Bases. ketones

There also exists an acidregioselective condensation of the aldol type, namely the Mannich reaction (B. Reichert, 1959 H. Hellmann, 1960 see also p. 291f.). The condensation of secondary amines with aldehydes yields Immonium salts, which react with ketones to give 3-amino ketones (=Mannich bases). Ketones with two enolizable CHj-groupings may form 1,5-diamino-3-pentanones, but monosubstitution products can always be obtained in high yield. Unsymmetrical ketones react preferentially at the most highly substituted carbon atom. Sterical hindrance can reverse this regioselectivity. Thermal elimination of amines leads to the a,)3-unsaturated ketone. Another efficient pathway to vinyl ketones starts with the addition of terminal alkynes to immonium salts. On mercury(ll) catalyzed hydration the product is converted to the Mannich base (H. Smith, 1964). 

They are attacked by fuming sulfuric acid, some amines, strong bases, ketones, esters, dimethylformamide, dimethylsulfoxide. 

Scheme 8.12 gives some examples of these palladium-based ketone syntheses. 

Essentially concurrently, the C2-symmetric ketone catalysts 8-10 were reported . In regard to the enantioselectivity, the TADDOL (o ,Q ,Q , Q -tetraaryl-l,3- oxolane-4,5-dimethanol)-derived ketone 10 performs better than the binaphthalene-based ketone 6, but not as well as the fructose-modified ketone 7, whereas 10 is more resistant than 7 in regard to oxidative degradation. ... 

Sulphuric acid (concentrated). Widely used in desiccators. Suitable for drying bromine, saturated hydrocarbons, alkyl and aryl halides. Also suitable for drying the following gases hydrogen, nitrogen, carbon dioxide, carbon monoxide, chlorine, methane and paraffins. Unsuitable for alcohols, bases, ketones or phenols. Also available with an indicator (a cobalt salt, blue when dry and pink when wet) under the name Sicacide (from Merck) for desiccators. 

Unfortunately, it has been assumed in many of the studies on the irradiation of polymer-doped or polymer-based ketones that cyclization processes are the fate of only a small fraction of the BRs. Although this may... 

Hull and Conant in 1927 showed that weak organic bases (ketones and aldehydes) will form salts with perchloric acid in nonaqueous solvents. This results from the ability of perchlonc aad in nonaqueous systems to protonate these weak bases. These early investigators called such a system a superacid. Some authorities believe that any protic acid that is stronger than sulfunc aad (100%) should be typed as a superaad. Based upon this criterion, fluorosulfuric arid and trifluoro-methanesulfonic acid, among others, are so classified. Acidic oxides (silica and silica-aluminai have been used as solid acid catalysts for many years. Within the last few years, solid acid systems of considerably greater strength have been developed and can he classified as solid superacids. 

Reductions of cyclic enediones by NaBH4 in the presence of CeCl3 are controlled by accessibility for complexation by the Lewis acid and therefore more regioselective than those conducted without complexation.239 This combination of reagents in MeOH has been used for the selective reduction of a decalin-based ketone from the more hindered, equatorial face of the molecule.240 Use of 1.4 equiv. of NaBH4 and 1.1 equiv. of CeCl3 at high dilution (0.005 m) and low temperature (—95 °C) led to a 95 5 ratio of the axial to equatorial alcohol (compared with a 20 80 ratio in the absence of cerium). 

In the presence of a base, ketones with a hydrogens react to form a haloke tones. 

FETFE (fluo-roelastomer with TFE additives) Alcohols, aldehydes, chlorinated organics, paraffins, concentrated mineral acids, and mild bases Ketones and ethers Typical color black Temperature range -23 to 240°C. Firm compression. Density 1.85 0.85... 

In the presence of strong bases, ketones and aldehydes act as weak proton acids. A proton on the a carbon atom is abstracted to form a resonance-stabilized enolate ion with the negative charge spread over a carbon atom and an oxygen atom. Reprotonation can occur either on the a carbon (returning to the keto form) or on the oxygen atom, giving a vinyl alcohol, the enol form. 

The pyrolysis liquids consist mainly of tar, light oil, and liquor. The tar contains 16-25% olefins, 62-80% aromatics, and 3-14.5% paraffins and naphthenes, and the remainder is organic compounds that have been identified as acids, bases, ketones, and... 

An interesting variation of this rearrangement appears when the diynol 272 is treated with base". Ketone 274 is obtained, apparently by way of the intermediate allenol 273. 

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