Ketones examples

Note in the ketone example that alkylation of 2-methylcyclohexanone leads to a mixture of products because both possible enolate ions are formed. In general, the major product in such cases occurs by alkylation at the less hindered, more accessible position. Thus, alkylation of 2-niethvTcyclohexanone occurs primarily at C6 (secondary) rather than C2 (tertiary). 

One novel and interesting method of generating a silacarbonyl ylide occurred through the addition of a carbonyl species with a silylene formed under photolytic conditions. Komatsu and co-workers (177) found that photolysis of trisilane (315) in solution with a bulky carbonyl species led initially to the formation of a silacarbonyl ylide followed by a dipolar cycloaddition of an olefinic or carbonyl substrate. Reaction of simple, nonbulky aldehydes led to only moderate yields of cycloadduct, the siladioxolane. One lone ketone example was given, but the cycloadduct from the reaction was prepared in very low yield (Scheme 4.89). 

The Mannich reaction of an aldehyde enol (example Formula C in Figure 12.14) or a ketonic enol (example Formula C in Figure 12.15) often proceeds beyond the hydrochloride of a /l-aminocarbonyl compound or the Mannich base. The reason is that the secondary amine or its hydrochloride, which has previously been incorporated as part of the iminium ion, is relatively easy to eliminate from these two types of product. The elimination product is an a,fi-unsaturated aldehyde (example Formula E in Figure 12.14) or an a,/l-unsaturated ketone (example Formula D in Figure 12.15)—that is, an a,/l-unsaturated carbowyl compound. Figure 13.51 will show how the Mannich reaction of a carboxylated lactonic enol provides access to an a-methylene lactone, that is, an a,/l-unsaturated carboxyl compound. 

Is there a more environmentally friendly reagent available to accomplish the oxidation of alcohols Recently, it has been shown that sodium hypochlorite (NaOCI) in acidic solution is an excellent reagent for the oxidation of secondary alcohols to ketones. Examples are shown in the following equations ... 

Often, performing PCA on a BBL indicates that the S-space is clustered - exemplified by the ketones. More examples can be found in the literature, e.g. the heteroaromatics [22] (10 clusters) and alcohols [36], A second separate PCA for each cluster may be needed to derive good principal properties, design variables, for the clusters. This was not done here in the ketone example, however. 

This method provides an attractive route to unsaturated macrocyclic ketones. Example ... 

Both imidazole-2- and -4-carbaldehydes resist the Cannizzaro, Perkin and benzoin reactions, but the 1-substituted compounds react normally. 1-Substituted 5-nitroimidazole-2-aldehydes condense readily with alkyl aryl ketones. Examples of successful condensations... 

Halt en atoms are well-known initiating spedes (33) and can be readily generated by photolysis of a wide range suitably substituted phenyl ketones. Examples of those which have been reported to be efficient photoinitiators are given below (7). 

Diastereocontrolled reduction of amino ketones represents an attractive route to amino alcohols, many of which are pharmacologically important, and has been exhaustively reviewed. Even in the case of a-amino ketones, examples of high stereoselectivity were rare with conventional metal hydride reagents, and mixtures were common as the amino group became more distant. In contrast, a-triazolyl ketones (64) were reduced with high stereoselectivity by tetraalkylammonium borohydrides to the syn-alcohols (63) in dichloromethane or to the anti isomers (65) when titanium tetrachloride was added (Scheme 10). ... 

In refluxing acetic acid the reagent reduces a-diketones and a-ketols mainly to saturated ketones. Examples ... 

Formaldehyde has long been used as a disinfectant and as a preservative (including embalming fluid) for biological specimens. Its main use is in the production of certain plastics and in binders for plywood. Many important natural substances are aldehydes and ketones. Examples include sex hormones, some vitamins, camphor, and the flavorings extracted from almonds and cinnamon. Aldehydes contain a carbon-oxygen double bond, so they are very reactive compounds. As a result, they are valuable in organic s)mthesis, particularly in the construction of carbon chains. 

Similarly, on triplet excitation, substituted spirocycloalkanones (e.g. 11. 13 ) afford tricyclic ketones. Examples 11 and 13 show that a second conjugated C-C double bond does not necessarily interfere in the usual reaction path. ... 

Examples of name reactions may be found by first considering the nature of the starting material and product. The Wittig reaction, for instance, is given in Section 199 (Alkenes from Aldehydes) and in Section 207 (Alkenes from Ketones). The aldol condensation may be found in the chapters on difunctional compounds in Section 324 (Alcohol, Thiol-Aldehyde) and in Section 330 (Alcohol, Thiol-Ketone). Examples of the synthetically important alkene metathesis reaction are provided primarily in Section 209 (Alkenes from Alkenes). 

Re/tmnaisky reaction. This form of zinc is highly effective for Reformatsky reactions with both o bromo and a chloro esters and with both cyclic and acydic ketones. Reactions proceed in THF at -78 to 0 in 10-30 mmoles. It even effects djastcreospecific Reformatsky leacttans with chiral carbohydiatc ketones. Example ... 

Alcohol, Thiol-Ketone). Examples of the synthetically important alkene metathesis reaction are mostly found in Section 209 (Alkenes from Alkenes). 

Acetylenic ketones. Coke et al. have reported an alternative method to fragmentation of a, -epoxy ketones (2,419-422 3, 293 6, 232-233). The substrate is a )5-halo-a, 8-unsaturated ketone. The reaction involves addition of an alkyllithium to form an alkoxide, which on pyrolysis cleaves to an acetylenic ketone. Examples ... 

Hydrogenation is now the most utilized homogeneous catalytic reaction in process chemistry for the synthesis of enantioenriched material. The scope of highly enantioselective hydrogenation is spectacular. It ranges from olefins and ketones functionalized with ligating substituents to unfunctionalized alkenes and ketones. Examples of the asymmetric... 

Figure 15.18 shows several examples of electrocyclic processes. Since the reactions are always allowed in either a conrotatory or disrotatory manner, the key issue is the control of stereochemistry. Electrocyclic reactions provide a good example of the power of pericyclic reactions in this regard. In all cases, the reaction proceeds as predicted from the various theoretical approaches. The restrictions placed by the orbital analysis on the reaction pathway are nicely demonstrated by examples D and E in Figure 15.18 only the stereochemistry given is found. An instructive example of the fact that it is the number of electrons that controls the process, not the number of atoms or orbitals, is the conrotatory ring closure of the four-electron pentadienyl cation prepared by protonation of a divinyl ketone (example G). 

Encouraged by the enantioselectivity obtained with ketone 44a, a series of N-aryl-substituted ketones (examples shown in Scheme 3.12) were investigated to further understand the N-substituent effect on the epoxidation and to search for more practical ketone catalysts [24e,i]. Ketones such as 44b,c can be readily prepared in four steps in large quantities from inexpensive glucose and anilines [241],... 

Synthesis of important added value organic compounds, in both commodity and fine chemistries (large- and low-scale productions, respectively), namely, via catalytic processes where reactions are accelerated by organometallic catalysts. Examples of the former are polymers, carboxylic acids, aldehydes, alcohols, and ketones. Examples of the latter are compounds with biological/pharmacological activity. 

Thus, the asymmetric catalysis of cyanoethoxycarbonylation, cyanophosphoryla-tion, epoxidation of electron-deficient olefins, Michael reactions of malonates and (3-keto-esters, Strecker reaction of keto-imines, conjugate addition of cyanide to a, (3-unsaturated pyrrole amides, ring opening of meso aziridines with TMSCN and cyanosilylation of ketones (example shown below) have been successfully carried out using these complexes as asymmetric catalysts. 

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