Unsaturated carbonyl compounds conjugate addition

The anion of an aldehyde dithioacetal 5-oxide is well known to add to a,3-unsaturated carbonyl compounds. " Conjugate addition of formaldehyde di-p-tolyl dithioacetal 5-oxide (114) to open-chain and cyclic enones is achieved by using HMPA as a polar cosolvent in THF (-78 C)." The lithio derivative of (5)-(114) was found to add to 2-cyclopentenone with asymmetric induction. Transformation of the dithioacetal part into a formyl group gives 3-formylcyclopentanone in 39% enantiomeric excess (equation 28)." Interestingly, highly asymmetric induction is observed in the conjugate addition of the... 

Trialkylstannyl-lithium reacts with secondary alkyl halides (substitution) and with a/S-unsaturated carbonyl compounds (conjugate addition) to give alkyl tin derivatives which may be oxidized with chromic anhydride in pyridine to give a saturated ketone. Applying the procedure to a cycloalkenone, an efficient dialkyl-ative enone transposition can be realized (Scheme 68). ... 

An empirical increment system permits prediction of charge distribution in a,/ -unsaturated carbonyl compounds, assuming additivity of electronic effects and neglecting the conformational dependence of carbon-13 chemical shifts [290]. Moreover, carbonyl and alkenyl carbon shifts of a, /3-unsaturatcd ketones may be used to differentiate between planar and twisted conjugated systems, as shown in Table 4.29 [291] and outlined for phenones in Section 3.1.3.8. 

The RuH2(PPh3)4-catalyzed addition of active methylene compounds can also be applied to conjugate additions to a,/3-unsaturated carbonyl compounds (Michael additions). In 1989, Murahashi reported the first example of the transition metal-catalyzed Michael addition of active methylene compounds [74]. One of the notable advances of this catalytic reaction is that the addition of C-H bonds to a,/3-unsaturat-ed carbonyl compounds give Michael adducts without contamination by the corresponding aldol products (Eq. 9.56) [74]. Recently, Murahashi applied their aldol and Michael addition reactions to a solid-phase synthesis using polymer-supported nitriles (Scheme 9.12) [76]. In this case, four component reactions took place with high diastereoselectivity. 

Addition of dihydrosilane to a, /J-unsaturated carbonyl compounds such as citral (49), followed by hydrolysis, affords saturated citroneJlal (50) directly. The reaction is used for the selective reduction of conjugated double bonds[45,46]. In addition to Pd catalyst, the use of a catalytic amount of... 

CONJUGATE ADDITION OF ORGANOCOPPER REAGENTS TO a,p-UNSATURATED CARBONYL COMPOUNDS... 

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... 

Ammonia and amines undergo conjugate addition to a 3 unsaturated carbonyl compounds (Section 18 12) On the basis of this information predict the pnncipal organic product of each of the following reactions... 

Acrolein (H2C=CHCH=0) undergoes conjugate addition with sodium azide in aqueous solution to give N3CH2CH2CH=0 Propanal is not an a 3 unsaturated carbonyl compound and cannot undergo conjugate addition... 

Methacryhc acid and its ester derivatives are Ctfjy -unsaturated carbonyl compounds and exhibit the reactivity typical of this class of compounds, ie, Michael and Michael-type conjugate addition reactions and a variety of cycloaddition and related reactions. Although less reactive than the corresponding acrylates as the result of the electron-donating effect and the steric hindrance of the a-methyl group, methacrylates readily undergo a wide variety of reactions and are valuable intermediates in many synthetic procedures. 

In the presence of suitable a,/5-unsaturated carbonyl compounds (3) the nucleophilic methylide (2) undergoes conjugate addition followed by expulsion of dimethyl sulfoxide to give cyclopropanes (5). 

Conjugate addition (Sections 10.10 and 18.12) Addition reaction in which the reagent adds to the termini of the conjugated system with migration of the double bond synonymous with 1,4 addition. The most common examples include conjugate addition to 1,3-dienes and to a,(3-unsaturated carbonyl compounds. 

The 1,4-addition of an enolate anion 1 to an o ,/3-unsaturated carbonyl compound 2, to yield a 1,5-dicarbonyl compound 3, is a powerful method for the formation of carbon-carbon bonds, and is called the Michael reaction or Michael addition The 1,4-addition to an o ,/3-unsaturated carbonyl substrate is also called a conjugate addition. Various other 1,4-additions are known, and sometimes referred to as Michael-like additions. 

Enamines react with acceptor-substituted alkenes (Michael acceptors) in a conjugate addition reaction for example with o ,/3-unsaturated carbonyl compounds or nitriles such as acrylonitrile 8. With respect to the acceptor-substituted alkene the reaction is similar to a Michael addition ... 

The conjugate addition of a nucleophile to an a,fi-unsaturated aldehyde or ketone is caused by the same electronic factors that are responsible for direct addition. The electronegative oxygen atom of the a,/3-unsaturated carbonyl compound withdraws electrons from the /3 carbon, thereby making it electron-poor and more electrophilic than a typical alkene carbon. 

Exactly the same kind of conjugate addition can occur when a nucleophilic enolate ion reacts with an ,j6-unsaturated carbonyl compound—a process known as the Michael reaction. 

Conjugate addition (Section 19.13) Addition of a nucleophile to the (3 carbon atom of an a./3-unsaturated carbonyl compound. 

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