Unsaturated carbonyl compounds chloride

This reaction is the acid-catalyzed counterpart of a 1,4-addition reaction to an a,l3-unsaturated carbonyl compound. Chloride ion, without an acid present, will not add to acrolein. That is, chloride ion is not a strong enough nucleophile to drive the reaction to the right. However, if the carbonyl is protonated, the intermediate cation is a stronger electrophile and will react with chloride ion. 

A particularly useful reaction has been the selective 1,2-reduction of a, P-unsaturated carbonyl compounds to aHyUc alcohols, accompHshed by NaBH ia the presence of lanthanide haUdes, especially cerium chloride. Initially appHed to ketones (33), it has been broadened to aldehydes (34) and acid chlorides (35). NaBH by itself gives mixtures of the saturated and unsaturated alcohols. 

A significant advance in the synthesis of monoorganotin trihaHdes was the preparation of P-substituted ethyl tin trihaHdes in good yield from the reaction of stannous chloride, hydrogen haHdes, and a,P-unsaturated carbonyl compounds, eg, acryHc esters, in common solvents at room temperature and atmospheric pressure (153,154). The reaction is beHeved to proceed through a solvated trichlorostannane intermediate (155) ... 

Epoxidation of aldehydes and ketones is the most profound utility of the Corey-Chaykovsky reaction. As noted in section 1.1.1, for an a,P-unsaturated carbonyl compound, 1 adds preferentially to the olefin to provide the cyclopropane derivative. On the other hand, the more reactive 2 generally undergoes the methylene transfer to the carbonyl, giving rise to the corresponding epoxide. For instance, treatment of P-ionone (26) with 2, derived from trimethylsulfonium chloride and NaOH in the presence of a phase-transfer catalyst Et4BnNCl, gave rise to vinyl epoxide 27 exclusively. ... 

Despite the increasing information on the photochemistry of 2,4-dienones and other unsaturated ketones, as well as on the ring-chain valence isomerism of halogen-substituted pyran and dihydi opyran systems,the data are still very scarce. The intermediate formation of pyrans valence-isomeric with unsaturated carbonyl compounds in the pyridine syntheses based on reactions of ammonia with aldehydes or ketones, advocated by various authors (cf. Section II,B,2,f), is still rather speculative. (See also Section II,B,2,e for the valence isomerism of 5-chloro-2,4-dienones with pyrylium chlorides.)... 

The arylation of alkenes by treatment with a diazonium chloride (or bromide) solution and cupric chloride (or bromide) is called the Meerwein arylation reaction, after its discoverer (Meerwein et al., 1939). Originally, it was discovered using a,P-unsaturated carbonyl compounds, namely coumarin (Scheme 10-43) and cinnamic derivatives (Schemes 10-44 and 10-45). As Scheme 10-45 shows, the Meerwein reac-... 

Rhodium-catalysed addition (10) of hydridosilanes (Chapter 17) to a/3-unsaturated carbonyl compounds can be performed regioselectively, to afford either the product of 1,2-addition, or, perhaps more usefully, that of 1,4-addition, i.e. the corresponding silyl enol ether this latter process is an excellent method for the regiospecific generation of silyl enol ethers. Of all catalyst systems investigated, tris(triphenylphosphine)rhodium(l) chloride proved to be the best. 

Few a-ketosulphoxides 123 were prepared by trapping the enolate anions 124, which are generated by the Michael addition of Grignard reagents to easily available a, -unsaturated carbonyl compounds 125, with methanesulphinyl chloride (equation 65). 

When the conditions are controlled properly, Zn can mediate the reduction of the C-C double bond of a, (3-unsaturated carbonyl compounds in the presence of a nickel catalyst in aqueous ammonium chloride (Eq. 10.7). The use of ultrasonication enhances the rate of the reaction.15 Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of... 

Organylzirconocene derivatives do not show any useful reactivity toward a,[5-unsaturated carbonyl compounds, but the reaction can be promoted by the addition of CuOTf [14], The initial version was stoichiometric in Cu [14], but a Cu-catalyzed version was subsequently developed [112,113]. Adaptation of the Ni salt + DIBAH catalysts for cross-coupling [10] to conjugate addition led to the Ni-catalyzed conjugate addition of alkenylzirconocene chlorides [16,17] (Scheme 1.25). 

