With carbonyl group esters

Most stable enol double bond conjugated with carbonyl group ester carbonyl stabilized by resonance... 

Many other organometaUic compounds also react with carbonyl groups. Lithium alkyls and aryls add to the ester carbonyl group to give either an alcohol or an olefin. Lithium dimethyl cuprate has been used to prepare ketones from esters (41). Tebbe s reagent, Cp2TiCH2AlCl(CH2)2, where Cp = clyclopentadienyl, and other metal carbene complexes can convert the C=0 of esters to C=CR2 (42,43). 

We have recently investigated X-ray structure of 3-methoxycarbonyl-[l,4,2] diazaphospholo[4,5-a]pyridine as first example of molecular structure determination for [l,4,2]diazaphosphole ring [84], The ester substituent lies strictly in the molecular plane with carbonyl group in the trans orientation with the formal C=P bond. Endocyclic P-N and P-C bonds are averaged between respective single and double bond lengths. 

Peroxyl radicals are known to react with olefins by an addition reaction (see Chapter 2). The same reaction was proposed for compounds with carbonyl groups (ketones, esters [77]). 

Sodium borohydride is selective it usually does not react with carbonyl groups that are less reactive than ketones and aldehydes. For example, carboxylic acids and esters are unreactive toward borohydride reduction. Thus, sodium borohydride can reduce a ketone or an aldehyde in the presence of an acid or an ester. 

The rearrangement of acetals of 2-haloalkyl aryl ketones is a well-documented process yielding esters of 2-arylalkanoic acids by 1,2-aryl shift (equation 7). The mechanism of this rearrangement is reminiscent of other semipinacol rearrangements. Loss of the halogen (usually assisted by Lewis acid), yields a carbocation (4), which then undergoes a 1,2-aryl shift with carbonyl group formation. 

With an acceptor-substituted alkene moiety tethered to the molecule, the intermediate silyl enol ether may undergo an intramolecular [2-I-2] cycloaddition.The silyl-assisted addition of hydrogen halides to cyclopropanes is not restricted to ketones with carbonyl groups as activating function or iodide as nucleophile. Esters and other acid derivatives underwent similar reactions when treated with iodotrimethylsilane alone or in the presence of an additional catalyst such as mercury(II) or zinc(II) chloride.Subsequent treatment of the y-iodo ester with potassium carbonate in tetrahydrofuran gave the respective y-butyrolactones in good yield. 

Simple n bonds of this type are also found in molecules with carbonyl groups — aldehydes, ketones, carboxylic acids and esters (Structures 5.1). 

Aspirin is a phenyl ester. Phenyl esters arc considerably more susceptible to hydrolysis than ordinary esters arc. for two reasons Delocalization of a lone electron pair from the phenol oxygen into the carbonyl group (ester resonance, sec Section 20-1) is diminished, because this lone pair is also in resonance with the benzene ring. The result is a greater 8 on the carbonyl carbon, which facilitates nucleophilic attack. The... 

Intramolecular Wittig reactions can be used for the preparation of cyclic alkenes. The formation of the phosphonium ylide must be compatible with other functionality in the molecule and thus stabilized ylides are used most commonly. Wittig reactions with carbonyl groups other than aldehydes or ketones, such as carboxylic esters, are known. For example, a route to the indole or penem ring systems uses a carboxylic amide or a thioester respectively as the intramolecular electrophile (2.77). 

This reaction was first reported by Kishner in 1911. It is the preparation of cyclopropane derivatives by decomposition of pyrazolines formed from hydrazine and a,p-unsaturated ketones or aldehydes. Therefore, it is known as the Kishner reaction, Kishner decomposition, or Kishner method. In addition, this reaction has been modified to prepare pyrazoline intermediates from diazomethane and unsaturated carbonyl compounds, such as maleic and fumaric esters, resulting in an ester group in the trans position. However, when maleic anhydride or maleimide is used, the corresponding pyrazoline is formed with carbonyl groups in the cis configuration. It has been found that the stability of pyrazolines varies considerably, decomposing to cyclopropanes at different rates. Moreover, the transformation of pyrazolines into cyclopropanes can be catalyzed by a trace amount of mercuric ion. ... 

The Homer-Emmons modification uses a phosphonate-stabilized carbanion in a Wittig reaction. This reagent is an anion that is more nucleophilic than the usual Wittig ylide. The byproduct (R0)2P02 is water-soluble and easily separated from the product. These phosphonate-stabilized carbanions are compatible with carbonyl groups (especially esters) in the reagent. 

Similarly polyimides with carbonyl groups in the main and side chains, and with alkanoxide groups in the main chain have been prepared. Polyimides have also been prepared without catalysts from di-isocyanates and dianhydrides in conjunction with their diakyl esters in aprotic solvents. ... 

An approach taken to overcome these deficiencies is the use of the so-called sacrificial spacers [29]. In this method the intermediate species used during the pre-polymerization of the MIP to link the monomers and the template is chosen so that it is eliminated—or in other words sacrificed—during the removal of the template. This way not only is the template attached to the monomer, the chances of steric influences of the residual moe-ities during the future rebindings with the target species are also avoided. Instances of the common sacrificial intermediate species are spacers with carbonyl groups [59-70] or the less frequent instances of salicylate (2-hydroxybenzoate) [60,71], dimethyl silyl group of silyl ethers [72] and silyl esters [73]. 

After Zn(OAc)2 transmetalation Pd-catalyzed cross-coupling with the bromothiophene 18 provides the substituted thiophene 19 in 75% yield. The presence of carbonyl groups (ester or amide) precludes the use of TiCLr, Bids, or InCls as additives. However, by employing 3% PbCl2 a smooth insertion reaction with several functionalized iodides, such as 20 and 21, or with the bromide 22 (Scheme 1) [10] occurs, providing the derived functionalized aluminum reagents 23-25 in good yields. 

The substrate itself also activates the reagent 4. Alkoxy group at a-position of ketone will form a chelate intermediate that activates the f)is(iodozindo)methane to react with carbonyl group of ketone. Such substrates with 4 undergo methylenation in the absence of any additive. As shown in Scheme 8.15, a substrate that has a-benzyloxyketone and simple ketone groups in the same molecule can be converted into the chemoselective methylenated product. In the methylenation reaction, activations of bis(iodozindo)methane (4) have been done with titanium salt, a-alkoxy group of ketone, THT, or ionic liquid. This means that the readivity of 4 can be tuned to perform a seledive methylenation. In Scheme 8.16, a keto alkanal and a keto ester were examined for the chemoseledive methylenation [18,23,27]. 

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