Acetic as reactant

The Mukaiyama aldol reaction can provide access to a variety of (3-hydroxy carbonyl compounds and use of acetals as reactants can provide (3-alkoxy derivatives. The issues of stereoselectivity are the same as those in the aldol addition reaction, but the tendency toward acyclic rather than cyclic TSs reduces the influence of the E- or Z-configuration of the enolate equivalent on the stereoselectivity. 

Scheme 10.2 gives some examples of ene and carbonyl-ene reactions. Entries 1 and 2 are thermal ene reactions. Entries 3 to 7 are intermolecular ene and carbonyl-ene reactions involving Lewis acid catalysts. Entry 3 is interesting in that it exhibits a significant preference for the terminal double bond. Entry 4 demonstrates the reactivity of methyl propynoate as an enophile. Nonterminal alkenes tend to give cyclobutenes with this reagent combination. The reaction in Entry 5 uses an acetal as the reactant, with an oxonium ion being the electrophilic intermediate. 

Early studies of the cobalt hydroformylation (4) included vinyl acetate as the olefinic reactant. A mixture of a- and /3-formyl esters was reported. 

Initially, a reaction of A-acetoxy-A-butoxybenzamide 25c with A-methyl aniline 61 in butyl benzoate 63(R = Bu) and acetic acid. Close examination of these highly coloured reaction mixtures indicated the presence of crystals of A,A-dimethyl-A,A-diphenyltetrazene 65 (Scheme 11, R = Bu). The reaction is promoted by polar solvents as reactants are unchanged in pure acetonitrile. A crossover experiment using a mixture of /V- a ce t o x y - A-- b u t o x y - to 1 u a m i d e 26d and A-acetoxy-A-ethoxybenz-amide 25a afforded clean yields of butyl /Moluatc and ethyl benzoate thus pointing to an intramolecular rearrangement.41... 

The reaction is best carried out in the appropriate anhydrous aldehyde or ketone, which thus functions as reactant and solvent, or in ethanol, in the presence of an optimum of 1.5 equivalents of strong acid per equivalent of arylbiguanide (base). Acetic acid as a catalyst produces, anomalously, the "base-catalysed anilino-triazines (126, 443). The reaction time varies from one hour to two weeks. The rates diminish in the following order ... 

In the above-mentioned example of the polymer-analogous saponification of poly(vinyl acetate) the reactant and the product differ in their properties, for example, in their solubility however, both compounds have the same average degree of polymerization. The poly(vinyl alcohol) obtained by saponification can, in principle, be esterified back to poly(vinyl acetate) with the original molecular weight the reacetylated polymer then has the same properties as the original material. The viscosity number may be used to check whether in fact any chain scission has occurred during the reaction sequence of saponification and reacetylation (see Example 5-1). 

In 2007, another departure from carbonyl-type activation was marked by Kotke and Schreiner in the organocatalytic tetrahydropyran and 2-methoxypropene protection of alcohols, phenols, and other ROH substrates [118, 145], These derivatives offered a further synthetically useful acid-free contribution to protective group chemistry [146]. The 9-catalyzed tetrahydropyranylation with 3,4-dihydro-2H-pyran (DHP) as reactant and solvent was described to be applicable to a broad spectrum of hydroxy functionalities and furnished the corresponding tetrahydro-pyranyl-substituted ethers, that is, mixed acetals, at mild conditions and with good to excellent yields. Primary and secondary alcohols can be THP-protected to afford 1-8 at room temperature and at loadings ranging from 0.001 to 1.0mol% thiourea... 

For both reactions a RhCl3/CH3l/TPO catalyst in acetic acid as reaction solvent affords propionic acid in more than 80 % yield according to the respective stoichiometries of Equations 12 and 13. Although acetic acid is present in excess in the reaction medium, it does not participate in the homologation as reactant. Only traces of propionic acid are produced in the absence of methyl acetate, ethyli-dene diacetate or acetic anhydride under our reaction conditions. Homologation of carboxylic acids has been reported by Knifton (10) to require more severe reaction conditions (220 °C, > 100 bar). 

