Acetone, addition reactions

As with other reversible nucleophilic addition reactions the equilibria for aldol additions are less favorable for ketones than for aldehydes For example only 2% of the aldol addition product of acetone is present at equilibrium... 

These effects can be attributed mainly to the inductive nature of the chlorine atoms, which reduces the electron density at position 4 and increases polarization of the 3,4-double bond. The dual reactivity of the chloropteridines has been further confirmed by the preparation of new adducts and substitution products. The addition reaction competes successfully, in a preparative sense, with the substitution reaction, if the latter is slowed down by a low temperature and a non-polar solvent. Compounds (12) and (13) react with dry ammonia in benzene at 5 °C to yield the 3,4-adducts (IS), which were shown by IR spectroscopy to contain little or none of the corresponding substitution product. The adducts decompose slowly in air and almost instantaneously in water or ethanol to give the original chloropteridine and ammonia. Certain other amines behave similarly, forming adducts which can be stored for a few days at -20 °C. Treatment of (12) and (13) in acetone with hydrogen sulfide or toluene-a-thiol gives adducts of the same type. 

To this there is added dropwise with continued cooling and stirring a solution of ethyl chlorocarbonate (0.1 mol). After approximately 10 minutes, the acylating mixture is cooled to about -5°C and then is slowly added to a stirred ice-cold mixture of 6-aminopenicillanic acid 0.1 mol), 3% sodium bicarbonate solution (0.1 mol) and acetone. This reaction mixture is allowed to attain room temperature, stirred for an additional thirty minutes at this temperature and then is extracted with ether. 

Optically pure (S)-benzyl methyl sulfoxide 139 can be converted to the corresponding a-lithio-derivative, which upon reaction with acetone gave a diastereomeric mixture (15 1) of the /S-hydroxysulfoxide 140. This addition reaction gave preferentially the product in which the configuration of the original carbanion is maintained. By this reaction, an optically active epoxy compound 142 was prepared from the cyclohexanone adduct 141181. Johnson and Schroeck188,189 succeeded in obtaining optically active styrene oxide by recrystallization of the condensation product of (+ )-(S)-n-butyl methyl sulfoxide 143 with benzaldehyde. 

Highly stabilized phosphorus ylides are prepared from acetylenic esters, a carbon-based nucleophile, and triphenylphosphine in aqueous media.40 In acetone-water (2 1) solvent, the reaction proceeds via the conjugate addition of triphenylphosphine to dialkyl acetylenedicarboxy-lates the resulting vinyl triphenylphosphonium salts undergo Michael addition reaction with a carbon-nucleophile to give the corresponding highly stabilized phosphorus ylides. 

Isocyanides and dialkyl acetylenedicarboxylates in the presence of 2,4-dihydro-3//-pyrazol-3-ones 344 in acetone at ambient temperature undergo a smooth 1 1 1 addition reaction to produce highly functionalized 7-oxo-17/,7H-pyrazolo[l,2-tf]pyrazole derivatives 345 in 69-81% yields (Equation 47) <2005T3963>. 

The relative proportions of unsaturated carbohydrate, sensitizer (usually acetone), and solvent may have a decided effect upon a photochemical addition reaction, as at least three competing processes (cycloaddition, radical addition, and energy transfer) are possible. The irradiation of 1 in the presence of 2-propanol and acetone provides an illustration (see Scheme 4). When a small proportion of sensitizer... 

A suspension of a cell line (usually T lymphocyte lines such as HG, HUT-78, or CEM) infected with HIV is spotted on microscope slides, air dried, and fixed in acetone. Addition of uninfected cells to the suspension provides a means for detecting nonspecific reactions in the same smear. Typical localized fluorescence of infected cells is seen after reaction with positive sera. Little or no fluorescence is seen with negative sera. 

Intermolecular free-radical addition reactions almost always proceed by chain mechanisms. Here light photoexcites acetone, and O then abstracts H- from the a-position of another molecule of acetone to complete the initiation. 

