Ketone-alkenes => conjugated ketones

Experiments show that both alkenes and ketones undergo acid-catalyzed reactions. Alkene reactions usually require use of a very strong acid, H2SO4 or HX, while ketone reactions occur under milder conditions. This suggests that ketones are stronger bases, and that their conjugate acids enjoy special stabilization. 

Similar reactions have been carried out on acetylene. Aldehydes add to alkynes in the presence of a rhodium catalyst to give conjugated ketones. In a cyclic version of the addition of aldehydes, 4-pentenal was converted to cyclopen-tanone with a rhodium-complex catalyst. In the presence of a palladium catalyst, a tosylamide group added to an alkene unit to generate A-tosylpyrrolidine derivatives. ... 

This method provides a convenient synthesis of alkenes with the double bond in a relatively unstable position. Thus reduction of the p-toluenesulfonylhydrazones of a,(3-unsaturated aryl ketones and conjugated dienones gives rise to nonconjugated olefins. Unsaturated ketones with endocyclic double bonds produce olefins with double bonds in the exocyclic position. The reduction of p-toluenesulfonylhydrazones of conjugated alkynones furnishes a simple synthesis of 1,3-disubstituted allenes. ... 

This section contains alkylations of ketones and protected ketones, ketone transpositions and annulations, ring expansions and ring openings and dimerizations. Conjugate reductions and Michael alkylations of enone are listed in Section 74 (Alkyls from Alkenes). 

In total, over the past six years, the chelating P,N-ligands have shown considerable promise in a variety of enantioselective processes, including transfer-hydrogenation and hydrosilylation of ketones, hydroboration of alkenes, conjugate addition to enones and Lewis-acid catalysed Diels-Alder reactions, in addition to those described above.128,341 It is anticipated that this list will continue to grow, and... 

In principle, the acylation of aliphatic compounds is analogous with the Friedel-Crafts acylation of aromatics in the sense that a hydrogen of the reacting alkanes, alkenes, or alkynes is replaced by an acyl group to yield ketones, unsaturated ketones, or conjugated acetylenic ketones, respectively. As discussed subsequently, however, the reactions are more complex. The acylation of aliphatics is an important but less frequently used and studied process.11-13... 

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 ... 

Sometimes, an alkene conjugated with a ketone is introduced during a Swern oxidation.172a 232 This can be explained by an a-chlorination followed by elimination of HC1. 

In rare cases, ketones obtained by the oxidation of alcohols with TPAP suffer an in situ over-oxidation, resulting in the introduction of an alkene conjugated with the ketone.106 For example, this happens when thermodynamics are greatly favored by aromatization. 

The Cp2TiCl/H20 combination can also be used for the chemoselective reduction of aromatic ketones. The reaction discriminates between ketones and alkenes, between ketones and esters and, remarkably, between conjugated and non-conjugated ketones [80]. There is strong evidence that this reduction proceeds via ketyl-type radicals, which are finally reduced by H-atom transfer from 42 [81]. Under dry conditions, titanium-promoted ketyl radicals from aromatic ketones can be used for intermolecular and intramolecular cross-coupling of ketones [82], Thus, depending on whether water is added or not, complementary and versatile synthetic procedure protocols are available. 

Compound A is a cyclic, nonconjugated keto alkene whose carbonyl infrared absorption should occur at 1715 cm-. Compound B is an a,B-unsaturated, cyclic ketone additional conjugation with the phenyl ring should lower its IR absorption below 1685 cm-1. Because the actual IR absorption occurs at 1670 cm-1, B is the correct structure. 

Another important asymmetric epoxidation of a conjugated systems is the reaction of alkenes with polyleucine, DBU and urea H2O2, giving an epoxy-carbonyl compound with good enantioselectivity. The hydroperoxide anion epoxidation of conjugated carbonyl compounds with a polyamino acid, such as poly-L-alanine or poly-L-leucine is known as the Julia—Colonna epoxidation Epoxidation of conjugated ketones to give nonracemic epoxy-ketones was done with aq. NaOCl and a Cinchona alkaloid derivative as catalyst. A triphasic phase-transfer catalysis protocol has also been developed. p-Peptides have been used as catalysts in this reaction. ... 

A variant of this reaction couples halides with alkenes. ot-Bromomethyl esters react with conjugated ketones and DABCO to give a coupling product, 34. ° A similar DBU-induced reaction was reported using ot-bromomethyl esters and conjugated nitro compounds. 

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