Tetrolic acid, methyl ester

Tetrolic acid has been prepared by treatment of acetoacetic ester with phosphorus pentachloride followed by dehydrochlorination of the reaction products by the base-catalyzed isomerization of 3-butynoic acid and by the treatment of 4,4-dibromo-3-methyl-2-pyrazolin-5-one with alkali followed by acidification. ... 

The esters of acetylenic acids, with the exception of a,/3-unsatiU ated acids, can be converted to hydrazides. Ethyl stearolate and ethyl undecynoate readily give hydrazides, the latter in 80% yield. Esters of a,/3-acetylenic acids react with hydrazine to form pyrazolones for example, ethyl tetrolate gives 3-methyl-5-pyrazolone. ... 

A soln. of crotyl bromide (mixture with 3-bromo-l-butene) in abs. ether added slowly to Mg in ether at such a rate as to keep the mixture under reflux, stirring continued 1 hr. at room temp., the ether removed with dry Ng, the residue dissolved in tetrahydrofuran, a soln. of (+)-8-methyl-frans-hydrindan-4-ol-l-one in the same solvent added dropwise, stirred 2 hrs. at room temp., then allowed to stand overnight, the product treated with osmium tetroxide, the resulting osmic acid ester isolated by filtration and refluxed 3.5 hrs. with Na-sulfite in water-ethanol tetrol (Y 88%) dissolved in dioxane, and shaken 75 min. with Pb-tetraacetate under Ng dihydroxyaldehyde (Y 74.5%). H. H. Inhoffen, H. Burkhardt, and G. Quinkert, B. 92, 1564 (1959). 

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