Unsaturates ketones and aldehydes

Ailyl enol carbonates derived from ketones and aldehydes undergo Pd-cat-alyzed decarboxylation-elimination, and are used for the preparation of a, /3-unsaturated ketones and aldehydes. The reaction is regiospecific. The regio-isomenc enol carbonates 724 and 726, prepared from 723, are converted into two isomeric enones, 725 and 727. selectively. The saturated aldehyde 728 can be converted into the a,/3-unsaturated aldehyde 730 via the enol carbonate 729[459]. 

It has long been known that a, / -unsaturated sulfones resemble a, /i-unsaturated ketones and aldehydes in undergoing addition reactions with nucleophilic reagents43. These reactions are initiated by nucleophilic attack at the carbon to the sulfone group ... 

Reduction of aryl diazonium ions by Ti(III) in the presence of a,(3-unsaturated ketones and aldehydes leads to (3-arylation and formation of the saturated ketone or aldehyde. The early steps in this reaction parallel the copper-catalyzed reaction. However, rather than being oxidized, the radical formed by the addition step is reduced by Ti(III).116... 

The addition of allyl alcohol to alkynes to form y,8-unsaturated ketones and aldehydes (Eq. 3.46) in aqueous media was developed by both Trost and Dixneuf.182... 

In contrast to kinetic models reported previously in the literature (18,19) where MO was assumed to adsorb at a single site, our preliminary data based on DRIFT results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups being coordinated to the catalyst. This diadsorption mode for a-p unsaturated ketones and aldehydes on palladium have been previously suggested based on quantum chemical predictions (20). A two parameter empirical model (equation 4) where - rA refers to the rate of hydrogenation of MO, CA and PH refer to the concentration of MO and the hydrogen partial pressure respectively was developed. This rate expression will be incorporated in our rate-based three-phase non-equilibrium model to predict the yield and selectivity for the production of MIBK from acetone via CD. 

Mechanisms, exemplified by alcohol as donor (493, 496), usually invoke coordination of the substrate (olefins, saturated and unsaturated ketones, and aldehydes), then coordination of the alcohol and formation of a metal alkoxide, followed by /8-hydrogen transfer from the alkoxide and release of product via protonolysis ... 

One of the most active and selective catalysts in this kind of reaction is undoubtedly Ir/support, as recently demonstrated by Jacobs and coworkers [276], Therefore, by combining the carbonyl affinity of metallic iridium with the promotion effect of the H-fl zeolite, which is a strong Bronsted acid, one can reduce a large variety of unsaturated ketones and aldehydes to allylic alcohols with high conversions, selectivities, and diasteieoselectivities. 

A modified version of the Brown-Negishi reaction using B-alkylcatechol-boranes was reported (Scheme 32). This novel method is based on a simple one-pot procedure involving the hydroboration of various substituted alkenes with catecholborane, followed by treatment with catalytic amount of oxygen/DMPU/water and a radical trap. Efficient radical additions to a,ft-unsaturated ketones and aldehydes have been reported. Primary alkyl radicals are efficiently generated by this procedure and the reaction has been applied to a 300 mmol scale synthesis of the y-side chain of (-)-perturasinic... 

These a,/l-unsaturated ketones and aldehydes are used as reactants in Michael additions (Section 1.10) and Robinson annulations (Section 2.1.4), as well as in a number of other reactions that we will encounter later. Entries 8 and 9 in Scheme 2.11 illustrate Michael reactions carried out by in situ generation of a,/ -unsaturated carbonyl compounds from Mannich bases. 

In 1978, Saegusa and coworkers discovered that silyl enol ethers can be converted into a,b-unsaturated ketones and aldehydes by Pd" [193]. In the presence of 0.5 equivalents of BQ, substoichiometric Pd(OAc)2 (0.5 equiv) effects nearly quantitative conversion of the substrate into product in acetonitrile (Eq. 51). Attempts to lower the catalyst loading further results in longer reaction times as well as increased yields of saturated carbonyl by-product. 

Conjugate reduction of enones. a./ -Unsaturated ketones and aldehydes undergo 1,4-reduction in generally high yield with I equivalent of lithium aluminum hydride in the presence of 10 mole % of Cul and 1 equivalent of HMPT at -78°. The active agent presumably is LiHCuI. Cul can be replaced by mesitylcoppcr and copper(I) t-butoxide. 

Unsaturated ketones and aldehydes react with acceptor-substituted... 

Cho, C. S. Motoffisa, S.-I. Ohe, K. Uemura, S. Shim, S. C. A new catalytic activity of SbCl3 in Pd(0)-catalyzed conjugate addition of aromatics to a,/3-unsaturated ketones and aldehydes with NaBPh and arylboronic adds. 

In order to obtain sufficient adhesion of printing inks on PE surfaces, oxidation of the surface must take place. This can be accomplished either with flame or by corona treatment. Significant off-odors can be produced as a result of the oxidation process. In particular unsaturated ketones and aldehydes are implicated in these off-odors (Chapter 13). 

The threshold limits of chemical compounds can lie over a range of 10 orders of magnitude or more (Table 13-3). The saturated hydrocarbons and organic solvents have high threshold limits and are as a consequence relatively odorless. Esters of acrylic acid and a,fl-unsaturated ketones and aldehydes belong to intensive aroma compounds. 

The perhydroxyl anion, HOf, is a powerful nucleophile (see Chapter 3) and will attack substrates such as electron-deficient olefins (e.g. a,/ -unsaturated ketones) and aldehydes. The perhydroxyl anion is also of value in bleaching and product purification, particularly of natural products. In addition, it can be used to generate more powerful oxidants by mixing with electron-deficient acyl compounds (giving peroxyacids) or with nitriles (Figure 2.5). 

Thermal cyclization reaction of Fischer carbene complexes with a, 3-unsaturated ketones and aldehydes led to 2,3-dihydrofurans, which were converted to the corresponding furans under various conditions, including treatment with silica gel, use of non-aqueous acid (HBF4 or CF3CO2H) or simply by heating <07AGE4136>. 

Table 4.1-3 General infrared and Raman characteristics for estimation of the conformation of a, /3-unsaturated ketones and aldehydes (Oelichmann et al., 1982)...

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