Tetracyanoethylene acetals

Tetracyanoethylene (500 mg TCNE dissolved in 100 ml of acetonitrile or ethylene acetate) reacts with aromatic compounds, forming colored zones on a slightly yellow background. In some cases, heating to 100°C is necessary to complete the reaction. 

The EtsSiH/tetracyanoethylene combination reduces acetals and ketals to the corresponding ethers but the yields are mixed.500 The full reduction of benz-aldehyde acetals to the toluene derivatives is realized by the initial reduction with Et3SiH/SnBr2-AcBr followed by Bu3SnH/AIBN (azobis(isobutyronitrile)) or LiAlH4.479 The overall yields are excellent. 

Table I records the results obtained in the preparation of 30 cycloaddition products from the acridizinium cation. As was demonstrated by Fields, Regan, and Dignan, even preparative experiments done at different temperatures and in different solvents are adequate to prove the inverse electron demand character of the reaction. Nucleophilic alkenes, like ketene diethyl acetal, reacted in minutes at room temperature while the strongly electrophilic alkene, tetracyanoethylene, failed to react under any conditions.

Next to iodine there is also another class of neutral Lewis acids known. Tetracyanoethylene, dicyanoketene acetals and derivatives can catalyse reaction due to their tt-Lewis acid properties. They promoted the alcoholysis of epoxides [238], tetrahydropyranylation of alcohols [239], monothioacetahzation of acetals [240], and carbon-carbon bond formation of acetals [241,242] and imines [243] with silylated carbon nucleophiles. 

Urea (4.0 g., 0.067 mole) is dissolved in 50 ml. of distilled ethylene glycol (Note 1) contained in a 125-ml. Erlenmeyer flask. Finely divided recrystallized tetracyanoethylene 2 (25.6 g., 0.20 mole) is added, and the flask is heated on a steam bath at 70-75° with frequent stirring by hand with a thermometer until solution is complete (about 15 minutes). The resultant brownish-yellow solution is then cooled in ice water, and the precipitated dieyanoketene ethylene acetal is collected on a Buchner funnel. The acetal is first washed with two 25-ml. portions of cold ethylene glycol and then washed thoroughly with cold water to remove the ethylene glycol. The dieyanoketene ethylene acetal, which may be dried in air or in a vacuum desiccator, is obtained in (he form of large slightly pink needles, m.p. 115-116.5° (Note 2) yield 21 -23 g. (77-85%). 

Coupling, of diazotized Ji-aminoaceto-phenone with quinone, 34, 1 of diazotized 3,5-dichloro-2-aminoben-zoic acid to give 4,4, 6,6 -tetra-chlorodiphenic acid, 31, 96 of dibromomalononitrile to tetracyanoethylene, 39, 65 of diphenyldichloromethane to tetra-phenylethylene, 31,104 Creased flask, 37, 55 Creosol, 33,17 Crotonaldehyde, 33, 15 34, 29 diethyl acetal, 32, 5 reaction with ethynylmagnesium bromide, 39, 57... 

The experiments with reversible poisoning of alumina by small amounts of bases like ammonia, pyridine or piperidine revealed [8,137,142,145, 146] relatively small decreases of dehydration activity, in contrast to isomerisation activity which was fully supressed. It was concluded that the dehydration requires only moderately strong acidic sites on which weak bases are not adsorbed, and that, therefore, Lewis-type sites do not play an important role with alumina. However, pyridine stops the dehydration of tert-butanol on silica—alumina [8]. Later, poisoning experiments with acetic acid [143] and tetracyanoethylene [8] have shown the importance of basic sites for ether formation, but, surprisingly, the formation of olefins was unaffected. 

The function of the urea is not known. Addition of urea to a solution of tetracyanoethylene in ethanol produces a brilliant purple color as hydrogen eyanide is evolved, the color fades, and the solution becomes nearly colorless. Pyridine and zinc acetate also catalyze the reaction, but urea is the best eatalyst found. 

Heterocycles Acetylacetone. N-Aminophthalimide. Boron trichloride. Dichloro-formoxime. Oicyanodiamide. Dicyclohexylcarbodiimide. Dietboxymethyl acetate. Diethyl oxalate. Diketene. Dimethylformaniide diethylacetal. Diphenyldiazomethene. Ethyl ethoxy-methylenecyanoacetate. Formaldehyde. Formamide. Formamidine acetate. Formic acid. Glyoxal. Hydrazine. Hydrazoic acid. Hydroxylamine. Hydroxylamine-O-sulfonic acid. Methyl vinyl ketone. o-Phenylenediamine. Phenylhydrazine. Phosphorus pentasullide. Piperidine. Folyphosphoric acid. Potassium diazomethanedisulfonate. Sodium ethoxide. Sodium nitrite. Sodium thiocyanate. Tetracyanoethylene. Thiosemicarbozide. Thiourea. Triethyl orthoformate. Tris-formaminomethane. Trityl perchlorate. Urea. Vinyl triphenyl-phosphonium bromide. 

