Pyridines mixed, with ketones

In alcohols, water is found to be partially displaced, and it is possible to have the water/salt ratio in a saturated solution considerably less than that in the hydrated solid in equilibrium with it (4> 10). As with pyridine, an alcohol in a heterogeneous system will sometimes displace water well enough to make the difference between extraction and nonextraction of a metal-ion value (29). Another way in which the differences between strong water-competitors such as alcohol and weaker competitors such as the ketones and ethers are manifested is when liquid such as CC14, with no solvent power of its own for the salt, is mixed with the oxygenated solvent. With thorium nitrate as the test salt, it is seen (Fig. 2) that, whereas addition... 

The mode of addition of hydrogenphosphonates to fluorinated ketones can also be complex. The addition of dialkyl, diphenyl or bis(trimethylsilyl) hydrogenphosphonates to methyl trifluoromethyl ketones occurs in the expected manner, but this contrasts with the behaviour of aryl perfluoralkyl ketones in the presence of triethylamine at room temperature, when the products, obtained even under such mild conditions, are phosphate esters (reaction 6), a situation which represents lack of stability of the hydroxyphospho-nate rather than novelty of the reaction under identical conditions, the corresponding alkyl aryl ketones fail to react. The same reaction with mixed-halogen ketones is still more involved, and the nature of the products depends on the reaction conditions if these are of a mild nature, and with catalysis by triethylamine or pyridine (depending on the particular ketone), the product is the expected (hydroxyalkyl)phosphonate 177, whereas with... 

Cr3+ can also be integrated into the structures of layered double hydroxides. A mixed oxide, prepared by calcination of ZnCr-LDH-CCh, was used in combination with t-BuOOH for the ketonization of alkyl and of benzyl pyridines and for the oxidation of benzyl amines to give Schiff bases (67,68). In contrast to MgAl-LDHs, for example, these materials display hardly any basicity so that base-catalyzed side reactions such as aldol condensations are avoided. 

Phenyl ketones (201), readily prepared from compounds with cholanic acid or lanosterol side chains, are degraded in alkaline solution by molecular oxygen, giving bisnorcholanic acids (202). Decarboxylation with lead tetra-acetate in benzene, with a little pyridine, completed the degradation to a pregnane derivative, giving the mixed 20-acetates (203) with overall yields in the range 30—40% for the two steps.177... 

Preparation of secondary (or tertiary) carbinols from pyridines and an aldehyde (or a ketone) in the presence of magnesium or aluminum and mercuric chloride is known in pyridine chemistry as the Emmert reaction. 7 70 For example, dimethyl-2-pyridylcarbinol is obtained in this way from pyridine and acetone. When a mixture of pyridine and acetone is subjected to an electrolytic reduction in dilute sulfuric acid at lead electrodes, a mixture of two main products results, namely, 2-(2-hydroxy-2-propyl)-3-piperideine and 4-(2-hydroxy-2-propyl)piperidine. Analogous compounds are obtained with the use of methyl ethyl ketone as the reactant. The mixed electrolytic reduction of 2-methylpyridine and acetone affords 2-(2-hydroxy-2-propyl)-6-methyl-3-piper ideine (74) and 2-methyl-4-(2-hydroxy-2-propyl)-piperidine.71... 

An earlier application of 1,4-conjugate additions employing azaallyllithium reagents formed from ketone dimethylhydrazones is Kelly s hydrazone version of the classical Knoevenagel route to substituted pyridine derivatives.71 In this chemistry, a mixed cuprate derived from a dimethylhydrazone lithio anion and copper thiophenoxide was first allowed to react with an a,p-unsaturated ketone. The product enolate can then be acylated or protonated to yield either a diketo hydrazone or a keto hydrazone. Addition of... 

The in situ generation of methyl vinyl thioketone in refluxing pyridine provided each of the four possible mixed Diels-Alder products derived from 4w and 2w methyl vinyl thioketone participation in [4 + 2] cycloadditions with methyl vinyl ketone [Eq. (I)].3... 

The use of chromium(VI) reagents as oxidants is limited by their inherent toxicity, the need to prepare them in various complex forms (with acetic acid or pyridine), and complicated work-up procedures. Chromium trioxide (Cr03) immobilized on pre-moistened alumina affords efficient oxidation of benzyl alcohols to carbonyl compounds by simple mixing. Remarkably, neither the over-oxidation to carboxylic acids nor the usual formation of tar, a typical occurrence in many CrOj oxidations, is observed [108]. The reagent system is also used for the preparation of acyclic a-nitro ketones by the oxidation of nitroalkanols under solvent-free conditions [109]... 

OL-Iodo ketones, a-lodo ketones are usually prepared by reaction of enol acetates with NIS. A new method involves reaction of an alkene with silver chromate and iodine in the presence of pyridine. The actual reagent is presumably a mixed anhydride of hypoiodous acid and chromic acid. Dichloromethane is the most useful solvent. ... 

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