Carbonyl compounds intramolecular catalysis

The alkaline hydrolysis of the compounds (118)-(123) in 70% (v/v) dioxane-water at various temperatures has been investigated.101 Intramolecular catalysis by the neighbouring carbonyl group occurs in the alkaline hydrolysis of (118)-(121) and the alkaline hydrolysis of (122) and (123) is rapid owing to their lactone structures. The hydrolyses of C-terminal amides of a-amino acids was dealt with earlier.56 Also, the acid-catalysed cleavage of A-(2-aminophcnyI)phthalamic acid (82) was discussed earlier.72... 

The considerable increase in rate constant associated with this process has been attributed to the induced intramolecular attack in adduct 5 compared to the intermolecular attack of hydroxide ion that is entropically unfavorable [42], The cyclic intermediate 6 readily rearranges into open-chain imine 7. The similarity between this kind of mechanism and enzymatic catalysis has been associated with the use of binding energy to compensate for the entropy cost while coupling the carbonyl compound to the amino group [44] in a way that is similar to the utilization of favorable interaction with non-reacting portion of the substrates by enzymes [45]. 

A major problem in the reaction of a,/3-unsaturated carbonyl compounds and alkenes proves to be the competition between hetero Diels-Alder and ene reactions. Intramolecular cycloadditions of 1,6- and 1,7-dienes with ester and cyano groups at the double bond yield the ene product nearly exclusively, but with alkylidene- and benzylidene-ketoesters and 1,3-diketones the Diels-Alder reaction is preferred under thermal conditions, however under Lewis acid catalysis also ene reactions occur [12]. 

Enamine catalysis using proline or related catalysts has now been applied to both intermolecular and intramolecular nucleophilic addition reactions with a variety of electrophiles. In addition to carbonyl compounds (C = O), these include imines (C = N) in Mannich reactions (List 2000 List et al. 2002 Hayashi et al. 2003a Cordova et al. 2002c ... 

Epoxides can isomerize under the influence of transition metal catalysts. This formal 1,2-hydride shift is a method to prepare unsaturated carbonyl compounds from epoxides (Equation 54) <1998T1361>. This method has been extended as a double epoxide isomerization-intramolecular aldol condensation (Equation 55) <1996JOC7656, 1998TL3107>. m-Epoxides are isomerized to /ra r-epoxides under ruthenium catalysis <2003TL3143>. 

The great majority of intramolecular cyclopropanation reactions of unsaturated a-diazo-carbonyl compounds have been achieved with copper catalysts, especially with copper powder or copper bronze, copper(II) sulfate, and bis(acetylacetonato)copper(II). Homogeneous catalysis by bis(salicylaldimato)copper(II) or copper(I) halide/trialkyl phosphite complexes has repeatedly been reported to be superior to heterogeneous catalysis by other copper(I) and cop-per(II) salts, e.g. formation of and 2. ... 

Biaryl structures are found in a wide range of important compounds, including natural products and organic functional materials [8,80,81]. One of the most common and useful methods for preparing biaryls is the palladium-catalyzed coupling of aryl halides with arylmetals (Scheme 1, mechanism A). On the other hand, aryl halides have been known to couple directly with aromatic compounds as formal nucleophiles under palladium catalysis. While the intramolecular cases are particularly effective, certain functionalized aromatic compounds such as phenols and aromatic carbonyl compounds, as well as... 

Pascal R (2003) Catalysis through induced intramolecularity what can be learned by mimicking enzymes with carbonyl compounds that covalently bind substrates Eur J Org Chem 2003 1813-1824... 

The a-alkylation of carbonyl compounds is a key carbon-carbon bond forming reaction in organic chemistry. Despite the widespread apphcations of this method, a general asymmetric intramolecular a-alkylation via enamine catalysis has proven to be extremely challenging because of catalyst alkylation, or racemization of products in the reaction. List and coworkers developed an intramolecular a-alkylation of aldehydes by using (S)-a-methylproline (15) as the catalyst [10]. To eliminate the influence of the by-product HX, a stoichiometric amount of NEts was added. A diversity of chiral cyclopentanes and pyrrolidines 17, or cyclopropanes 19, could be obtained in high yields and ees (Scheme 36.5). 

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