Tosylethyl Esters and Related Base-Labile Groups

In 1%8 Miller and Stirling showed that the 2-tosylethyl ester function (abbreviated TSE) underwent easy base-catalysed elimination in the presence of 1 M sodium hydroxide or sodium carbonate (but not sodium hydrogen carbonate) in aqueous dioxane at room temperature to give p-toluenesulfinate anion, ethylene, and a carboxylate. Thus, this ester function complements the methylsul-fonylmethyl function (see section 6.4) derived from methylthiomethyl esters in its base-sensitivity. Electron withdrawing groups (e.g., p-nitro) on the aryl ring increase base lability — a feature that has been exploited for the protection of the 2 hydroxyl function in oligoribonucleotide synthesis. [Pg.437]

Silyl esters are seldom used because they are too labile to mild acid or base to survive even simple manipulation. Their inclusion here is intended to underline their lability in comparison to the corresponding silyl ethers. On rare occasions the lability of silyl esters is an asset that can be exploited in very sensitive substrates. Silyl esters protect acids against reduction with hydroborating agents. [Pg.440]

Silyl esters are generally prepared from the carboxylic acid and the corresponding silyl chloride or silyl triflate in the presence of base (pyridine, triethylamine. [Pg.443]

4 Esterification and Alkylation Reactions Employing Isoureas. Mathias. L. J. Synthesis, 1979, 561. [Pg.445]

5 The Chemistry of Carboxylic Acid Derivatives. Supplement B. Patai. S, Ed. Wiley New York, 1979. [Pg.445]

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