The (3-metaloxy radical was first exploited for synthetic purposes in C—H and C—C bond-forming reactions by Nugent and RajanBabu through the use of titanocene(III) chloride as an electron-transfer reagent [5]. They established that the (3-titaniumoxy radicals formed after electron transfer can be reduced by hydrogen atom donors, e. g. 1,4-cy-clohexadiene or tert-butyl thiol, that they add to a,(3-unsaturated carbonyl compounds, and that they can react intramolecularly with olefins in 5-exo cyclizations. 

Many examples of the phase-transfer catalysed epoxidation of a,(3-unsaturated carbonyl compounds using sodium hypochlorite have been reported [e.g. 7-10]. The addition of transition metal complexes also aids the reaction [11], but advantages in reaction time or yields are relatively insignificant, whereas the use of hexaethyl-guanidinium chloride, instead of a tetra-alkylammonium salt, enhances the rate of epoxidation while retaining the high yields (>95%) [10]. Intermediate (3-haloalkanols are readily converted into the oxiranes under basic conditions in the presence of benzyltriethylammonium chloride [12]. 

In order to modulate the reactivity of intermediate 331, it was transformed into its copper derivative by treatment with copper(I) bromide or iodide in THF at —78 °C, and then was allowed to react with a,/3-unsaturated carbonyl compounds (to give compounds 343 resulting from a conjugated addition), acyl chlorides (to give ketones 344) and copper(II) chloride (to dimerize giving compounds 345) (Scheme 100)"° ". ... 

Next to the cyclopropane formation, elimination represents the simplest type of a carbon-carbon bond formation in the homoenolates. Transition metal homoenolates readily eliminate a metal hydride unit to give a,p-unsaturated carbonyl compounds. Treatment of a mercurio ketone with palladium (II) chloride results in the formation of the enone presumably via a 3-palladio ketone (Eq. (24), Table 3) [8], The reaction can be carried out with catalytic amounts of palladium (II) by using CuCl2 as an oxidant. Isomerization of the initial exomethylene derivative to the more stable endo-olefin can efficiently be retarded by addition of triethylamine to the reaction mixture. 

Furan-2-methanols are cleaved to derivatives of levulinic ester by methanolic hydrogen chloride a mechanism involving the carbonium ion (375) has been proposed. Under similar conditions, a,(3- unsaturated carbonyl compounds of type (384) undergo a similar rearrangement, a reaction known as the Marckwald rearrangement, and afford keto esters of type (385), as shown in Scheme 105 in an example drawn from a synthesis of equilenin (70AJC547). 

Dialkoxy-3,4-dihydropyrans are produced under mild conditions from the zinc chloride-catalyzed cycloaddition of a,/8-unsaturated carbonyl compounds with ketene acetals (Scheme 47) (81RTC13). At lower temperatures a [2 + 2]-cycloaddition leads to oxetanes, but on warming these compounds revert to starting materials and thence to the thermodynamically favoured dihydropyrans. 

Lithium diisopropylamide, 163 Phenyl azide-Aluminum chloride, 240 Halo carbonyl compounds (see also Unsaturated carbonyl compounds) a-Chloro acids Sodium nitrite, 282 a-Halo aldehydes and ketones... 

Vinyl substitutions with N,N-dialkylbenzylamine-cyclopalladated complexes have been studied most thoroughly. In the presence of triethylamine the substitution occurs quite selectively with styrene derivatives19 and a,p-unsaturated carbonyl compounds.20 For example, chloride-bridged cyclopalladated NJ4-dimethylbenzylamine dimer and methyl vinyl ketone give 92% of o-dimethylaminomethylbenzalacetone in 1 h at 110 C (equation 6). 

Palladium-Catalyzed Conjugate Reduction of a,s-Unsaturated Carbonyl Compounds with Diphenylsilane and Zinc Chloride Cocatalyst a,B-Dihydro-B-Ionone... 

You met organocopper reagents in Chapter 10 where you saw that they did conjugate additions to a,p-unsaturated carbonyl compounds. Other metals, such as cadmium or manganese, can also be used to make ketones from acid chlorides. 

Oxoindolizines are obtained by reaction of ethyl pyrrolidinylideneacetate with several acyclic unsaturated carbonyl compounds by cyclization of the formed Michael adducts104 (equation 73). When this reaction was modified by changing the ring size of the enaminoester, the substitution pattern of the enone structure and by varying the conditions, different products were isolated105. N-acylation could be accomplished by reaction of acyl chlorides in the presence of pyridine. Bicyclic lactams are yielded by Michael addition of acrylic esters and NaH (equation 74). 

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