Conjugated carbonyl compound

Comprehensive Organic Reactions in Aqueous Media, Second Edition, by Chao-Jun 

In addition to the use of hydrogen directly, hydrogen generated from CO and water (water-gas shift reaction) is also very effective in hydrogenating activated alkenes under basic conditions (Fq. 10.3).  

Interestingly, selenium can also catalyze such a reaction with or without (Eq. 10.4) using a base. 

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For conjugated carbonyl compounds, such as a,) -enones, the orbital diagram would be similar, except for the recognition that the HOMO of the ground state is ij/2 of the enone system, rather than the oxygen lone-pair orbital. The excited states can sometimes be usefully represented as dipolar or diradical intermediates ... 

Lewis-acid catalyzed inverse electron-demand Diels-Alder reactions between conjugated carbonyl compounds and simple alkenes and enolethers also allow dihydropyranes to be prepared. SnCU-Catalyzed cycloaddition of... 

In certain cases, Michael reactions can take place under acidic conditions. Michael-type addition of radicals to conjugated carbonyl compounds is also known.Radical addition can be catalyzed by Yb(OTf)3, but radicals add under standard conditions as well, even intramolecularly. Electrochemical-initiated Michael additions are known, and aryl halides add in the presence of NiBr2. Michael reactions are sometimes applied to substrates of the type C=C—Z, where the co-products are conjugated systems of the type C=C—Indeed, because of the greater susceptibility of triple bonds to nucleophilic attack, it is even possible for nonactivated alkynes (e.g., acetylene), to be substrates in this... 

In the presence of a base such as l,4-diazabicyclo[2.2.2]octane (DABCO) or tri-alkylphosphines, conjugated carbonyl compounds such as esters and amides add to aldehydes via the a-carbon to give a-alkenyl-P-hydroxy esters or amides. This sequence is called the Baylis-Hillman reaction and a simple example is... 

Ordinary Grignard reagents react with a, -unsaturated carbonyl compounds and afford both 1,2-adduct and 1,4-adduct. However, methylsulfonyhnethylmagnesium bromide or p-tolylsulfonylmethylmagnesium bromide gave only 1,2-adducts in the reaction with conjugated carbonyl compounds such as crotonaldehyde, cinnamaldehyde, trans-4-phenyl-3-buten-2-one, benzalacetophenone and l,5-diphenyl-2,4-pentadien-l-one. 

J. Fastrez, Estimation of the Free Energies of Addition of Nucleophiles to Conjugated Carbonyl Compounds and to Acyl Derivatives, J. Am. Chem. Soc. 1977, 99, 7004. 

The allylic alcohols that are the initial oxidation products can be further oxidized to carbonyl groups by Se02 and the conjugated carbonyl compound is usually isolated. If the alcohol is the desired product, the oxidation can be run in acetic acid, in which case acetate esters are formed. 

Luche reported that when a zinc-copper couple was used, alkyl halides reacted with conjugated carbonyl compounds and nitriles to give 1,4-addition products in good yields under sonication conditions (Eq. 10.26).57... 

The hydrocyanation of conjugated carbonyl compounds is a related reaction.83 Very often such a conjugated addition is carried out in aqueous conditions. For example, in the pioneer work of Lapworth, hydrocyanation of activated olefins was carried out with KCN or NaCN in aqueous ethanol in the presence of acetic acid (Eq. 10.36).84... 

Reduction of conjugated carbonyl compounds using stoichiometric amounts of the ammonium salt shows little advantage over the sodium salt in acidic methanol [11] with both reagents producing allylic alcohols (58-88% for acyclic compounds and 15-64% for cyclic compounds) by selective 1,2-reduction of the conjugated systems. Aldehydes, ketones and conjugated enones are also reduced by tetra-n-butylammonium cyanoborohydride in HMPA [11, 12], whereas haloalkanes and alkanesulphonic esters are cleaved reductively under similar conditions [13]. 

The radical-ion probe (26) has been used mechanistically to investigate the addition of Grignard reagents to conjugated carbonyl compounds (Scheme 20). ° Reaction of... 

Empirical rules (Woodward s Rules) of good predictive value are available to estimate the positions of the absorption maxima in conjugated alkenes and conjugated carbonyl compounds. 

Hydroboration, 13, 1 Hydrocyanation of conjugated carbonyl compounds, 25, 3 Hydroformylation, 56, 1 Hydrogenation catalysts, homogeneous, 24, 1... 

Fuel components possessing conjugated olefins, conjugated carbonyl compounds, or any combination of chromophores or auxochromes can be the source of color bodies in fuel. Examples are provided in TABLE 4-9. ... 

Planar Conjugated Carbonyl Compounds Charge-Transfer or 1La bands)... 

NUCLEOPHILIC ADDITION TO CONJUGATED CARBONYL COMPOUNDS MICHAEL 3,4-ADDITION... 

The formation of an oxirane from the reaction of dimethylsulfonium methylide with conjugated carbonyl compounds was applied to... 

Conjugate carbonyl compounds contain centers of different hardness (hard Co and soft C=C), consequently hard hydrides favour conversion of enones to allylic alcohols [25]. Such a concept could be operative also in our case since C=C bond is preferably reduced on going from Mgo to SrO. 

Use of proline as a catalyst has become an important methodology in the catalytic asymmetric addition of stabilized carbanions to conjugated carbonyl compounds. Hannessian employed L-proline (S)-l in the addition of nitroalkanes to enones (Scheme 1) [5]. In the presence of 3-7 mol % of (S)-l and an excess of trans-2,5-dimethylpiperazine in chloroform, comparable or higher enantiose-lectivities were attained compared to the Yamaguchi s method using L-proline... 

Nagata, W. Voshioka, M. "Hydrocyanation of Conjugated Carbonyl Compounds in Organic Reactions" Wiley New York, N.Y., 1977, 25, 255. 

Deprotonation of BSMA imines followed by trapping with an electrophile of the intermediate anion has been described (see Section IV.C.4). However, when these imines derive from conjugated carbonyl compounds, attack of the base takes place at the end of the conjugated system to give delocalized bis(allyl) anion that could be alkylated or silylated in the (3-position from the nitrogen.227... 

W. Nagata, M. Yoshioka, Hydrocyanation of Conjugated Carbonyl Compounds, Org. React. 1977, 25, 255-476. 

The C=C absorption of a conjugated carbonyl compound may not be apparent in the IR spectrum because it is so much weaker than the C=0 absorption. The presence of the C = C double bond can still be inferred from its effect on the C=0 frequency and the presence of unsaturated =C—H absorptions above 3000 cm-1. 

Conjugated carbonyl compounds have characteristic 7r — 7r absorptions in the UV spectrum. 

It is not necessary to have two carbon-carbon double bonds in order to have a conjugated system—the C-C and C-0 double bonds of propenal (acrolein) are also conjugated. The chemistry of such conjugated carbonyl compounds is significantly different from the chemistry of their component parts (Chapter 10). 

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