A highly efficient asymmetric induction was also observed in the addition of the lithium salt of (+)-(5)-34 to acetone (313). The addition product 297 (optical purity ca. 80%) was then oxidized to the corresponding sulfone 298, whose absolute configuration was established as R by means of chemical correlations. The formation of sulfone 298 with the absolute configuration R at carbon proves that, unlike methylation, the addition reaction takes place with retention of configuration. It is worthy of note that the optically active... 

The addition reaction of tetracyanoethylene and ethyl vinyl ether in acetone gives 94% of the 2 + 2 adduct and 6% of an adduct having the composition tetracyanoethylene + ethyl vinyl ether + acetone. If the 2 + 2 adduct is kept in contact with acetone for several days, it is completely converted to the minor product. Suggest a structure for this product, and indicate its mode of formation (a) in the initial reaction and (b) on standing in acetone. 

In the low-temperature fluorination of benzofuran (39, Y = O) and 1-acetylindole (39. Y = NAc), addition reactions are observed as well as vicinal fluoro trifluoromethoxy adducts 40A and 40B, vicinal difluoridcs 41 are formed.63 Trichloromethiazide is converted into the 5-fluoro derivative 42 in tetrahydrofuran/hydrogen fluoride at 0 C (in dichloromethanc/acetone 42 is accompanied by two nonfluorinated products).64... 

Discrete dimers of the head-to-head type have been found in the structures of the Ag+ complex of (145)570 and the Na+ complex of (145)571 respectively. The complexes were recrystallized from carbon tetrachloride. In both complexes each metal is five-coordinated in the cavity provided by one anion, and there is an additional reaction with the second anion [through an Ag+-phenyl interaction or an Na+-carboxylate oxygen atom (Figure 32a)]. When the Na+ complex was crystallized from a solvent of medium polarity, acetone, the head-to-head dimer was recovered.571 In contrast, recrystallization from a polar medium, methanol, gave a monomeric complex in which one methanol of solvation was also present.572 In all of these complexes an intramolecular head-to-tail hydrogen bond was present to hold the ligand in its pseudo-macrocyclic conformation. 

In a number of cases, an addition reaction of OH radicals to olefins has been required to explain several of the major products. Although OH abstracting from olefins and H02 reactions with olefins can also explain some of the products, only the addition reaction is uniquely satisfactory. Thus, it is difficult to see how CH3 radicals, required to explain the presence of methane, can be obtained from C2H3 radicals which would be formed in an abstraction reaction of OH with C2H4. Similarly, while acetone and propylene can be plausibly formed if H02 attack is mainly responsible for the removal of 2-butene, it is not easy to see how the large quantities of methane are produced. It is not possible, of course,... 

In the dehydrogenation of isobutyric acid, the by-products in addition to CO and C02 are propylene and acetone. Two reaction mechanisms were proposed (340, 341) and the latter is shown in Scheme 9 (340). The formation of methacrylic acid and acetone involves a common intermediate The El elimination of a proton from I yields the methacrylic acid while a nucleophilic SN1 attack of oxide ion produces C02 and acetone (344). On the other hand. 

Addition reactions of carbon radicals to C—O and C—N multiple bonds are much less-favored than additions to C—C bonds because of the higher ir-bond strengths of the carbon-heteroatom multiple bonds. This reduction in exothermicity (additions to carbonyls can even be endothermic) often reduces the rate below the useful level for bimolecular additions. Thus, acetonitrile and acetone are useful solvents because they are not subject to rapid radical additions. However, entropically favored cyclizations to C—N and C—O bonds are very useful, as are fragmentations (see Chapter 4.2, this volume). 

Cu(II) and Sn(II) Bisoxazolinc Complexes. Evans has prepared and studied a family of Cu(II) complexes prepared from bisoxazoline ligands [8]. Utilizing these complexes a number of different addition reactions can be successfully conducted on pyruvate, benzyloxyacetalde-hyde, and glyoxylates. Whereas the focus of the work in the context of aldol addition reactions has been on the use of silyl ketene acetals (vide infra), the addition of ketone-derived enoxy silanes 8a-b with methyl pyruvate has been examined (Eq. 8B2.1). The additions of 8a-b proceed in the presence of 10 mol % Cu(II) catalyst at -78°C in CH2Cl2, affording adducts of acetophenone 9a and acetone 9b with 99% and 93% ee, respectively. 

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