The present procedures illustrate general methods for the use of preformed lithium enolates5 as reactants in the aldol condensation6 and for the quenching of alkali metal enolates in acetic anhydride to form enol acetates with the same structure and stereochemistry as the starting metal enolate.7 The aldol product, [Pg.55]

Methods (i) and (ii) require palladium(II) salts as reactants. Either palladium acetate, palladium chloride or lithium tetrachloropalladate(II) usually are used. These salts may also be used as catalysts in method (iii) but need to be reduced in situ to become active. The reduction usually occurs spontaneously in reactions carried out at 100 °C but may be slow or inefficient at lower temperatures. In these cases, zero valent complexes such as bis(dibenzylideneacetone)palladium(0) or tetrakis(triphenylphos-phine)palladium(O) may be used, or a reducing agent such as sodium borohydride, formic acid or hydrazine may be added to reaction mixtures containing palladium(II) salts to initiate the reactions. Triarylphosphines are usually added to the palladium catalysts in method (iii), but not in methods (i) or (ii). Normally, 2 equiv. of triphenylphosphine, or better, tri-o-tolylphosphine, are added per mol of the palladium compound. Larger amounts may be necessary in reactions where palladium metal tends to precipitate prematurely from the reaction mixtures. Large concentrations of phosphines are to be avoided, however, since they usually inhibit the reactions. 

A few recent examples of related C-C bond-forming reactions, all involving a palladium-catalyzed C-H activation step at arenes, will be mentioned. Salts are produced in these reactions, or acetic acid, as in the first example. Allylation of indoles at the 3-position was achieved by using palladium acetate, and bipyridine and allylic acetates as the reactants (Scheme 5) [19]. 

The scheme proposed for the reaction over HFAU was that PA dissociates in phenol (P) and ketene and that o-HAP, which was highly favoured over the para isomer, results partly from an intramolecular rearrangement of PA, partly from acyl group transfer from PA to P whereas p-HAP results from this latter reaction only. In these experiments, the zeolite deactivation was very fast, as a result of coke deposition and zeolite dehydroxylation. Catalyst stability can be considerably improved by operating at lower temperatures and especially by substituting equimolar mixtures of PA and water or P and acetic acid for PA. Much higher HAP yields were obtained by using the P - acetic acid mixture as reactants.[68]... 

The run began with equimolar (0.1 g mol/L) amounts of sodium hydroxide and ethyl acetate as the reactants. Calculate the overall order of the reaction and the value of the reaction rate constant at 298 K, and write the rate expression for the reaction. 

Ethane thiol reacts more readily than the methyl compound, but the main features of the reaction (e.g. the effect of reactant concentration) are similar. The products include some acid (assumed to be peracetic or acetic) as well as sulphur dioxide and acetaldehyde the large sulphur deficit is again ascribed to disulphide formation. In oxygen-rich mixtures all the sulphur is converted to sulphur dioxide. 

Apart from the Grignard reaction and the industrial preparation of alkyl-leads, solutions of alkyl halides as reactants have received relatively little attention. A 6 1 solution of (l)/acetic acid could be used to reclaim rhodium from used catalyst waste (99). The possibility of using aqueous alkyl halides for leaching has been proposed elsewhere 94). Other binary or ternary mixtures containing alkyl halides may well find important applications not yet suspected. 

A route to a, 8-acetylenic aldehydes is based on the fact that triethyl orthoformate in the presence of zinc iodide as catalyst reacts with a terminal acetylene with elimination of ethanol and formation of an acetal, as illustrated for the preparation of phenylpropargyl aldehyde. The reactants are heated neat with the catalyst to about 135°, and ethanol is removed by distillation (about 1 hr.). 

In nickel-catalyzed reactions, the cyclopentane with the electron-withdrawing group in the 3-position (relative to the exo-methylene group) is formed almost exclusively. This is in contrast to the palladium-catalyzed, formal [3-1-2] cycloaddition employing 2-(trimethylsilylme-thyl)prop-3-enyl acetate as precursor, which presumably follows a mechanistically different, ionic pathway. In palladium-catalyzed MCP reactions of that type, the observed selectivity is markedly dependent on the specific reactants. 

