Alkylation carbonyl compounds

Hydroxymethylation of carbonyl compounds.3 Alkyl chloromethyl ethers react in the presence of Sml2 (2 equiv.) with ketones in THF to give adducts in 50-80% yield. The reaction with aldehydes is conducted in tetraethylene glycol dimethyl ether, which suppresses pinacol reduction. Hydroxymethylation of carbonyl compounds can be effected by use of benzyl chloromethyl ether followed by hydrogenolysis of the adduct. 

The principal synthetic application of lithium dialkylcuprate reagents is their reaction with a,p-unsatu-rated carbonyl compounds. Alkylation of the p carbon occurs. 

A clear division of Paterno-Biichi reactions into several distinct categories is possible on the basis of the type of reacting carbonyl compound (alkyl or aromatic), the excited state responsible for reaction (n—71 or Ti—n, singlet or triplet), and the type of olefin (electron deficient or electron-rich). Some examples of these reactions are given in Eqs. 7—11, where only the oxetane products are shown. 

In the present paper we have studied four acid catalyzed reaotions involving carbonyl compounds alkylation of benzene with formaldehyde, esterification of phenylacetic acid, Friedel-Crafts acylation by phenylpropanoyl chloride, and the cross aldolic condensation of acetophenone with benzaldehyde in the presence of three Hp zeolites with different framework Si-to-Al... 

We introduced the chemistry of malonate esters in Chapters 21 and 26 as a useful way of controlling the enolization of carbonyl compounds. Alkylation followed by decarboxylation means that we can treat acetoacetate and malonate esters as equivalent for these synthons. 

Whereas isolated imines are relatively unstable and readily undergo hydrolysis to form carbonyl compounds, alkylated imines and imino derivatives are found as stable compounds in a variety of situations. Thus a number of nitrogen derivatives of aldehydes and ketones, such as the oxime, semicarbazone and hydrazone, contain an imino fragment. 

Carbonyl compound alkylations. Allylic alcohols and homoallylic silyl ethers are prepared from alkynes and dienes, respectively. 

Three-component coupling in high yield has been achieved by irradiation of a mixture of a,/funsaluraled carbonyl compounds, alkyl hahdes, and aUyltriphenyl-leads (Scheme 13.25) [48]. Addition of a catalytic amount of hexaphenyldilead accelerated the reaction, and alkyl bromides gave better yields than alkyl iodides. When allyltributyltin was used in the place of allyltriphenyUead, however, yields of the product did not exceed 60% under a variety of conditions. 

The selenium-stabilized carbanions formed react with a variety of electrophiles such as carbonyl compounds, alkyl halides, epoxides, etc., transforming them into several functional groups, as exemplified in Scheme 15.73 [153]. 

Entry Carbonyl compound Alkyl iodide Product Yield E Z... 

Since organoaluminums are highly oxophilic, the reaction of organoaluminum compounds and various carbonyl compounds gives 1 1 Lewis acid-base complexes. In the cases of alkylaluminums and electrophilic carbonyl compounds, alkyl transfer reactions to carbonyl carbon proceed via Lewis acid-base complexes at high temperature [37, 38]. 

The reaction of lithiated cumulenic ethers with ethylene oxide, trimethyl-chlorosilane and carbonyl compounds shows the same regiosnecificity as does the alkylation. 

If boranes (K. Utimoto, 1973 H.C. Brown, 1975, 1980 A. Pelter, 1979) are used as donor synthons for the alkylation of a, -unsatarated carbonyl compounds, no enolate anion is formed, and the, 8-position of the C=C bond is the only reaction site. 

The Julia-Lythgoc olefination operates by addition of alkyl sulfone anions to carbonyl compounds and subsequent reductive deoxysulfonation (P. Kocienski, 1985). In comparison with the Wittig reaction, it has several advantages sulfones are often more readily available than phosphorus ylides, and it was often successful when the Wittig olefination failed. The elimination step yields exclusively or predominantly the more stable trans olefin stereoisomer. 

The only common synthons for alkynes are acetylide anions, which react as good nucleophiles with alkyl bromides (D.E. Ames, 1968) or carbonyl compounds (p. 52, 62f.). 

Various organotin reagents react with acyl and aroyl halides under mild conditions without decarbonylation to give carbonyl compounds[390,39l]. Alkyl- or alkenyltin reagents react with acyl and aroyl chlorides to give ketones[548.733,734]. One example is the preparation of the a,/3-dnsaturated 7-keto esters 860 and 861, carried out under a CO atmosphere[735]. The reaction has been applied intramolecularly to the synthesis of the macrocyclic keto... 

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