Alkyl esters, substitution

The coumarins (Table VII) react as expected with some suppression of reactivity of the 7-hydroxyl which is attributable to the alkyl-ester substitution. Note that the ester function is not appreciably hydrolyzed (Tables VII, IX) to liberate the 2-hydroxyl under the conditions of the assay. 

R2 = Alkyl, ester, substituted alkyl (eg. CH20Me, CH2OAC)... 

The sodio derivative, which is prepared by mixing alcoholic solutions of the ester and of sodium ethoxide, condenses with alkyl halides to yield mono-alkyl C-substituted products, for example ... 

Detailed mechanistic studies have been carried out on aminolysis of substituted aryl acetates and aryl carbonates. Aryl esters are considerably more reactive than alkyl esters because the phenoxide ions are better leaving groups than alkoxide ions. The tetrahedral intermediate formed in aminolysis can exist in several forms which differ in extent and site of protonation ... 

Vegetable oil-based inks today offered in Germany are mainly for the heatset printing colours cyan, magenta, yellow and to a lesser extent black. The use of fatty acid alkyl esters as high-boiling solvents in offset inks as substitution of mineral oils is also practised [23]. 

Dipolar addition to nitroalkenes provides a useful strategy for synthesis of various heterocycles. The [3+2] reaction of azomethine ylides and alkenes is one of the most useful methods for the preparation of pyrolines. Stereocontrolled synthesis of highly substituted proline esters via [3+2] cycloaddition between IV-methylated azomethine ylides and nitroalkenes has been reported.147 The stereochemistry of 1,3-dipolar cycloaddition of azomethine ylides derived from aromatic aldehydes and L-proline alkyl esters with various nitroalkenes has been reported. Cyclic and acyclic nitroalkenes add to the anti form of the ylide in a highly regioselective manner to give pyrrolizidine derivatives.148... 

The use of alkyl esters in place of ketones resulted in the formation of alkoxypyrimidines 33 which could be converted in high yields, via selective sequential nucleophilic substitutions, into amino dialkoxy and trialkoxy pyrimidines 34 <06EJO3332>. 

Of the 3 possible types of peroxy carbonate esters-dialkyl monoperoxy carbonates, dialkyl diperoxycarbonates and dialkyl peroxydicarbonates-, the latter are by far the least stable group. Several of the 16 alkyl and substituted-alkyl esters prepared decomposed violently or explosively at temperatures only slightly above the temperature of preparation (0-10°C), owing to self-accelerating exothermic decomposition. Several were also explosive on exposure to heat, friction or shock [1], Amines and certain metals cause accelerated decomposition of dialkyl peroxydicarbonates by a true catalytic mechanism [2], Individually indexed compounds are ... 

By modifying the functional groups they can be used,for example, as crosslinkers in high solid or powder coatings and in thermosets. Because of their good miscibility and low melt viscosity, they find applications as melt modifiers and as blend components. Modified hyperbranched polymers, like alkyl chain substituted poiy(ether)s and po-ly(ester)s sometimes exhibit amphiphilic behavior.They can, therefore, be used as carriers for smaller molecules,for example, dyestuff into polypropylene. 

Isowa, Y., Ohmori, M., Ichikawa, T., Mori, K., Nonaka, Y. andKihara, K. (1979) The thermolysin-catalyzed condensation reactions of N-substituted aspartic and glutamic acids with phenylalanine alkyl esters. Tetrahedron Lett., 28, 2611-2612. 

Esterification Reactions. The use of solid acids provides a practical substitute for homogeneous acid catalysts commonly employed to prepare alkyl esters. The use of homogeneous acid catalysts, such as sulfuric acid, and p-toluene- or methane-sulfonic acids, generally results in sulfur contamination of the final product, which upon combustion yield compounds that are known pollutants. 

Neither the anilide of cinnamic acid94 nor the diphenyl substituted acroyl anilide 138 95 yields any product of rearrangement or cyclodimerization. Upon irradiation of 138 in benzene solution in a Pyrex reactor, only the isomeric /9-lactams 139 (2.3%) and 140 (37%), in addition to dihydrocarbostyril 141 (5%), were isolated. The latter is the major product upon irradiation of alkyl substituted acroyl anilides.96 On the other hand, the closely related phenyl cinnamate rearranges regularly to the ortho- and para-positions97 and does not dimerize as the other alkyl esters of cinnamic acid.98... 

Hydrolysis of Alkyl Esters of Inorganic Acids Hydroxy-de-sulfonyloxy-substitution, etc. 

The parent nonclassical thienothiophene (9) is unknown although alkyl- and ester-substituted derivatives (10) and (11) have been generated in solution and found to be highly reactive intermediates. The tetraphenyl derivative (6) of thieno[3,4-c]thiophene, on the other hand, is stable indefinitely in the solid state, although it is destroyed in solution by light and air, but not by light alone. 

The chemistry of phosphate esters is more complicated than that of sulfate esters because it is possible to have one, two, or three alkyl groups substituted for the acidic hydrogens of phosphoric acid ... 

Peptide a-oxo acids 1 (R4=H), a-oxo esters 1 (R4= alkyl or substituted alkyl), and a-oxo-amides 2 (R5=R6=H, alkyl, substituted alkyl, aryl, and/or heteroaryl) are potent reversible inhibitors for cysteine and serine proteases (Scheme 1).[1 9 Their inhibitory potency is the result of their enhanced electrophilic a-carbonyl functional group that can better compete with the substrate in the formation of a tetrahedral adduct with the cysteine or serine residue at the protease active site. In the case of peptide a-oxo esters and a-oxoamides, the extension in PI and beyond gives the inhibitors additional interactions with the protease at the corresponding sites. 

---