Reactivity of carbonyl group

Strong through-space interactions are possible in medium rings. Such interactions have been discovered in certain alkaloids like cryptopine and protopine, which are characterized by atypical properties of their functional groups like low basicity of amino groups and low carbonyl reactivity of carbonyl groups. 

It also explains the reactivity of carbonyl groups since the Ji bond is weaker than the o bond and is more likely to be involved in reactions. 

The relatively slow transmetallations of alkyl halides means that generally only alkyl iodides can be used as precursors for cyclisation onto any but the least reactive of carbonyl groups. The resulting alkyllithiums will cyclise onto nitriles, amides, esters, and, in some cases ketones. Direct addition to the C=0 group is slower with r-BuLi than with n-BuLi, but so is the transmetallation, and ft-BuLi is generally the better choice except with ketones. 

Like other, 8-dicarbonyl compounds, the substituted keto amides (X)—(XV) are very reactive and represent the key intermediates in a complex set of side reactions [95]. A considerable amount of research has been devoted to the elucidation of the reactions of these compounds under polymerization conditions [118—120,124,125,127,128, 130,131, 134—143]. With respect to the high reactivity of carbonyl groups and the adjacent —CH2— or i CH- groups, the structures like (X)—(XV) are unstable at elevated temperatures and even less stable in the presence of a strong base. Bukac and Sebenda [137] showed that keto amides with one hydrogen atom at the nitrogen decompose very easily in the presence of base into isocyanate which takes part in many subsequent reactions, scheme (45). The most important consequence of side reactions is the fact that water is present even if the anionic polymerization is started under... 

There might seem to be some confusion as to the oxygen atom with which the proton is associated. From, our discussion of polarizability (p. 28) and the reactivity of carbonyl groups (p. 156), we should expect the proton to be found on the keto-oxygen atom ... 

Pratap, R., Gupta, R.C., and Anand, N., Comparative reactivity of carbonyl groups in 6P-methyl-ciT-bicyclo[4.3.0]nona-3,7-dione, Indian J. Chem., Sect. B. Tl. 731, 1983. 

The sequence of reactions nicely points out the relative reactivity of carbonyl groups at positions 3, 11 and 17. Reaction of the triketone 29-2 with a controlled amount of pyrrolidine leads to the formation of the enamine from the most reactive ketone, that at C3 (30-1) (Scheme 5.30). Treatment of this intermediate with methylmagnesium bromide leads to exclusive addition to C17. Although the ketone at Cn is virtually inert to addition reactions, it is subject to reduction. Reaction of 30-2 with lithium aluminum hydride thus leads to the corresponding j8-hydroxy derivative. The enamine is then removed by acid hydrolysis (30-4). Reaction of the newly formed alcohol with /i-toluenesulfonyl... 

Density-LUMO Maps Reactivities of Carbonyl Groups... 

The different reactivity of carbonyl groups in keto aldehyde substrates has been exploited for the synthesis of phenanthrols, naphthols, and their heteroatom-containing analogues via a catalyst-free intramolecular formal diazo carbon insertion of iV-tosylhydrazones into keto C-C bonds (Scheme 197). ... 

Carbonyls. The title compound is widely used as an oxophilic Lewis acid, efficiently increasing the reactivity of carbonyl groups toward the additions of many nucleophiles. a-Dicarbonyls are particularly effective substrates for this kind of activation. A catalytic amount of In(OTf)3 combined with a multidentate chiral ligand allows nucleophiles, such as allylstannanes (eq 23), electron-rich... 

Relative Reactivities of Carbonyl Groups Aldehydes Are More Reactive than Ketones... 

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