H-Mordenite catalyzes the smooth conversion of simple aldehydes and alcohols to form acetals at 30° in the liquid phase. From the examples in Table XXVII, it is apparent that in these heterogeneous catalytic systems, acetal formation is dependent on the structures of both the aldehyde and the alcohol involved. Thus, for a given aldehyde, yields of acetal decreased in the order primary > secondary > tertiary that is, branching at the a-carbon of the alcohol reduced the equilibrium conversion to acetal. In the isobutyraldehyde reactions, an extremely sharp drop in conversion was observed upon changing from isopropanol to fert-butanol as reactant. This observation suggests that, in addition to the increased steric interactions between organic reactants encountered in the tert alcohol system, molecular sieving-type interactions within the narrow mordenite pore system are operative. 

Rhone-Poulenc (now Rhodia) developed up to commercial scale an alternative process based on zeolite Beta [229,230] using acetic anhydride as reactant (Table 2.9). The original process used acetyl chloride in combination with 1.1 equivalents of AICI3 in a chlorinated hydrocarbon solvent, and generated 4.5 kg of aqueous effluent, containing AICI3, HCl, solvent residues and acetic acid, per kg of product. The... 

Initially, a simple Mariotte volumetric method was used to investigate the mass transfer behavior in the catalyst activation. The experimental Mariotte apparatus is represented schematically in Fig. 5 and consisted of a stirred vessel (300 mL) containing acetic acid (200 mL used as reactant and solvent) and the (salen)Co(II) complex to be oxidized. The system was hermetically in contact with pure oxygen at atmospheric pressure. Oxygen consumption was volumetrically determined over time for activation reactions using three different stirring speeds. The use of... 

The imine and iminium functional groupings are, of course, the nitrogen equivalents of carbonyl and O-protonated carbonyl groups, and their reactivity is analogous. The Mannich reaction of pyrrole produces dialkylaminomethyl derivatives, the iminium electrophile being generated in situ from formaldehyde, dialkylamine and acetic acid. There are only a few examples of the reactions of imines themselves with pyrroles the condensation of 1-pyrroline with pyrrole as reactant and solvent is one such example. N-Tosyl-imines react with pyrrole with Cu(OTf>2 as catalyst. ... 

In addition to the regioselective oxidation of the hydroxy groups in virtually every position, a discrimination of the absolute stereochemistry can be achieved by various a- or (3-selective HSDHs. Thus, the stereoinversion of various steroids was achieved by successive oxidation at position 3 with 3a-HSDH and subsequent reduction with 30-HSDH (Fig. 16.2-20)1841. Hydroxy functions in other positions were not modified, and the products at the end of the sequence were essentially pure. Because of the low solubility of the reactants, biphasic systems with ethyl (butyl) acetate as organic solvents were used as reaction media. 

Hydrazine sulfate may replace the hydrate as reactant the sulfuric acid is buffered with sodium acetate, and the resulting sodium sulfate is precipitated by ethanol. The condensation occurs at room temperature or on gentle warming. Ketones require a somewhat longer reaction time than aldehydes. 

The kinetics of the deposition of In20i films have not been investigated by many groups, since most of them concentrate on the physical properties and possible applications. The published results are listed in Table 3-8. In addition, there are only two remarks about decomposition pathways. Maruyama andTabata [111] state that indium acetate needs no oxygen as reactant to form indium oxide, i.e., some of the metal-oxygen bonds are not broken during the deposition. Also, as proposed by Nomura and coworkers [122], the butylindium thiolate decomposes via formation of indium sulfides ... 

This reaction appears to be generally applicable to dienophiles. Acrylonitrile or fumaronitrile react with triethyl phosphite in ethanol to provide the corresponding j -cyanophosphonate esters (44% and 55%, respectively). Ethyl propiolate, triethyl phosphite, and ethanol furnish diethyl 2-carbethoxy-l-ethoxyethylphosphonate, which most probably arises by addition of ethanol to an intermediate species rather than to reactant or product. Reaction of crotonaldehyde with triethyl phosphite in phenol provides the diphenyl acetal of jS-(diethoxyphosphinyl) butyraldehyde (36) (82%). Substitution of ethanol for phenol in this reaction results in a somewhat lower yield (59%) of the corresponding diethyl acetal as well as a 19% yield of the ethyl enol ether of this same aldehyde. 

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