Dialkyl ketones, molecular

The molecular structure of (ebi)TiCl2 has been determined by X-ray diffraction.1660 A,A-(ebthi)TiX2 derivatives have been used to effect the catalytic hydrosilylation of a wide variety of dialkyl ketones.1661... 

Togo and coworkers have found that alkyl aryl ketones and dialkyl ketones could be converted into the corresponding a-tosyloxyketones in generally low yields by the reaction with mCPBA and p-toluenesulfonic acid monohydrate in the presence of a catalytic amount of molecular iodine in a mixture of acetonitrile and 2,2,2-trifluoroethanol (method A, Scheme 4.5) [23]. The same conversion of ketones into the corresponding a-tosyloxyketones could be smoothly carried out by the reaction with mCPBA and TSOH H2O in the presence of catalytic amounts of iodine and fert-butylbenzene in a mixture of acetonitrile and 2,2,2-trifluoroethanol (method B). In these reactions, p-iodotoluene 8 (method A) and 4-fcrr-butyl-l-iodobenzene 9 (method B) are formed at first and are then converted into the corresponding [hydroxy(tosyloxy)iodo]arenes, ArI(OH)OTs,... 

Complexes of lithium aluminium hydride with l,4 3,6-dianhydro- and 1,3 4,6-di-O-benzylidene-D-mannitol, each of which contains a two-fold axis of symmetry, have been used to achieve asymmetric reductions of some alkyl aryl and dialkyl ketones e.g. methyl or ethyl phenyl ketone and 3,3-dimethylbutan-2-one). All reductions with lithium l,4 3,6-dianhydro-D-mannitolatodihydridoaluminate(iii), using a 2 1 molecular ratio of ketone to reducing agent, gave the 5-enantiomer of the secondary alcohol preferentially (selectivity 1.1—5.3 %), whereas those of alkyl aryl ketones and dialkyl ketones gave more of the 5- and R-alcohols, respectively, when lithium l,3 4,6-di-0-benzylidene-D-mannitolatodihydridoaluminate(iii) was used. 

The intensities of aldehydic carbonyl absorptions have not been widely studied, but Cross and Rolfe [56] have given a few values for the extinction coefficients of aldehydes which can be compared with those of the corresponding ketones. Propional and heptanal (1735 cm and 1736 cm ) have a molecular extinction coefficient of 130 and 148 as compared with about 180 for dialkyl ketones. Crotonaldehyde has a value of 234 and benzaldehyde of 324. This latter value is comparable with the value of 310 given by acetophenone. Parallel data are given by Renema [180]. From the limited data available, therefore, it would appear that the intensities of the carbonyl bands of aldehydes will vary with structural features in much the same way as do those of ketones. 

The current work indicates that sulfided platinum catalysts are, in general, more active and selective than Pt, Pd, or sulfided Pd catalysts for reductive alkylation of primary amines with ketones. The choice of the catalyst preparation parameters, especially the support, plays a major role in determining the performance of the catalyst. Diamines, especially of lower molecular weight, tend to react with ketones even at room temperature to form heterocycles such as imidazolidine, diazepanes, and pyrimidines. Hence, a continuous reactor configuration that minimizes the contact between the amine and the ketone, along with a highly active catalyst is desired to obtain the dialkylated product. In general, sulfided Pt appears to be more suited for the reductive alkylation of ethylenediamine while unsulfided Pd or Pt may also be used if 1,3-diaminopropane is the amine. 

Derivatives of diazoethene have been invoked as highly unstable intermediates in a series of Wittig reactions. Gilbert s group added ketones to dimethyl diazomethyl-phosphonate (2.241) in the presence of potassium eA butoxide in THF at - 78 °C. In addition to potassium dimethyl phosphate and molecular nitrogen, dialkylated ethynes (2.246) were isolated. Scheme (2-95) shows the intermediates that are likely for this reaction C-Alkylation (2.242) is followed by the formation of a 1,2-oxaphosphetane (2.243). Elimination of dimethyl phosphate gives the diazoethene (2.244), from which N2 is eliminated to form the carbene 2.245. The alkyne is formed by the usual 1,2-shift of one of the alkyl groups. The carbene 2.245 can... 

This reaction was first reported by Hantzsch in 1890. It is the preparation of 2,5-dialkyl or 2,4,5-trialkylpyrrole derivatives from the condensation of of-halo-ketones, )0-ketoesters and ammonia or amines. Therefore, it is often known as the Hantzsch pyrrole synthesis or simply the Hantzsch synthesis. During this synthesis, ammonia or amine reacts quickly with y0-keto esters to form enamine esters or 3-amino crotonates that cyclize with of-halo-ketones to form pyrrole derivatives upon heating, and the regioselectivity strongly depends on the substituents on the starting materials. Thus, this reaction can directly start from 3-amino crotonates or enamines of 0-keto esters. Further extension of this reaction from aromatic amines results in the formation of indole derivatives, or carbazole derivatives if cyclized with a-halo-cyclohexanones. The synthesized pyrroles have wide application in medicinal chemistry, conducting polymers, molecular optics, sensors,etc. 

Stelling (1928) found an absorption band in formaldehyde and acetone bisulfite addition compounds at 4992.0 A similar to that in sulfonic acids at 4992.2 and differing from that of metal alkyl (4996.0) and dialkyl sulfites (4997.7). He concluded from this that the sulfonic acid structure must be present. Raman spectral examinations of several aldehyde and ketone bisulfites by Caughlan and Tartar (1941) revealed the presence of a carbon-sulfur bond, possibly a carbon-hydroxyl bond, but no carbon doubly bonded to oxygen. This thus aided in discrediting both the tripartite molecule and the sulfurous acid ester structures. Sundman (1949) believes that formation of a stable monomolecular complex of boric acid and glucose bisulfite would be impossible if Schroeter s tripartite molecular structure were correct. His examinations of this complex led him to believe that its structure could be represented only by ... 

The world s most popular method of PVC polymerization is the suspension method. Around 80% of PVC is produced this way. The difference in this method is that it uses initiators soluble in the monomer. They are dialkyl and diacyl peroxides, ketone peroxides, peroxo-dicarbonates, peroxo-ketals, alkyl peresters or azo compoimds. Seldom is the role of emulsifiers played by alkalies or buffers in order to improve the plasticizer adsorption in PVC. In this process, in order to obtain proper porosity and particle granulation, so-called suspension stabilizers are used, which are derivatives of meth-ylhydroxypropyl cellulose, karboxymethyl cellulose and poly(vinyl alcohols). PVC obtained this way is of high purity. Its molecular mass depends on the temperature of polymerization. Other parameters depend on the interfacial tension at the water-monomer interface. 

Huang, Liang et al. developed a direct Cul-catalyzed synthesis of polysubsti-tuted pyrroles from dialkyl ethylenedicarboxylates and -enamino ketones or esters in moderate to good yields with molecular oxygen (1 atm) (Scheme 8.5). Variation of N-substituents, aromatic ring, alkyl, and ester could be obtained smoothly. In this procedure, molecular oxygen was used as the oxidant and the C(sp )-H bond of the -enamino ketones was cleaved [15]. 

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