Esterification alkene derivatives

Electrophilic alkenes have been appended to imidazolium-type ILs for use in the Diels-Alder cycloaddition, 1,4-addition, Heck and Stetter reactions.Electrophilic alkenes containing Wang-type linkers were alkylated to imidazole followed by ion exchange and esterification giving the desired TSIL. Diels-Alder cycloaddition was carried out with 2,3-dimethylbutadiene and cyclopentadiene to give corresponding adducts. After washing with ether, transesterification resulted in cyclohexene derivatives. Scheme 29. 

Another interesting HMF-derived compound is levulinic acid formed together with formic acid by solid acid catalysis. A one-pot cascade route from c.g. inulin seems feasible. Manzer et al. [37] give examples in which an esterification step with an alkene is coupled as well. The... 

Pentanediol [(R,/ )-28] has been used for the formation of chiral acetals and as a precursor for chiral alkenes (Sections D.1.5.1. and 1.6.1.5.). The original procedure for the resolution of the phenylboronic acid derivative with brucine39 was impractical, but recently a kinetic resolution by lipase-catalyzed esterification and hydrolysis has been developed40. In addition, a good method for catalytic reduction of 1,3-diketones with Raney nickel modified with sodium bromide and tartaric acid (for a procedure, see Section D.2,3.1.) allowed the production for commercial purposes41. Similarly, sterically more hindered and less water-soluble 2,6-dimethyl-3,5-heptanediol (29) has been introduced for the same purpose. It is obtained in the same way from the diketone and separated from the meio-compound by simple recrystallization42. 

As with other diazoalkanes, diazomethane reacts with alkenes to form cyclopropane derivatives (sec. 13.9.C.i).272 Reaction with aromatic derivatives leads to ring expansion to cycloheptatriene derivatives.223 Both of these reactions (addition to an alkene or arene insertion) involve generation of an intermediate carbene and addition to a jt bond they will be discussed below. Many of the reactions of diazomethane tend to be ionic in nature and are, therefore, set aside from the other diazoalkane chemistry in this section. One of the commonest uses of diazomethane itself is esterification of small quantities of acids, especially acids that are precious for one reason or another. The reaction is quantitative and gives good yields of a single product, as in Tadano s conversion of 338 to the methyl ester of 339224 in a synthesis of (-)-verrucarol. 

The use of a substoichiometric amount (20 mol%) of an external chiral source was first demonstrated in the asymmetric olefination of a 4-substituted cyclohexanone [103] by using a chiral phase-transfer catalyst 186 derived from cinchonine here, a combination of the chiral phase-transfer catalyst and rubidium hydroxide as a base was essential in generating the dissymmetric alkene 187 with 57% ee after a re-esterification step (Scheme 7.30). Though the problem of low turnover still has to be solved, this result provided an informative concept for the... 

In studies directed towards the synthesis of pseurotin A, the unsaturated acetal 3 has been used as a common starting material to prepare two different C-2-branched intermediates. In one route, 3 was 0-benzylated, the aldehyde im-masked with hydrochloric acid and oxidized to its carboxylic acid derivative. Esterification, dihydroxylation of the alkene then dimethylsulfoxide-thionyl chloride oxidation, addition of ethylmagnesium chloride and removal of the isopropylidene group gave compounds 4. In an alternative route, 3 was first epoxidized then treated sequentially with hydroxide, benzyl bromide-base and hydrochloric acid to give compounds 5. ... 

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