Carbonyl-containing compounds

The mam synthetic application of Grignard reagents is their reaction with certain carbonyl containing compounds to produce alcohols Carbon-carbon bond formation is rapid and exothermic when a Grignard reagent reacts with an aldehyde or ketone... 

We 11 Start by discussing m more detail a class of compounds already familiar to us alcohols Alcohols were introduced m Chapter 4 and have appeared regularly since then With this chapter we extend our knowledge of alcohols particularly with respect to their relationship to carbonyl containing compounds In the course of studying alco hols we shall also look at some relatives Diols are alcohols m which two hydroxyl groups (—OH) are present thiols are compounds that contain an —SH group Phenols, compounds of the type ArOH share many properties m common with alcohols but are sufficiently different from them to warrant separate discussion m Chapter 24... 

This cleavage reaction is more often seen in structural analysis than in synthesis The substitution pattern around a dou ble bond is revealed by identifying the carbonyl containing compounds that make up the product Hydrolysis of the ozonide intermediate in the presence of zinc (reductive workup) permits aide hyde products to be isolated without further oxidation... 

What structural features are responsible for the reactivity order of carboxylic acid derivatives Like the other carbonyl containing compounds that we ve studied they all have a planar arrangement of bonds to the carbonyl group Thus all are about the same in offering relatively unhindered access to the approach of a nucleophile They differ m the degree to which the atom attached to the carbonyl group can stabilize the carbonyl group by electron donation... 

Performing the titration to a potentiometric end point, rather than to a colored end point, has been shown to be the more accurate method. Since other carbonyl containing compounds also react to form the oxime and release hydrochloric acid, this test is not specific for benzaldehyde. 

All carbonyl-containing compounds have intense IR absorptions in the range 1650 to 1850 cm-1. As shown in Table 21.3, the exact position of the absorption provides information about the specific kind of carbonyl group. For comparison, the IR absorptions of aldehydes, ketones, and carboxylic acids are included in the table, along with values for carboxylic acid derivatives. 

There have been two general approaches to the direct asymmetric epoxidation of carbonyl-containing compounds (Scheme 1.2) ylide-mediated epoxidation for the construction of aryl and vinyl epoxides, and a-halo enolate epoxidation (Darzens reaction) for the construction of epoxy esters, acids, amides, and sulfones. 

The synthesis of nitrogen containing heterocyclic systems by photocylo-addition processes is virtually limited to examples involving [ 2 + 2] cycloaddition of imines, nitriles, and azo compounds. Successful additions are few in number and the requirements for success uncertain. The reactions do not proceed with the facility with which carbonyl containing compounds undergo photocycloaddition to alkenes to give oxetans, and various explanations have been advanced to account for this observed lack of reactivity.226... 

The observations recorded in Tables I and II reveal that no product was isolated when reaction of a sugar was attempted with the following classes of carbonyl-containing compound monocarbonyl compounds a-ketonic acids or esters y-carbonyl compounds and /3-carbonyl compounds yielding a high percentage of enolic form. A possible course (A) has been formulated for the reaction which occurs with appropriate substances this takes into consideration the mobility of the enol and the reactivity of the glyco-... 

As with pyridazines, phthalazines, the other benzopyridazines, were also prepared most frequently through the condensation of hydrazines with carbonyl-containing compounds, typically phthalate derivatives. Recently, Napoletano and co-workers demonstrated the condensation of hydroxylactone 189 and hydrazine to afford phthalazones 190. After POCI3 chlorination, advanced intermediates for a novel series of PDE4 inhibitor I, phthalazines 191 were prepared <00BMC2235>. 

Table 5.2 Kinetic data for the reaction of EtsSi radicals with a variety of carbonyl-containing compounds [49]...

Analyses of the chloroform-soluble extracts of the subbituminous coal by Fourier transform infrared spectroscopy (FTIR) showed the presence of a sharp carbonyl absorption peak (1800-1650 cm ) in the extracts from the parent coal and in those obtained at yields less than about 10% wt dmmf. The peak, which is attributed to ketones and carboxylates, disappeared at higher conversions (16). Whitehurst and co-workers (12) established that carbonyl- containing compounds, such as esters and carboxylates, can cleave under thermal treatment to produce CO, CO2 and phenols. They concluded that the evolution of these gases during coal liquefaction could originate from the decomposition of similar oxygen functionalities in the coal. 

Mukiayama aldol reactions between silyl enol ethers and various carbonyl containing compounds is yet another reaction whose stereochemical outcome can be influenced by the presence of bis(oxazoline)-metal complexes. Evans has carried out a great deal of the work in this area. In 1996, Evans and coworkers reported the copper(II)- and zinc(II)-py-box (la-c) catalyzed aldol condensation between benzyloxyacetaldehyde 146 and the trimethylsilyl enol ether [(l-ferf-butylthio)vinyl]oxy trimethylsilane I47. b82,85 Complete conversion to aldol adduct 148 was achieved with enantiomeric excesses up to 96% [using copper(II) triflate]. The use of zinc as the coordination metal led to consistently lower selectivities and longer reaction times, as shown in Table 9.25 (Eig. 9.46). 

As with ciimolines, phthalazines were also prepared most frequently through condensations of hydrazine derivatives and carbonyl-containing compounds. For example, Monneret and co-workers reported the condensation of dialdehyde 148 with hydrazine to produce phthalazine derivative 149, an advanced intermediate in the preparation of anticancer analogs of etoposide <99T12805>. 

Quenching of Singlets of Carbonyl-Containing Compounds, a. Acetone. Recent reports have shown that singlet complications are not restricted to hydrocarbons for example, the photodecomposition of 1,4-dichlorobutane (52) to free radicals is sensitized by the (n, n) singlet state of acetone.216 Besides the observations that 52 quenches acetone fluorescence and that... 

On-the-fly molecular dynamics have been employed in order to simulate the photochemistry of carbonyl-containing compounds. The on-the-fly mechanism implemented in the MNDO program is the velocity-Verlet algorithm. Here an additional aspect of the usage of a computational cheap semiempirical method is visible. In order to provide realistic relative yields of different photochemical reactions, a large enough sample of trajectories is needed. For these systems, a substantial amount of trajectories (around 100) has been calculated for a relatively long timescale (up to 100 ps). 

Aldose reductase (ALR2 EC 1.1.1.21) is an 36 kDa enzyme that catalyzes the reduction of a wide range of carbonyl-containing compounds to their corresponding alcohols. It is a member of an extensive aldo-keto oxidoreductase enzyme family, a collection of structurally similar proteins expressed in both animals and plants. Most members of the enzyme family possess similarities in molecular mass, pH optimum, coenzyme dependence, and demonstrate overlapping specificity for many substrates and inhibitors. 

Several reagents for derivatization of carbonyl groups are also available. Dansylhydrazine reacts with carbonyl groups in the presence of trichloroacetic acid, yielding highly fluorescent dansylhydrazones that exhibit, however, limited stability. In addition, fluorescent hydrazones can be produced from carbonyl-containing compounds after their reaction with 4-hydrazino-2-oxa-l,3-diazole or... 

Figure 9.13—Effect of resonance on carbonyl-containing compounds. Representation of the delocalisation of valence electrons in mesomeric forms of organic compounds. In1 C NMR, the signal corresponding to a carbonyl in an ester is at 165 ppm, whereas it is at 205 ppm for a ketone.

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