Potassium hydroxide catalysis

Ma.nufa.cture. The principal manufacturers of A/-vinyl-2-pyrrohdinone are ISP and BASF. Both consume most of their production captively as a monomer for the manufacture of PVP and copolymers. The vinylation of 2-pyrrohdinone is carried out under alkaline catalysis analogous to the vinylation of alcohols. 2-Pyrrohdinone is treated with ca 5% potassium hydroxide, then water and some pyrroHdinone are distilled at reduced pressure. A ca 1 1 mixture (by vol) of acetylene and nitrogen is heated at 150—160°C and ca 2 MPa (22 atm). Fresh 2-pyrrohdinone and catalyst are added continuously while product is withdrawn. Conversion is limited to ca 60% to avoid excessive formation of by-products. The A/-vinyl-2-pyrrohdinone is distilled at 70-85°C at 670 Pa (5 mm Hg) and the yield is 70-80% (8). 

In addition to the formulation parameters mentioned above, selection of the base used for catalysis has strong implications. Bases commonly used are sodium hydroxide, potassium hydroxide, lithium oxide, calcium hydroxide, barium hy-... 

Twenty weakly acidic drugs, including niclosamide, were determined by a nonaqueous catalytic thermometric titration method. Catalysis of the anionic polymerization of acetonitrile was used for endpoint indication. The solvent used was a mixture of acetonitrile and dimethylformamide or pyridine, and the titrant was sodium methoxide, potassium hydroxide, tertiary butanol, or tertiary butanol-sodium nitrite. Recoveries, limits of detection and relative standard deviations were tabulated [31]. 

The use of mesitoic acid esters has again been successfully employed by Burrows and Topping (1975) in the elucidation of intramolecular carbon acid participation. Under basic aqueous conditions, 2-acetylphenyl mesitoate [41] hydrolyses to yield mesitoic acid and 2-hydroxyacetophenone, reacting with intramolecular catalysis via the monoanion of the ketonic hydrate (see p. 192). However, in 47.5% aqueous ethanol containing potassium hydroxide, the reaction products from l-acetyl-2-naphthyl mesitoate [45] were found... 

In the first systematic study of the reaction between several different diary-loxalates, hydrogen peroxide, and fluorophores [3], it was recognised that the chemiluminescence reaction was highly sensitive to base catalysis by potassium hydroxide or benzyltrimethylammonium hydroxide, and that acidic conditions markedly diminished the light production. The addition of bases was noted to... 

In contrast, liquidiliquid phase-transfer catalysis is virtually ineffective for the conversion of a-bromoacetamides into aziridones (a-lactams). Maximum yields of only 17-23% have been reported [31, 32], using tetra-n-butylammonium hydrogen sulphate or benzyltriethylammonium bromide over a reaction time of 4-6 days. It is significant that a solidiliquid two-phase system, using solid potassium hydroxide in the presence of 18-crown-6 produces the aziridones in 50-94% yield [33], but there are no reports of the corresponding quaternary ammonium ion catalysed reaction. Under the liquidiliquid two-phase conditions, the major product of the reaction is the piperazine-2,5-dione, resulting from dimerization of the bromoacetamide [34, 38]. However, only moderate yields are isolated and a polymer-supported catalyst appears to provide the best results [34, 38], Significant side reactions result from nucleophilic displacement by the aqueous base to produce hydroxyamides and ethers. 

The physical properties of many macrocyclic polyethers and their salt complexes have been already described. - Dibenzo-18-crown-6 polyether is useful for the preparation of sharpmelting salt complexes. Dicyclohexyl-18-crown-6 polyether has the convenient property of solubilizing sodium and potassium salts in aprotic solvents, as exemplified by the formation of a toluene solution of the potassium hydroxide complex (Note 13). Crystals of potassium permanganate, potassium Lbutoxide, and potassium palladium(II) tetrachloride (PdClj + KCl) can be made to dissolve in liquid aromatic hydrocarbons merely by adding dicyclohexyl-18-crown-6 polyether. The solubilizing power of the saturated macrocyclic polyethers permits ionic reactions to occur in aprotic media. It is expected that this [)ropcrty will find practical use in catalysis, enhancement of... 

Although the preparation has been repeated, there have been no other reports of the type of reaction, (described in 1923) in which carbazole in the presence of excess potassium hydroxide and nitrobenzene at only 50°C gave a good yield of 9-(4-nitrophenyl)-carbazole, presumably via an adduct such as 43 subsequently oxidized by excess nitrobenzene and/or air. More recent examples of N-arylation of carbazoles have involved copper catalysis in reaction of aryl halides with carbazoles. Thus, copper bronze and potassium carbonate heated with the carbazole and the appropriate aromatic halide have produced 9-(4-methoxyphenyl)- and 9-(2-tolyl)carbazoles 9-(4-phenylphenyl)carbazole, l,4-di(carbazol-9-yl)benzene, 4,4 -di(carbazol-9-yl)biphenyl, and 9-(2-pyridyl)- and 9-(2-quinolyl)carbazoles 9-[2-(2-phenylphenyl)phenyl]- and 9-[2-(4-methylphenyl)phenyl] carbazoles 9-(3-bromo-6-nitrophenyl)-, 9-[3-(carbazol-9-yl]-, 9-(2-nitrophenyl)-, 9-(4-methyl-2-nitrophenyl)-, 9-(4-methoxycarbonyl)-l-nitro-, and l-nitro-9-(4-tolyl)carbazoles 9-(2-methoxycarbonylphenyl)carbazole 9-[2- 2-... 

