Succinic acid 2,3-disubstituted

In the hydroxycyclopropanation of alkenes, esters may be more reactive than N,N-dialkylcarboxamides, as is illustrated by the exclusive formation of the disubstituted cyclopropanol 75 from the succinic acid monoester monoamide 73 (Scheme 11.21) [91]. However, the reactivities of both ester- as well as amide-carbonyl groups can be significantly influenced by the steric bulk around them [81,91]. Thus, in intermolecular competitions for reaction with the titanacydopropane intermediate derived from an alkylmagnesium halide and titanium tetraisopropoxide or methyltitanium triisoprop-oxide, between N,N-dibenzylformamide (48) and tert-butyl acetate (76) as well as between N,N-dibenzylacetamide (78) and tert-butyl acetate (76), the amide won in both cases and only the corresponding cyclopropylamines 77 and 79, respectively, were obtained (Scheme 11.21) [62,119]. 

This procedure illustrates a process which should be general for many a,a-disubstituted succinic acids. It is more convenient than those previously employed because the reaction sequence is carried out in one step. 

Just as with 1,2-diCO compounds, we can buy the 1,4-relationship rather than make it. Any supplier s catalogue will reveal a wide variety of such compounds we shall mention only a few. There are simple disubstituted butanes such as the diol 71, the diamine 72, the dihalides 73 and succinic acid 74. 

For the preparation of long chain alkanes from fatty acids it is useful to extract the electrolyte contin-ously with a high-boiling nonpolar solvent, e.g. 2-methylheptane. Cyclopropanecarboxylic acids in some cases have been dimerized, e.g. or (15) in other cases the radical is further oxidized to a carbocation which then undergoes ring opening and solvoiysis to allylic compounds. Specifically substituted 1,2-diphenyiethanes have been prepared from phenylacetic acids (Table 2, entries 22 and 23). A variety of 2,3-disubstituted succinic acids and their derivatives have become accessible from malonic... 

Disubstituted acids Dimethyl-succinic acids—Diethyl-succinic acids—Tetramethyl-succinic acid—Methyl-acrylic acid—Ethyl-crotonic acid. [Campholytic acid—Campho-thetic acid—Allocampholytic acid—Laurolene.].38-42... 

If disubstituted maleic anhydride is used in this reaction, even with boiling in toluene solution for 46 h, the process does not go past the stage of formation of the corresponding derivative of succinic acid-3-[(3-methylquinoxalin-2-yl)methyl]-3,4-diphenyldihydrofuran-2,5-dione 55 (Fig. 3.4), which is isolated with a yield of 90 % (Cheeseman and Tuck 1965a). 

Starch adipate, a cross-bonded starch for food use, is made by reaction with adipic anhydride, which is formed from adipic acid in the presence of excess acetic anhydride. It is also a labile ester, and after hydrolysis with alkali, followed by acidification, is extracted with ethyl acetate and silylated. Gas chromatographic analysis is performed on a capillary column of fused silica coated with dimethyl siloxane, film thickness 5 pm. Pimelic acid is the internal standard. The method cannot differentiate between mono- and disubstitution. Alkyl succinate substitution can be determined using the same procedure as for adipate. 

A general method has been worked out which allows the preparation of a number of butanediols-1,4 substituted in the 2,3-position (16,43). Starting materials are a-halo-genated (usually a-bromo) esters of alkanoic acids which can be condensed to 2,3-disubstituted succinate esters they are readily reduced with LiAlHij to the 2,3-disubsti-stituted butanediols-1,4 which are acetylated and then pyrolyzed at about 600°C. Dehydration of the butanediols-1,4 with KHSOi, on the other hand gives only 3,4-substituted tetrahydrofuran. 

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