Nucleophilic addition to a carbonyl

Like a carbonyl group, a nitrile group is strongly polarized and has an electrophilic carbon atom. Nitriles therefore react with nucleophiles to yield 5p2-hybridized imine anions in a reaction analogous to the formation of an sp3-hybridized alkoxide ion by nucleophilic addition to a carbonyl group. 

Until then, only heterogeneous catalyst had been successful. However, in the mid-1980s, the work of Ito et al. led to an outstanding discovery in a catalytic asymmetric aldol reaction. In this case, enantioselectivity was given by a chiral ferrocene diphosphine ligand, with a carbon nucleophile addition to a carbonyl... 

The 1,2-migration of a silicon moiety to the oxygen anion of a carbon-oxygen single bond produced by nucleophilic addition to a carbonyl group (Brook... 

We have already discussed in Chapter 2 that nucleophilic addition to a carbonyl group is controlled by stereoelectronic effects. Both X-ray data and theoretical calculations indicate a clearly defined path (cf. p.32) for the attack of a nucleophile on a carbonyl group. Baldwin (1) has also used a vector analysis approach to predict the stereochemistry of the addition products. 

Although in the above paper MeS- was studied, MeO- was not, but the latter has now been investigated in detail. Lehn149 and co-workers computed the PE surface for the simplest nucleophilic addition to a carbonyl group, i.e. reaction (8). A... 

Studies of Felkin s model have shown that the transition state for nucleophilic addition to a carbonyl compound is strongly stabilized when the C2-X and Nu- Cj bonds are antiperiplanar.41 Let us apply this rule to a configurationally rigid cyclohexanone. 

These nucleophilic additions to a carbonyl group were also used to synthesize a germene by Peterson s reaction (equation 169)180. 

Nitration of an Arene Section 17.4 Figure 17.3 Nucleophilic Addition to a Carbonyl Group ... 

You met nucleophilic addition to a carbonyl group on p. 114 and 119, where we showed you how cyanide reacts with acetone to give an alcohol. As a reminder, here is the reaction again, with its mechanism. 

The product of nucleophilic addition to a carbonyl group is not always a stable compound... 

The first reaction that you met in this book, in Chapter 2, was the nucleophilic addition to a carbonyl group. Yet we have shown you no examples of radicals adding to carbonyl groups. This typical reaction of polar reagents is really quite rare with radicals. 

Nucleophilic addition to a carbonyl compound to yield an alcohol (Secs. 17.5,19.7)... 

Reactions that modify the side chains of TMM complexes have been examined. Nucleophilic addition to a carbonyl adj acent to the TMM ligand oc curs with high diastereoselectiv-ity (equation 45) 261,274,276 nucleophilic substitution... 

The model correctly predicts (rationalizes) the observed preference for formation of Ae anti raAer than Ae syn product in the cycloaddition reactions of a wide variety of chiral allylic eAers, Aus successfully laying to rest years of frustrated discussion. - It also correctly predicts Aat as Ae size of R increases (Me - Ph < Et < Pr < Bu ), Ae preference for transition state structure (18 ) should increase leading to enhanced anti stereoselectivity (Table 15). At first, Ais prediction seems strange. However, once it is realized Aat, like Ae Felkin-Anh model for nucleophilic addition to a carbonyl, Ae outside position is actually more sterically demanAng Aan Ae inside, Aen Ae prediction is sensible on purely steric grounds. Thus, Ae angle d approach of Ae nitrile oxide oxygen to Ae alkene actually places it nearer Ae outside Aan Ae inside substituent located at Ae allylic carbon. ... 

A less common route involves the further reduction of the ketyl radical anion to the corresponding dianion and subsequent nucleophilic addition to a carbonyl group. 

Acetal formation thus involves (a) nucleophilic addition to a carbonyl group, and (b) ether formation via a carbonium ion. 

Problem 21.12 In acid-catalyzed aldol condensations acid is believed to perform two functions to catalyze conversion of carbonyl compound into the enol form, and to provide protonated carbonyl compound with which the enol can react. The reaction that then takes place can, depending upon one s point of view, be regarded either as acid-catalyzed nucleophilic addition to a carbonyl group, or as electrophilic addition to an alkene. On this basis, write all steps in the mechanism of acid-catalyzed aldol condensation of acetaldehyde. In the actual condensation step, identify the nucleophile and the electrophile. 

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