Summary of Aldehyde and Ketone Addition Reactions

The nucleophilic addition reactions of aldehydes and ketones occurring at the carbonyl carbon atom that we have studied so far are summarized below. In Chapters 18 and 19 we shall see other examples. 

Specific Example Using a Grignard Reagent (Section 12.7C) 

Specific Examples Using Metal Hydrides (Section 12.3) 

Addition of Hydrogen Cyanide (Section 16.9) General Reaction 

The key terms and concepts that are highlighted in bold, blue text within the chapter are PLU S defined in the glossary (at the back of the book) and have hyperlinked definitions in the accompanying WUeyPLUS course (www.wileyplus.com). 

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A summary of nucleophilic addition reactions of aldehydes and ketones. 

Mills and coworkers (37) performed a series of MPV reductions of cyclic ketones to the corresponding epimeric mixtures of alcohols using aluminum isopropoxide as the catalyst in isopropyl alcohol. A summary of their results is given in Table 2. They conclude that the predominant influence in these reductions pertinent to the cis/trans ratio of the resulting epimeric alcohol mixtures is the degree of steric hindrance of the carbonyl moiety. They also separately investigated (38) a series of MPV reductions of aldehydes and unstable ketones where slow, drop-wise addition of the carbonyl substrate to the reactions inproved the yields. 

Summary of the Relationship between Diastereoselectivity and the Transition Structure. In this section we considered simple diastereoselection in aldol reactions of ketone enolates. Numerous observations on the reactions of enolates of ketones and related compounds are consistent with the general concept of a chairlike TS.35 These reactions show a consistent E - anti Z - syn relationship. Noncyclic TSs have more variable diastereoselectivity. The prediction or interpretation of the specific ratio of syn and anti product from any given reaction requires assessment of several variables (1) What is the stereochemical composition of the enolate (2) Does the Lewis acid promote tight coordination with both the carbonyl and enolate oxygen atoms and thereby favor a cyclic TS (3) Does the TS have a chairlike conformation (4) Are there additional Lewis base coordination sites in either reactant that can lead to reaction through a chelated TS Another factor comes into play if either the aldehyde or the enolate, or both, are chiral. In that case, facial selectivity becomes an issue and this is considered in Section 2.1.5. 

Summary Syntheses of Ketones and Aldehydes 837 18-11 Reactions of Ketones and Aldehydes Introduction to Nucleophilic Addition 839... 

In studying reactions of other functional groups, we have already encountered some of the best methods for making ketones and aldehydes. Let s review and summarize these reactions, and then consider some additional synthetic methods. A summary table of syntheses of ketones and aldehydes begins on page 837. 

Summary (Aminomethyl)silanes have been prepared by new synthetic routes starting from lithiosilanes or (lithiomethyl)amines. (Lithiomethyl)(aminomethyl)silanes were formed by metallation with lithioalkyls. A sulfur-substituted (lithiomethyl)(aminomethyl)silane and a THF adduct are characterized by single crystal X-ray diffraction. In reactions of (lithiomethyl)(aminomethyl)silanes with aldehydes or ketones no clear addition/depro-tonation profile was observed. 

In summary, the uncatalysed oxidation of hydrocarbons at temperatures of up to 120°C leads to alkylhydroperoxides, ROOH, dialkylperoxides, ROOR, alcohols, ROH, aldehydes, RCHO and ketones, RR C=0. In addition, cleavage of a dihydroperoxide II of Reaction (4.4) leads to diketones, RCO(CH2)jCOR keto-aldehydes, RCO(CH2)jCHO, hydroxy ketones, RCH(OH)-(CH2)jCOR and so forth. Under metal-catalysed conditions or at higher temperatures, considered in Sections 4.2.2 and 4.2.3, degradation leads to a complex mixture of final products. 

In summary, most of the known synthetic routes to azaadamantanes depend on condensation of an amine or ammonia with a carbonyl compound or equivalent (aldehyde, ketone, ortho ester, acetal) or other active methylene compound, such as nitromethane. The syntheses of 10 and 13 employed bromo intermediates in displacement or addition reactions. 

In Summary Treatment of enolizable aldehydes with catalytic base leads to jS-hydroxy aldehydes at low temperature and to a,jS-unsaturated aldehydes upon heating. The reaction proceeds by enolate attack on the carbonyl function. Aldol addition to a ketone carbonyl group is energetically unfavorable. To drive the aldol condensation of ketones to product, special conditions have to be used, such as removal of the water or the aldol formed in the reaction. 

In Summary Acyl chlorides are attacked by a variety of nucleophiles, the reactions leading to new carboxylic acid derivatives, ketones, and aldehydes by addition-elimination mechanisms. The reactivity of acyl halides makes them useful synthetic relay points on the way... 

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