Malonaldehydic acid diethyl acetal

The ozonolysis reaction, followed by reductive workup with sulfur dioxide, as described in Part A of the present procedure, illustrates a general method which has been developed for the preparation of acetals. Application of the procedure is illustrated by conversion of the following olefins in alcoholic solution to the corresponding acetals (1) l-chloro-4-(o-nitrophenyl)-2-butene to o-nitrophenylacetaldehyde dimethyl acetal in 84% yield (2) l,4-dibromo-2-butene tobromoacetaldehyde dimethyl acetal in 67% yield (3) 3-butenoic acid to malonaldehydic acid diethyl acetal ethyl ester in 61% yield (4) cyclopentadiene to malonaldehyde bis(diethyl acetal) in 48% yield and (5)... 

All four isomeric selenolopyridines which can be derived from benzoselenophene (423— 426 Scheme 123) have been described. Ethyl 3-hydroxyselenolo[2,3-fe]pyridine-2-carboxy-late (429) has been prepared as shown in Scheme 124 (73BSF704). Treatment of ethyl 2-chloropyridine-3-carboxylate with methaneselenol yields (427). Nucleophilic displacement of bromine in bromoacetic acid with subsequent loss of methyl bromide yields (428), which after esterification is cyclized under Dieckmann conditions to give (429). The parent compound (423 colorless oil with b.p. 92 °C/1 mmHg) is prepared either by cyclization of compound (430) and subsequent decarboxylation of the intermediate acid (equation 57) or by reduction of 2-nitroselenophene and subsequent condensation of the amino compound with malonaldehyde bis(diethyl acetal) in the presence of zinc chloride (equation 58) (76BSF883). Selenolo[3,2-6]pyridine (426 b.p. 127-129°C/10 mmHg m.p. 35.5-37.0°C) has been obtained in an analogous manner. 

Concentrated hydrochloric acid (20 mL) is added to a vigorously stirred solution of 100 mL (0.34 mole) of 1,1,3,3-tetraethoxypropane [malonaldehyde bis-(diethyl acetal)] in 100 mL of distilled water. To this is added, dropwise, 17.5 mL (0.34 mole) of bromine. ( Caution. Use a fume hood.) The coloration of the bromine disappears immediately if the dropping rate is sufficiently slow. No increase in temperature is observed. 

Chromans. - 2,4-Diethoxychromans (78) (mainly cis) represent a new type of chroman and have been prepared in high yield from a phenol (but not a deactivated phenol) and malonaldehyde bis(diethyl acetal) in the presence of SnCU they are converted into the benzopyrylium salts (79), in excellent yield, by treatment with perchloric acid. A Wittig-Horner reaction of the chiral phosphoryl ( S)-sulphoxide (81) and the ketone (80) gave the chiral sulphoxide (82), which was cyclized by aqueous alkali to a mixture which contained 22% diastereoisomeric excess of (25 )-chroman (i )-sulphoxide. This was converted, in three steps, into the aldehyde (83), which is a useful synthon for a-tocopherol. ... 

Tetraethoxypropane (malonaldehyde tetraethylacetal) (XII-41) and diethyl malonate in acetic anhydride give diethyl 3-ethoxyallylidenemalonate (Xn-42), which cyclizes ii polyphosphoric acid or formic acid to the pyrone XII-43. Reaction of W42 with ammonia w henzylamine forms 3-aminoallylidenemalonates (XII-44 R = H, GHjCgHs), which are cyclized to the ethyl a-pyridone-3carhoxylates (XII-4S) in alcoholic sodinm ethoxide or piperidine. ... 

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