Nitriles, acetylenic

In the first method a secondary acetylenic bromide is warmed in THF with an equivalent amount of copper(I) cyanide. We found that a small amount of anhydrous lithium bromide is necessary to effect solubilization of the copper cyanide. Primary acetylenic bromides, RCECCH Br, under these conditions afford mainly the acetylenic nitriles, RCsCCHjCsN (see Chapter VIII). The aqueous procedure for the allenic nitriles is more attractive, in our opinion, because only a catalytic amount of copper cyanide is required the reaction of the acetylenic bromide with the KClV.CuCN complex is faster than the reaction with KCN. Excellent yields of allenic nitriles can be obtained if the potassium cyanide is added at a moderate rate during the reaction. Excess of KCN has to be avoided, as it causes resinifi-cation of the allenic nitrile. In the case of propargyl bromide 1,1-substitution may also occur, but the propargyl cyanide immediately isomerizes under the influence of the potassium cyanide. 

The rule in carbon-13 NMR is that sp2-hybridized carbons (carbonyl, aromatic, olefinic) absorb at lowest field, followed by sp-hybridized (acetylenic, nitrile) and sp3 (aliphatic). A first glance leads us to believe we have seven signals, but we must remember that the methine carbon is directly bonded to phosphorus, so that we shall expect a relatively large C-P coupling. The other C-P couplings will probably be very much smaller. 

An intermolecular cyclotrimerization of an acetylenic nitrile was reported to proceed via the same alkyne-tantalum complex. The resultant pyridine derivative was obtained in 73% yield (Scheme 56).210... 

Recently, addition of organorhodium species to nitriles has been reported.420 4203 4201 Intermolecular reaction of benzonitrile with phenylborate (accompanied with r//w-aryiation) (Equation (65)), arylative cyclization of acetylenic nitriles (Equation (66)), and cyclization of 2-cyanophenylboronic acid with alkynes or strained alkenes (Equation (67)) are proposed to proceed via this process. 

Little is known as yet of the chemistry of the monocyclic 1,2,3-triazines. The only reactions that have been reported are hydrolysis to substituted butane-1,3-diones, photolytic decomposition to acetylenes, nitriles, and nitrogen, and high temperature (250°) thermolysis, which leads to loss of nitrogen and formation of the corresponding diarylindenone imines. The structures of the latter compounds were confirmed on the basis of their physical properties and by hydrolysis to the corresponding known diarylindenones. ... 

All the well-characterized 1,2,3-triazine derivatives are stable, high-melting solids. The 4,5,6-triaryl derivatives show UV maxima in the range 259-286 nm (log e = 4.09-4.42), 4,5-diphenyl-1,2,3-triazine has Amai at 251 nm, while the 4,5,6-trimethyl derivative shows two maxima at 217 nm (log e — 3.63) and 278 nm (log e = 2.79). Mass spectral studies indicate that fragmentation takes place in an identical fasMon to that observed during photochemical decomposition, i.e., with production of acetylenes, nitriles, and nitrogen. ... 

In the majority of cases alkyl hydrazines give single pyrazoles.160, 328, 336,337 In 1958 Bertrand established that allenic ketones give pyrazoles quantitatively with hydrazine.338 The reaction may be formulated as follows, the second stage being stabilization by aromatization. Acetylenic nitriles give aminopyrazoles with hydrazine.339... 

Acetylenic nitriles are best prepared by heating the corresponding iodides with alkali cyanides in aqueous acetone or with cuprous cyanide in xylene. With methanolic potassium cyanide, 1-chloro-l-heptyne yields a cyanovinyl ether of the structure C,H C(OCHj) = CHCN which results from the addition of methanol to the triple bond. ... 

Although the sp-hybridized carbon atoms are commonly found in acetylenes, nitriles, allenes, carbon dioxide, etc., heavy group-14 element analogs of these compounds are very rare [16, 17]. The first silicon compound with a formal s/i-silicon atom, trisilaallene 12, was synthesized as a dark green solid using two-step reactions from stable dialkylsilylene 13 [18] in overall 42% yield (Scheme 5) [19]. Trisilaallene 12 is sensitive to air but thermally rather stable, with a melting point of 198-200 °C. 

With a,j -acetylenic nitriles, acetylenic organomagnesium compounds produce only the ketones resulting from 1,2-addition [4], Recently, the 1,4-addition of RMgX (R = saturated, vinylic, or allylic groups) and other organometallics to the conjugated structure of a-ethylidene-(Z)-1//-indole-2-acetonitrile has been observed [38] ... 

The reduction of a,p-acetylenic nitriles to -a,p-ethylenic nitriles by 0.5 equivalents of LAH in Et20 under reflux [VK4] or NaBH in EtOH [KS6] has been described. 

Enaminones [3213 and ketene dithioacetals (reviews [3712,3830] and a recent synthesis [3965]) are being widely used and tailored to particular requirements [3822]. Allenic and acetylenic nitriles cyclize 2-aminopyridines on heating in dichloromethane [3397]. 

In general, pyrolysis of monocyclic 1,2,3-triazines 1 leads to acetylenes, nitriles and nitrogen.46, 295 297 300 Heating simple 1,2,3-triazines in a sealed tube led to the isolation of pyridines, pyrimidines, pyrazoles, pyrroles, pyridazine, and indeno[3,2-/>]pyridine, depending on the substituents bound to the 1,2,3-triazine ring and the reaction conditions.46 A mechanism formulated for the formation of these products involves an azete as an intermediate. 

Photochemistry of monocyclic 1,2,3-triazines has not been studied very intensively. The main route on photolysis is the fragmentation into acetylenes, nitriles and nitrogen. 

Acetylenic nitriles and amides were converted by Moureu and Lazennec91 into the corresponding keto nitriles and keto amides by boiling their alcoholic solutions with amines. 

Imidazolines.— The double Michael addition of 1,2-diamines to allenic or acetylenic nitriles provides a convenient route to imidazolines (Scheme 105). Imidazolines are also available from di-immonium dibromides and N-alkyl- or JV-aryl-amidines. Imidazolidin-2-ones are obtained by anodic addition of 1,3-dimethylurea to hexa-2,4-diene and related derivatives. 

From o-Aminobenzenethiols (Type A S—C H4—N + C).—An improvement on the standard procedures (milder conditions) is the use of DMF dimethyl acetal instead of formic acid or alkyl orthoformates. A 64% yield of benzothiazolin-2-one is obtained when o-aminobenzenethiol is treated sequentially with carbon monoxide and oxygen in the presence of triethylamine and selenium in DMF. o-Aminobenzenethiol forms substituted vinylamine adducts with acetylenic nitriles RC=CCN. These cyclize in the presence of sodium ethoxide, and the products lose acetonitrile on distillation at atmospheric pressure to give 2-sub-... 

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