Oxiranes opening with acetate/acetic acid

An oxirane formed by the direct epoxidation, which usually occurs from the sterically least hindered side of the molecule, can be converted into its stereoisomer by a reaction sequence which involves the diaxial opening (in acetic acid at 100° for 2 hr) of the epoxide to a diol mo noacetate. Subsequent mesylation followed by treatment with base gives the inverted oxirane, as shown for the sequence (69) (70) (71) (72). ... 

Similarly, the epoxide (72), on reaction with BH3/UBH4, acetic acid or BC13 gave the tetrahydrothiophene derivatives (74a-c), presumably via the intermediate (73), unlike the analogous cyclohexyl and N-alkylpiperidyl compounds, in which the oxirane opened to give only the expected alcohols (equation 21) (75CPB2701). 

Oxiranes can be opened stereo- and regiospecifically under mild conditions with alcohols, thiols, amines, and acetic acid, with simultaneous activation of the nucleophilic and electrophilic centers on an alumina surface.Diols have been obtained on silica gel in the presence of water " and adsorbed FeCls. On an ion-exchange resin, the opening of oxirane isomers to diols and the separation of the latter, ethanolysis, the reaction with phenol,and catalytic ammonolysis have been described. Hydrolysis and methanolysis catalyzed by Nafion-H, a perfluorinated resinsulfonic acid have been reported. ... 

Pyridazines have been prepared from a variety of other heterocyclic systems and in most cases these transformations were specific. The 3(S), 4(5) 36, a constituent of the antibiotic antitumor luzopeptin A, was prepared in a multistep synthesis from malonaldehyde dimethyl acetal in 32% overall yield. In the last step a highly regiospecific nucleophilic ring opening of the glycidic acid (oxirane derivative) took place (89JOC3260). In another example, c75,frani-l,3-cycloundecadiene was transformed in five steps in low yield into 59. In the last step the epoxide 58 was treated with excess of LDA (89TL4649). 

C2-homologizati on of sugars with, 264-265 Acetamide, JV-bromo- (AcNHBr, NBA) bromohydrination with, 275-276, 287 Acetaminophen (= paracetamol), 301 Acetate, piperidinium cat. for aldol add., 82 —, sodium a-epimerization of ketones, 277 opening of oxiranes, 282 Acetic acid, anhydride (AcfO) protection with. See Protection Pummerer rearr. with, 51, 265 —, esters (See also Protection of hydroxy groups) C-H acidity, 10 1-methylethenyi ester pr., 174 transenolization, 58 —, bromo-, esters pr., 179 a2-synthon, 19, 65, 309 d2-synthon, 19, 301 —, chloro-, esters pr., 179 hydantoins from, 308 —, cyano-, esters pr., 177 pyrrolines from, 298 —, (dialkoxyphosphinyl)-, esters pr 188 Wittig-Horner olefinations, 267, 282 —, diazo-, ethyl ester pr, 176, 178 cyclopropanes from, 74—75 —, dichloro- deblocking of pixyl ethers, 342 —, hydroxy-, esters pr., 176 —, hydroxyphenyl-, (S)- (l-mandelic acid) ... 

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