetone in 70-80% yield from t-butylmagnesium chloride and trimethylacetyl chloride. Diketones have... 

What happens when p-hydrogcn elimination in the ruthenacyclic intermediate 45 is preduded, as in the case when vinyl ketones are the alkene partners (Equation 1.55) Given the extraordinary ability of Ru to interconvert easily among numerous oxidation states, one can imagine that the Ru can activate the double bond towards additions. For example, in the presence of water, protonation at the carbon (5 to Ru in the ruthenacyclopentene followed by nucleophilic addition of hydroxide can lead to 1,5-diketone formation. Indeed, terminal alkynes undergo smooth three-component coupling to form 1,5-diketones as shown in Equation 1.56 [52]. 

Omura, F. (2008). Targeting of mitochondrial Saccharomyces cerevisiae IlvSp to the cytosol and its effect on vicinal diketone formation in brewing. Applied Microbiology and Biotechnology, 78, 503-513. 

G. DIKETONE FORMATION FROM PALLADIUM-PROMOTED DOUBLE CARBONYLATION... 

Diaryl-a-diketones were obtained in the carbonylation of diaryliodonium salts catalyzed by Pd(OAc)2 in the presence of zincJ In addition to diketones, formation of diaryl ketones, biaryls, and aryl iodides was also found. A synthetic method to yield a-diketones has been developed by carbonylative coupling between diorganozincs and acid halides promoted by palladium complexes (Eq. 26). A diacylpalladium intermediate was proposed in the course of formation of a-diketone. 

Merck chemlsts reported the structures of several by-products formed in transformations of EGEj. Hydrogenation of PGEi with 10 Pd/C in ethyl acetate gave, in addition to the expected 15,l4-dihydro-PGEi (53), about 15 of the diketone Formation of implies that double... 

Ott, A., Germond, J.E., and Chaintreau, A. (2000) Vicinal diketone formation in yogurt 13C precursors and effect of branched-chain amino acids. J Agric Food Chem 48, 724-731. 

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