Dehydrooenation 1,4-Benzoquinone. Chloranil. o-Chloranil. Copper chromite. Copper-Chromium oxide. Diethyl azodicarboxylate. 2,3-Dichloro-3,6-dicyano-I,4-benzoquinone. DIphenylpIcrylhydrazyl, N-Lithioethylenediamlne. Mercuric acetate. Nickel catalyst. Oleic add, Palladium. Perbenmic acid. Potassium l-butoxide. Pyrldinium hydrobromide per-bramlda, Balinlum. Selenium dioxide. Sodium borohydride. Sulfdr (sm 1,2-Naphthalic anhydridli preparation). Tetracyanoethylene. Thionyl chloride. Trityl perchlorate. 

The purple charge-transfer complex of indole with tetracyanoethylene decomposes in neutral or basic media to the 3-substituted indole (164), whereas under acidic conditions the 2-(tricyanovinyl)-isoraer is formed. The cyclo-adducts of l-benzyl-3-vinylindole to tetracyanoethylene and maleic anhydride are the cyclobutane (165) and the tetrahydrocarbazole (166), respectivelyThe reaction of 9-methyl-l,2,3,4-tetrahydrocarbazole (167) with dimethyl acetylenedicarboxylate in aqueous acetic acid yields a mixture of the bridged compounds (168) and (169). The photo-adduct (170) of methyl acrylate to 1-benzoylindole rearranges to the benzazepine (171) in hot xylene... 

Nitrile, azo, and nitroso groups, and even the oxygen molecule, take part in such reactions, and acetylenic triple bonds in particular confer reactivity as philodiene. As for dienes, so for philodienes the reactivity depends on the constitution. Activating groups particularly favor addition. The most reactive components include <%,/ -unsaturated carbonyl compounds such as acrolein, acrylic acid, maleic acid and its anhydride, acetylenedicarboxylic acid, p-benzo-quinone and cinnamaldehyde, as well as saturated nitriles and <%,/ -unsaturated nitro compounds. Tetracyanoethylene also reacts with dienes.41,42 Conjugation of the double bond to an active group is not absolutely essential for a philodiene, for dienes add under certain conditions also to philodienes with isolated double bonds examples of the latter type are vinyl esters and vinyl-acetic acid. Ketenes do not undergo the Diels-Alder reaction with dienes, but instead yield cyclobutanone derivatives 43,44... 

Cyanohydrins and ethers. Tetracyanoethylene has been introduced as a new catalyst for the carbonyl derivatization. KCN-Znl2 is used to achieve syn-selective derivatization of /3-hydroxy ketones. Exchange of one alkoxy group of an acetal in a TMSOTf-catalyzed process is subject to remote asymmetric induction. The monoadduct of benzoquinones can be reduced by Sml2 to give p-hydroxybenzonitriies. ... 

Tetrachlorobenzyne, 523, 524 Tetrachloroethylene, 413 Tetracyanoethylene, 271, 567-568 Tetracyclines, 109 Tetracyclone, 489, 490, 548, 577 9,11-Tetradecadien-l-yl acetate, 546 E-7-Tetradecene-l-ol acetate, 12 1,2,4,5-Tetraenes, 146 Tetraethylammonium bromide, 568-569 Tctraethylammonium chloride, 480 Tetraethylammonium cyanide, 569... 

Ergocalciferyl acetate forms an adduct, probably of Diels-Alder type, with tetracyanoethylene. The stability of the adduct to air, and also to t.l.c. or g.l.c., suggests its possible adoption for estimation of calciferol in animal tissues. ... 

The Diels-Alder adduct between levopimaric acid and maleic anhydride, maleopimaric anhydride (Fig. 4.8) and the corresponding diacid are certainly the most important derivatives of this family mainly because of their applications in various domains. Levopimaric acid has also been used in the preparation of other adducts with a wide variety of dienophiles such as fumaric acid, acrylonitrile, acrylic acid, vinyl acetate and tetracyanoethylene [5]. 

Tetracyanoethylene added in small portions to a soln. of 156 g. vitamin A acetate in chloroform with stirring, whidi is continued 2.5 hrs. at room temp., and the resulting crude intermediate refluxed 3 hrs. in cyclohexane at ca. 80° [9,10,10-... 

In the presence of tetracyanoethylene, 0x0 compounds can be obtained directly by ozonization of ethylene derivatives. In most cases no side reactions occur.— E A soln. of camphene and tetracyanoethylene in ethyl acetate ozonized at — 70° until a light blue color appears camphenilone (Y 72-80%) and tetracyanoethylene epoxide (Y 81%). F. e. s. R. Griegee and P. Gunther, B. 96, 1564 (1963). 

Tetracyanobutanal acetal (216) (readily obtained from tetracyanoethylene, ethyl vinyl ether, and ethanol) has been reported to be converted into 2-aminopyridine derivative (219) in the presence of pyridine. On the basis of several experiments, the proposed mechanism involves the Michael reaction of (216) via (217) with diene (218), generated by the elimination of hydrogen cyanide and ethanol from (216), followed by double intramolecular nucleophilic additions to the cyano groups. ... 

Salicylamide 0-acetic acid 280 Stearyl alcohol 8307 Tetracyanoethylene 9783... 

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