Unsaturated aldehydes ketones

Stabilized anions exhibit a pronounced tendency to undergo conjugate addition to a p unsaturated carbonyl compounds This reaction called the Michael reaction has been described for anions derived from p diketones m Section 18 13 The enolates of ethyl acetoacetate and diethyl malonate also undergo Michael addition to the p carbon atom of a p unsaturated aldehydes ketones and esters For example... 

Recently, the Michael addition of the optically active Q ,y-disubstituted tetronic acids 146c,e with a variety of Q ,/3-unsaturated aldehydes, ketones, esters, and nitriles was studied (Scheme 53) (99H1321). 

When the Mannich base contains an amino group P to a carbonyl (and it usually does), ammonia is easily eliminated. This is a route to a,P-unsaturated aldehydes, ketones, esters, and so on ... 

Several Clostridia including Cl. tyrobutyricum. Cl. thermoaceticum, and Cl. kluyveri are able to reduce the double bond of a,p-unsaturated aldehydes, ketones, and coenzyme A thioesters (Rohdish et al. 2001), and are noted in Chapter 3, Part 3. 

Scheme 32 Unsaturated aldehydes, ketones and esters in the hydroformylation/Mukayama aldol reaction...

The intermediate Michael adducts have been isolated from the reaction of a-chloro-a-nitroalkanes with a, 3-unsaturated aldehydes, ketones, nitriles and esters... 

Another important reaction in synthetic chemistry leading to C-C bond formation is the Michael addition. The reaction typically involves a conjugate or nucleophilic 1,4-addition of carbanions to a,/l-unsaturated aldehydes, ketones, esters, nitriles, or sulfones 157) (Scheme 21). A base is used to form the carbanion by abstracting a proton from an activated methylene precursor (donor), which attacks the alkene (acceptor). Strong bases are usually used in this reaction, leading to the formation of byproducts arising from side reactions such as condensations, dimerizations, or rearrangements. 

The CM of olefins bearing electron-withdrawing functionalities, such as a,/ -unsaturated aldehydes, ketones, amides, and esters, allows for the direct installment of olefin functionality, which can either be retained or utilized as a synthetic handle for further elaboration. The poor nucleophilicity of electron-deficient olefins makes them challenging substrates for olefin CM. As a result, these substrates must generally be paired with more electron-rich crosspartners to proceed. In one of the initial reports in this area, Crowe and Goldberg found that acrylonitrile could participate in CM reactions with various terminal olefins using catalyst 1 (Equation (2))." Acrylonitrile was found not to be active in secondary metathesis isomerization, and no homodimer formation was observed, making it a type III olefin. In addition, as mentioned in Section 11.06.3.2, this reaction represents one of the few examples of Z-selectivity in CM. Subsequent to this report, ruthenium complexes 6 and 7a were also observed to function as competent catalysts for acrylonitrile... 

Precursor y-halogeno alcohols are frequently prepared by the classic sequence of addition of hydrogen halide to a,/3-unsaturated aldehydes, ketones, acids or esters, followed by Grignard reaction or hydride reduction. Recently a novel and general synthesis of 3-methoxyoxetanes from 3-phenylseleno-2-propenal was reported. This method comprises a sequence of Grignard addition to the aldehyde function, treatment with two equivalents of MCPBA, and then reaction with methanolic sodium hydroxide (equation 78) (80JOC4063). 

In a similar manner, carbonyl carbons in a, /f-unsaturated aldehydes, ketones and carboxylic acids are shielded by about 10 ppm when compared with those of corresponding saturated carbonyl compounds [73] ... 

There are many addition reactions of a,(3-unsaturated aldehydes, ketones, and related compounds that are the same as the carbonyl addition reactions described previously. Others are quite different and result in addition to the alkene double bond. Organometallic compounds are examples of nucleophilic reagents that can add to either the alkene or the carbonyl bonds of conjugated ketones (see Section 14-12D). Hydrogen cyanide behaves likewise and adds to the carbon-carbon double bond of 3-butene-2-one, but to the carbonyl group of 2-butenal ... 

Unsaturated aldehydes, ketones and esters undergo hydroformylation of die double bond without reaction at the carbonyl group. For example, dienes yield aldehydes in a stepwise fashion (vide supra) however, a,(3-unsaturated aldehydes and ketones undergo rapid hydrogenation to the saturated aldehyde... 

The majority of the known cuticular lipid constituents that function in chemical communication processes are hydrocarbons (Howard and Blomquist, 1982 Blomquist and Dillwith, 1985 Howard, 1993 Nelson and Blomquist, 1995). Most oxygenated lipids that function as pheromones are not part of the surface lipids but are secretory products of specialized glands (Tamaki, 1985 Am et al, 1986 Morgan and Mandava, 1988). Many of the compounds in pheromones are short-chain unsaturated aldehydes, ketones and acetate esters of short-chain (C10-C14) unsaturated alcohols. Those short-chain lipids (biological activity have been reviewed elsewhere (Blomquist and Dillwith, 1985 Tamaki, 1985 Lockey, 1988 Blomquist et al., 1993 Jurenka and Roelofs, 1993 Howard, 1993). 

Stork has used the addition of a,/ -unsaturated aldehydes, ketones, esters, and nitriles to enamines prepared from ketones and pyrrolidine, piperidine, or morpholine for the synthesis of a-substituted carbonyl compounds264 266 (Scheme 9). 

The presence of a carbon—carbon double bond conjugated to a carbonyl group (an a,/3-unsaturated aldehyde, ketone, and so on) in the target compound suggests that an aldol condensation be employed ... 

Diisobutylaluminum benzenetellurolate, prepared from diphenyl ditellurium and diisobutylaluminum hydride, adds in a 1,4-fashion to a,/i-unsaturated aldehydes, ketones, and carboxylic acid esters to give as intermediates /i-phenyltelluro-substituted aluminum enolates that can be hydrolyzed to the carbonyl compounds or reacted with aldehydes to produce aldol adducts2. 

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