Addition reactions 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... 

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

The reduction of carbonyl compounds by reaction with hydride reagents (H -) and the Grignard addition by reaction with organomagnesium halides (R - +MgBr) are examples of nucleophilic carbonyl addition reactions. What analogous product do you think might result from reaction of cyanide ion with a ketone ... 

Reactions 11-22-11-26 involve the introduction of a CH2Z group, where Z is halogen, hydroxyl, amino, or alkylthio. They are all FriedeI-Crafts reactions of aldehydes and ketones and, with respect to the carbonyl compound, additions to the C=0 double bond. They follow mechanisms discussed in Chapter 16. 

Among the olefination reactions, those of phosphonium ylides, phosphonate anions, silylmethyl anions, and sulfone anions are discussed. This chapter also includes a section on conjugate addition of carbon nucleophiles to a, (J-unsaturated carbonyl compounds. The reactions in this chapter are among the most important and general of the carbon-carbon bond-forming reactions. 

Among all the nucleophilic addition reactions of carbonyl compounds, allylation reaction has been the most successful, partly due to the relatively high reactivity of allyl halides. Various metals have been found to be effective in mediating such a reaction (Scheme 8.4). Among them, indium has emerged as the most popular metal for such a reaction. 

Wu et alP have synthesized a TSIL having 2,2,6,6-tetramethylpiper-idine-l-oxyl (TEMPO) appended to an imidazolium cation for the oxidation of alcohols to corresponding carbonyl compounds. These reactions have shown high yields similar to non-supported TEMPO, but with the additional advantage of easy separation of products. 

Addition of phosphorus ylide to carbonyl compounds Wittig reaction... 

In the case of pyrroles with a,P-unsaturated carbonyl compounds, the reactions have low selectivity because these substrates are excellent nucleophiles, thus twofold addition products are mainly obtained [73, 74]. 

Conjugate additions to enals and enones.1 In the presence of zinc (or tin) allyl halides undergo 1,2-addition to carbonyl compounds. The reaction is facilitated by sonication and proceeds in highest yield in saturated aqueous ammonium chlo-ride/THF (5.1).1... 

Addition of NaX or BuJNX to l-alkyn-3-ones.1 In the presence of these two reagents, sodium or ammonium salts undergo conjugate addition to acetylenic carbonyl compounds. This reaction provides mm-P-halovinyl ketones or N,N-diethyl m-P-haloacrylamides. 

In this section as well as in Section 10.5.3, carbonyl compounds that contain a stereocenter in the position a to the C=0 group are referred to succinctly with the term oc-chiral carbonyl compound. Because of the presence of the stereocenter, the half-spaces on both sides of the plane of the C=0 double bond of these compounds are diastereotopic. In this section, we will study in detail stereogenic addition reactions of hydride donors to the C=0 double bond of oc-chiral carbonyl compounds. Additions of this type can take place faster from one half-space than from the other—that is, they can be diastereoselective. 

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