Potassium amide in conversion

Potassium amide in conversion of o-acetoacetochloroanilide to 3-acetyloxindole, 40, 1 Potassium tert-butoxide, 41, 101 in dehydration of formamides to isocyanides, 41, 101... 

Phenylpyrimidine. On treatment of 4-phenylpyrimidine with potassium amide in liquid ammonia at 33°C for 70 hr in the presence of potassium nitrate, followed by quenching the reaction mixture by addition of ammonium chloride and workup, two products were isolated 2-amino-4-phenylpyrimidine (60%) and 6-amino-4-phenylpyrimidine (15%) (79JOC4677). When the reaction was carried out with labeled potassium amide in liquid ammonia and using the combined methodologies of chemical conversions and mass spectrometry as discussed previously (see Section II,C,l,a) it was found that in 6-amino-4-phenylpyrimidine (62/63), hardly any label was incorporated in the ring ( 5%), but that about... 

After Abe s work the problem again lay dormant for a number of years until it was taken up by Wilmarth and his co-workers. Claeys, Baes, and Wilmarth (29) in 1948 reported that a liquid ammonia solution of potassium metal rapidly catalyzed o-p H2 conversion, a half-time in solution of 37 sec. being obtained at —53°. In order to establish that this result was due to dissolved metal and not to amide ion impurity, Claeys, Dayton, and Wilmarth (30) studied the o-p H2 conversion in the presence of potassium amide in liquid ammonia. Rates were obtained comparable with those occurring with the metal solution. The mechanism of the conversion was different for the two cases, however, since the amide solution also catalyzed exchange between gaseous deuterium and liquid ammonia, while the metal solution did not. It was assumed that the metal acted by a paramagnetic mechanism and the amide ion by a chemical mechanism. In the same note Claeys, Dayton, and Wilmarth (30) reported confirmation of Wirtz and Bonhoeffer s results on the aqueous alkali system and questioned the validity of Abe s objections. 

There are considerable data available on imidazole formation by ring contractions of pyrimidines, pyrazincs and triazines [15, 43, 59-61]. Few of the reactions, however, have synthetic potential except perhaps for the thermolytic conversions of azidopyrimidines and azidopyrazines into 1-cyano-substituled imidazoles, and the reactions of chloropyrimidines and chloropyrazines with potassium amide in liquid ammonia to give 4- and 2-cyanoimidazoles, respectively. Ring contractions of quinoxaline 1-oxides may also have some applications. 

The reaction of 2potassium amide in liquid ammonia to give 2-cyanoimidazole, imidazole, and 2-aminopyridine has been investigated (911). It has been found that 2-chloropyrazine containing an excess of in position 1, on treatment with potassium amide in liquid ammonia at — 65° yields 2-aminopyrazine in which the exocyclic nitrogen contains all the excess and an addition-nucleophilic-ring opening-ring closure (ANRORC) mechanism was proposed (822). The mechanism of the conversions into imidazole (823) and... 

Thus 500 ml. of commercial anhydrous liquid anunonia is introduced into the flask from a cylinder through an inlet tube. The liquid is stirred, and a 0.5-g. piece of potassium is removed from a container of kerosene, blotted with filter paper, and added. After the appearance of a blue color about 0.25 g. of ferric nitrate hydrate is added, followed by 0.5-g. pieces of potassium until 9 g. (0.23 mole) has been added. Discharge of the deep blue color after about 20 min. indicates complete conversion to potassium amide. In contrast to sodamide and lithium amide, which form suspensions in liquid ammonia, potassium amide appears to be mostly in solution, although the solutions are opaque and have been regarded by some workers as suspensions. 

Shortly after the publication of the tr-adducts from diazines, Zoltewicz and co-workers reported the identification of anionic a-adducts from treating quinoline and isoquinoline with excess potassium amide in liquid ammonia. H-NMR studies showed that 1-amino-1,2-dihydroisoquinolinide (21) was formed with isoquinoline. In the case of quinoline, kinetic and thermodynamic products were observed. At — 45°C, adduct formation between quinoline and sodium or potassium amide in liquid ammonia, gave a mixture of 2-amino-l,2-dihydroquinolinide (22) and 4-amino-l,4-dihydroquinolinide (23), with the former compound being predominant. Warming the mixture resulted in irreversible conversion of 22 into the more stable 23. 

