Ethyl hydrogen tartrate

Preparation 197.—Ethyl Hydrogen Tartrate [.Monoethyl ester of 2 3-butandiolrdiacid]. 

According to Guerin798 ethyl hydrogen tartrate is formed smoothly on distillation of the acid with anhydrous ethanol the product crystallizes on addition of water. 

At least eighteen phenylethylamines have been examined by x-ray crystallography. Among these are phenylethylamine hydrochloride (3 ), ephedrine hydrochloride (31), ephedrine monohydrogen phosphate monohydrate (32), ephedrine dihydrogen phosphate (33), dopamine hydrochloride (34), 5-hydroxydopamine hydrochloride (35), 6-hydroxydopamine hydrochloride (36), epinephrine hydrogen tartrate (37), norepinephrine hydrochloride (38), isoproterenol sulfate (39), 2,4,5-trimethoxyamphetamine hydrochloride (40), 4-ethyl-2,5-dimethoxyamphetamine (41), mescaline hydrobromide (42), and mescaline hydrochloride (43). 

The original synthesis of diethyl teUnride by Wohler was carried out by treating potassium telluride with ethyl sulfate. The preparation of potassium telluride was rather inconvenient and involved the reduction of elemental tellurium by heating the element at red heat with potassium-hydrogen D-tartrate. An early report of Natta demonstrated that the treatment of aluminium telluride by alcohols or ethers at 250-300 °C is also a promising route to diorganyl tellurides. 

When tartaric acid is heated with alcohol in the presence of hydrogen chloride, two hydrogen atoms are replaced by two ethyl groups, and diethyl tartrate is formed. This reaction shows that the acid contains two carboxyl groups. When diethyl tartrate is heated with acetic anhydride, two acetyl groups are introduced. The ester, therefore, contains two alcoholic hydroxyl groups. 

Cyclopropyl thien-2-yl ketone (34), available commercially, was subjected to a Grignard reaction with 21 to yield a carbinol (31) in excellent yield. Bromotrimeth-ylsilane-mediated opening of the cyclopropyl ring led to the 4-bromo derivative 32. Condensation with ethyl i -(-)-pipeildme-3-carboxylate (16) was conducted in isopropyl acetate as a solvent with anhydrous lithium carbonate as the base. The transformation was cleaner and did not provide any of the diene (26) arising from elimination of hydrogen bromide. The alkylation of the nipecotate residue could also be directly effected with a mixture of the tartrate salt of 16, lithium carbonate, and isopropyl acetate. Compound 33 was readily isolated as the hydrochloride isopropyl acetate was superior to all other solvents used in this reaction. Since it is not itself prone to hydrolysis, it is preferable to ethyl acetate. Moreover, it appears to crystallize hydrochlorides much better. 

ADP Ammonium di-hydrogen Phosphate, KAP Pottasium Acid Phtha-late, TAP = Thallium Acid Phosphate, EDDT Ethyl di-amide D-Tartrate (C6H14N2O6), PET Penta Erythritol, RAP Rubidium Acid Phthalate. 

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