Ketone, ammonium => esters

Direct coupling of carbon nucleophiles with 1,3-dinitrobenzene is promoted by ultraviolet irradiation in the presence of quaternary ammonium fluorides, which can act not only as the base to generate the carbon nucleophile, but also as a proton transfer agent in the rearomatization step [83], The dinitrobenzene acts as the electron acceptor in the photochemical step. No reaction occurs in the absence of the fluoride and, surprisingly, although simple ketones, nitriles, esters and fl-kcto esters react, pentan-2,4-dione does not. 

The formation of cyclopropanes from 7C-deficient alkenes via an initial Michael-type reaction followed by nucleophilic ring closure of the intermediate anion (Scheme 6.26, see also Section 7.3), is catalysed by the addition of quaternary ammonium phase-transfer catalysts [46,47] which affect the stereochemistry of the ring closure (see Chapter 12). For example, equal amounts of (4) and (5) (X1, X2 = CN) are produced in the presence of benzyltriethylammonium chloride, whereas compound (4) predominates in the absence of the catalyst. In contrast, a,p-unsatu-rated ketones or esters and a-chloroacetic esters [e.g. 48] produce the cyclopropanes (6) (Scheme 6.27) stereoselectively under phase-transfer catalysed conditions and in the absence of the catalyst. Phenyl vinyl sulphone reacts with a-chloroacetonitriles to give the non-cyclized Michael adducts (80%) to the almost complete exclusion of the cyclopropanes. 

Palladium-catalysed C-C bond formation under Heck reaction conditions, which normally requires anhydrous conditions and the presence of copper(I) salts, is aided by the addition of quaternary ammonium salts. It has been shown that it is frequently possible to dispense with the copper catalyst and use standard two-phase reactions conditions [e.g. 18, 19]. Tetra-/i-butylammonium salts catalyse the palladium-catalysed reaction of iodoarenes with alkynes to yield the arylethynes in high yield [20, 21], whereas the reaction with 3-methylbut-1 -yn-3-ol (Scheme 6.30) provides a route to diarylethynes [22]. Diarylethynes are also formed from the reaction of an iodoarene with trimethylsilylethyne [23], Iodoalkynes react with a,p-unsaturated ketones and esters to produce the conjugated yne-eneones [19],... 

Solvent Dyes (see also Section 3.10). The 1 2 chromium and cobalt complex dyes devoid of any hydrophilic substituent have a considerable solubility in organic solvents, especially alcohols, ketones, and esters. Enhanced solubility can be achieved by converting the metal-complex sodium salts into salts of organic cations [57], Such cations may be cationic dyes, long-chain aliphatic ammonium ions, or protonated guanidines. For example, the bluish red solvent dye 34 reaches a solubility in organic solvents of up to 1000 g/L [58],... 

Mortimer86 has also recommended the two-dimensional method, using ethyl acetate-acetic acid-water and ethyl acetate-formamide-pyridine as developers. Methyl Cellosolve-ethyl methyl ketone-ammonium hydroxide may also be used. Since high content of water and the presence of an alcohol in the solvent mixture gave rise to diffuse spots, formamide was substituted for water. RF values relative to the movement of orthophosphate were determined and found to vary with the distance the solvent moved. Also, in complex mixtures, the presence of some esters resulted in elongation of other ester spots. This effect and the RF variation observed-do not conform to the concept of a liquid-liquid distribution process. 

Alkylation products of pseudoephedrine amides are readily transformed in a single operation into highly enantiomerically enriched carboxylic acids, aldehydes, ketones, lactones or primary alcohols. Alkylated pseudoephedrine amides can be hydrolyzed under acidic or basic conditions to form carboxylic acids. Simply heating a pseudoephedrine amide at reflux in a 1 1 mixture of sulfuric acid (9-18 N) and dioxane affords the corresponding carboxylic acid in excellent chemical yield with little or no epimerization (eq 7). Under these conditions, the substrate initially undergoes a rapid N— -0 acyl transfer reaction followed by rate-limiting hydrolysis of the resulting (3-ammonium ester intermediate to form the carboxylic acid. ... 

The products were readily converted to free 8-amino ketones and esters. Thus, treatment of the products with cerium ammonium nitrate in acetonitrile-water (9 1) at room temperature induced smooth deprotection of the 2-methoxyphenylamino group to give free /5-amino carbonyl compounds [71,72]. 

Pyrroles which have a ketone or ester substituent are more resistant to ring degradation and high-yielding side-chain oxidation can be achieved using cerium(IV) ammonium nitrate, with selectivity for an a-alkyl. ... 

The preparation of yS-enamino ketone and esters on solid montraorillonite KIO day coupled with MW irradiation applies to cydic, acyclic and a-chloro-substituted j8-dicarbonyl compounds with amines or their corresponding ammonium acetates (Scheme 8.26) [80]. 

Unlike the chiral, neutral N-F reagents, the [N-F] ammonium salts of cinchona alkaloids are employed for the fluorination of a number of substrates ketone and ester enolates, (3-keto esters, a-cyano esters, a-nitro esters, a-amino esters, silyl enol ethers, enol acetates, nitrile anions, and... 

The chemistry of indium metal is the subject of current investigation, especially since the reactions induced by it can be performed in aqueous solution.15 The selective reductions of ethyl 4-nitrobenzoate (entry 1), 2-nitrobenzyl alcohol (entry 2), l-bromo-4-nitrobenzene (entry 3), 4-nitrocinnamyl alcohol (entry 4), 4-nitrobenzonitrile (entry 5), 4-nitrobenzamide (entry 6), 4-nitroanisole (entry 7), and 2-nitrofluorenone (entry 8) with indium metal in the presence of ammonium chloride using aqueous ethanol were performed and the corresponding amines were produced in good yield. These results indicate a useful selectivity in the reduction procedure. For example, ester, nitrile, bromo, amide, benzylic ketone, benzylic alcohol, aromatic ether, and unsaturated bonds remained unaffected during this transformation. Many of the previous methods produce a mixture of compounds. Other metals like zinc, tin, and iron usually require acid-catalysts for the activation process, with resultant problems of waste disposal. 

There are a number of methods for the oxidation of primary alcohols or ethers to dimeric esters, and secondary alcohols to ketones. We recently also found that quaternary ammonium tribromides, especially BTMA Br3, are useful oxidizing agents for the purpose described above (ref. 31). 

Selective oxidation of methyl pyrroles 65 possessing an a-carboxylic ester and sensitive p-substituents can be accomplished using cerium triflate in methanol <96TL315>. Moreover, the resultant a-methoxymethylpyrroles 66 may be converted to dipyrrylmethanes 67 in a "one-pot" sequence by treatment with 48% HBr. The dipyrrylmethanes, in turn, can be further oxidized to dipyrryl ketones by ceric ammonium nitrate <96JHC221>. 

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