Addition reactions to carbonyl compounds

Likewise thioacetals have been prepared in yields between 60 to 99% by treatment of aldehydes or ketones with 1,2-ethanethiol in the presence of Zeolite HSZ-360, a dealuminated Y-Zeolite [101]. Many other functional groups like al-kenes, tetrahydropyranyl and nitriles are tolerated under the mild reaction conditions. 

DOLate was formed which was tested in the Lewis acid catalyzed enantioselective addition of diethylzinc to benzaldehyde. The authors note that the catalyst can be recovered by simple filtration and was active for at least more than twenty runs (refer also to Section 4.2.3) [102]. 

Other examples involved the use of chiral Schiff base-zinc complexes as catalysts [33 a] and polymer-supported chiral N-tritylaziridino alcohols as catalysts. The stereoselectivity was reported to be up to 97% ee for aUphatic and up to 96% ee for aromatic aldehydes [103]. 

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Azirine, trans-2-methyl-3-phenyl-racemization, 7, 33, 34 1-Azirine, 2-phenyl-reactions, 7, 69 with carbon disulfide, S, 153 1-Azirine, 3-vinyl-rearrangements, 7, 67 Azirines, 7, 47-93 cycloaddition reactions, 7, 26 fused ring derivatives, 7, 47-93 imidazole synthesis from, 5, 487-488 photochemical addition reactions to carbonyl compounds, 7, 56 photolysis, 5, 780, 7, 28 protonated... 

We have intentionally selected example reactions (Figs. 29-33) that would not usually be immediately obvious to a chemist. The examples chosen have all been concerned with rearrangements of various types, since their courses are frequently difficult to predict. It remains to emphasize that the reactivity functions contained in EROS perform perfectly well with other types of reaction. This is true, for example, with reactions that a chemist could derive directly from an analysis of the functional groups in a molecule. Thus, EROS predicts addition reactions to carbonyl compounds, nucleophilic substitutions, and condensation reactions, to name just a few examples. In all these reaction types, the possibility of assigning a quantitative estimate to the reactivity at the various sites via the reactivity functions is of particular merit. It... 

Addition and Conjugate Addition Reactions to Carbonyl Compounds... 

The equilibrium position of addition reactions to carbonyl compounds is also influenced by electronic substituent effects, as was also shown in Figure 9.1 ... 

Even the very efficient enantioselective catalysts used in organozinc addition reactions to carbonyl compounds failed to catalyze the corresponding addition reactions to nonactivated imines such as A-silyl-, A-phenyl-, or iV-benzyl-imines. However, enantioselective additions of diaUcylzinc compounds to more activated imines, like iV-acyl- or iV-phosphinoyl-imines, in the presence of catalytic or stoichiometric amounts of chiral (see Chiral) aminoalcohols, have been recently reported. For example, in presence of 1 equiv of (A,A-dibutylnorephedrine) (DBNE) diethylzinc reacts with masked A-acyl imines like A-(amidobenzyl)benzotriazoles, to give chiral A-(l-phenylpropyl)amides with up to 76% e.e. (equation 68). 

The chemistry of amines is dominated by the nucleophilicity of the nitrogen atom. Amines form salts, participate in nucleophilic substitution reactions of alkyl halides and in nucleophilic addition reactions to carbonyl compounds. 

Many aryl nitriles are obtained from diazonium salts by treatment with copper(l) cyanide. Hydroxy and amino nitriles are obtained from addition reactions to carbonyl compounds. 

In addition reactions to carbonyl compounds C-3 attack generally predominates,as illustrated in Scheme 72 with the formation of vinylsilane (163). C-1 addition also predominates in alkylation and acylation reactions involving a-silylallyl anions when alkyl halides and acyl halides are used as electrophiles. 

In the presence of cationic gold catalysts, 1,6-enynes with a terminal double bond undergo intermolecular addition reactions to carbonyl compounds. Again, a skeletal rearrangement of the gold carbene intermediate is the key to the formation of the tricyclic heterocycles. 

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