Aldehyde enolates and aldehydes are extremely reactive and therefore, to avoid undesirable side reactions, fast and quantitative conversion of aldehydes to enolates is necessary. Strong bases are needed, e.g. potassium amide in liquid ammonia or potassium hydride in THF. Aldehyde enolates are very rarely used in organic synthesis. 

Benzoxazoles. - Both o- and m-halogenobenzanilides (413) are converted into the amidines (415) by potassium amide in liquid ammonia these are formed by aryne cyclization to 2-phenylbenzoxazole (414) and subsequent aminoly-sis." The conversion of acetophenone oxime into 2-methylbenzoxazole by the action of phosphorus oxychloride involves a Beckmann rearrangement. Pyrolysis of aryl azidoformates, ArOaCNa, gives benzoxazol-2-ones. The azide (416) is converted into the benzoxazole (417) on heating. The... 

In order to minimize the chance of this isomerization, the deprotonation is carried out at a low temperature (strongly cooled liquid ammonia). The use of the soluble, and therefore kinetically more active, potassium amide, in combination with a large excess of 1 -methylcyclopropene, warrants a sufficiently fast conversion into the cyclopropenyl anion. Ammonia is a particularly suitable solvent for alkylation reactions. As expected from its higher basicity the anion of 1-methylcyclopropene reacts more easily with bromohexane than do acetylides (compare Ref. [6]). 

A dehydroannulene has also been implicated in the conversion, by potassium amide in liquid ammonia, of 1,6-oxido[10]annulene into the potassium salt of a-naphthol [150],... 

Intramolecular Cyclizations.—Base-induced 1,3-bonding occurs in the conversion of (24) into (25) even though the reaction is a 1,7-elimination. A spiro-product is also obtained in the dehydration of (26) with dicyclohexyl-carbodi-imide (DCQ. The mechanism of the 1,3-elimination from 3-phenyl-propyltrimethylammonium iodide with potassium amide in liquid ammonia has been investigated. The reaction is concurrent with 1,2-elimmation and shows a nitrogen kinetic isotope effect = 1.022 + 0.001). This and deuterium-... 

This isomerization, which must proceed through a 1,2,3-trienylanine, is not "contra-thermodynamic", since with a catalytic amount of potassium tert.-butoxide the same result is obtained. Enyne ethers, H2C=CH-CsC-0R, undergo a similar conversion into HCeC-CH=CH-OR upon interaction with alkali metal amides in liquid NH3, followed by hydrolysis . Enyne sulphides, H2C=CH-CsC-SR, and the hydrocarbons H2C=CH-CsC-R (R = or phenyl) give only tars or polymeric products under... 

Potassium dissolves in Hquid ammonia, but the conversion of a small amount of the metallic potassium to the metallic amide takes several days. By applying the same technique using sodium metal, sodium amide [7782-92-5] NaNH2, a white soHd, can be formed. 

When a cold (-78 °C) solution of the lithium enolate derived from amide 6 is treated successively with a,/ -unsaturated ester 7 and homogeranyl iodide 8, intermediate 9 is produced in 87% yield (see Scheme 2). All of the carbon atoms that will constitute the complex pentacyclic framework of 1 are introduced in this one-pot operation. After some careful experimentation, a three-step reaction sequence was found to be necessary to accomplish the conversion of both the amide and methyl ester functions to aldehyde groups. Thus, a complete reduction of the methyl ester with diisobutylalu-minum hydride (Dibal-H) furnishes hydroxy amide 10 which is then hydrolyzed with potassium hydroxide in aqueous ethanol. After acidification of the saponification mixture, a 1 1 mixture of diastereomeric 5-lactones 11 is obtained in quantitative yield. Under the harsh conditions required to achieve the hydrolysis of the amide in 10, the stereogenic center bearing the benzyloxypropyl side chain epimerized. Nevertheless, this seemingly unfortunate circumstance is ultimately of no consequence because this carbon will eventually become part of the planar azadiene. 

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