Thus, dichloro- or dibromomethane in the presence of sodium hydride in solution in N,N-dimethylformamide gives O-methylene derivatives [73,74], Other conditions are also possible, for instance use of potassium hydroxide and dimfethylsulfoxyde [75], but an interesting development is the application of the phase-transfer catalysis technique, by which dibromomethane and sodium hydroxide in water, in the presence of an appropriate ammonium salt, leads to a cis-23-O-methylenation of methyl-4,6-O-benzylidene-a-D-mannopyranoside, [76] and simitar conditions afford the Other examples have been published [78]. 

Esters, on the other hand, are very common hydrolytic precursors to carboxylic acids. The traditional reaction for the hydrolysis of esters is basic saponification using sodium hydroxide or potassium hydroxide. While acid catalysis can also be employed, preparative methods usually use base catalysis because formation of the carboxylate salt drives the reaction to the right and gives high yields of products. 

It is reported that an industrial explosion was initiated by charging potassium hydroxide in place of potassium carbonate to the chloro-nitro compound in the sulfoxide [1], Dry potassium carbonate is a useful base for nucleophilic displacement of chlorine in such systems, reaction being controlled by addition of the nucleophile. The carbonate is not soluble in DMSO and possesses no significant nucleophilic activity itself. Hydroxides have, to create phenoxide salts as the first product. These are better nucleophiles than their progenitor, and also base-destabilised nitro compounds. Result heat and probable loss of control. As it nears its boiling point DMSO also becomes susceptible to exothermic breakdown, initially to methanethiol and formaldehyde. Methanethiolate is an even better nucleophile than a phenoxide and also a fairly proficient reducer of nitro-groups, while formaldehyde condenses with phenols under base catalysis in a reaction which has itself caused many an industrial runaway and explosion. There is thus a choice of routes to disaster. Industrial scale nucleophilic substitution on chloro-nitroaromatics has previously demonstrated considerable hazard in presence of water or hydroxide, even in solvents not themselves prone to exothermic decomposition [2],... 

A stereospecific synthesis of (S)-(—)-cathinone that utilizes the Friedel-Crafts reaction has been described (3/7). Reaction of the acid chloride obtained from /V-(methoxycarbonyl)-L-alanine (10) in benzene by A1C13 catalysis provided the N-protected a-amino ketone 11 with retention of chiralty 11 was deprotected by hydrolysis with potassium hydroxide. A more recently published method (408)... 

Crown ether catalysis of the reduction is also useful (Table I), with potassium hydroxide as the base and 18-crown-6 as the catalyst (18). 

The two-phase reduction of nitro compounds to anilines by Fe3(CO)i2, potassium hydroxide, and 18-crown-6 has previously been described (18). Crown ether catalysis (18-crown-6 or dicyclohexyl-18-crown-6) is also useful for reducing the double bond of the a,/3-unsaturated ketone, ben-zylideneacetone. Either of the following reaction systems can be employed Fe(CO)5/KOH/crown ether/benzene or Fe(C0)5/RNH2/Fl20/ crown ether/benzene (26). 

Benzylindazole and l-benzyl-4-bromo-3,5-dimethylpyrazole were efficiently debenzylated with potassium tert-butoxide in DMSO and oxygen at room temperature <2002TL399>. Alkylation of pyrazoles 443 with 2,2-dichloro-ethyl ether under conditions of phase-transfer catalysis gave A -[2-(2-chloroethoxy)ethyl]pyrazoles 444, which underwent dehydrochlorination with potassium hydroxide in DMSO giving A -(2-vinyloxyethyl)pyrazoles 445 (Scheme 51) <2004RJC1264>. 

Both anhydrous and hydrated sodium or potassium sulfide in ethanol have been used in the synthesis of thietanes. A common procedure is to use a solution of sodium or potassium hydroxide saturated with hydrogen sulfide. Liquid ammonia has been used as a solvent for the preparation of thietane (32%) from sodium sulfide and 1,3-dibromopropane. Phase-transfer catalysis has been used to good effect.A variation in which l,3-dichloro-3-methylbutane 3 is treated with aluminium chloride and hydrogen sulfide followed by aqueous sodium hydroxide gave 2,2-dimethylthietane 4 in 90% yield. An intermediate aluminium chloride-alkene complex, 5 or 6, was proposed. 

For the glycosylation of phenols with glycosyl halides, phase-transfer conditions using aqueous sodium or potassium hydroxide and quaternary ammonium salts have also been reported [89-94]. By using phase-transfer catalysis, a method for solid-phase synthesis of aryl glycosides was developed [95]. 

Claisen-Schmidt catalyst, R. Robinson s elegant method for the construction of ring A of steroids is illustrated by the synthesis of the bicyclic diketone (2). A Michael addition of 0.5 mole of 2-methylcyclohexane-l, 3-dione to methyl vinyl ketone under catalysis by methanolic potassium hydroxide gives (1), which is... 

These reactions have been used for the synthesis of cuparenones from p-methoxyacetophenone 135) (Scheme 98) and for the synthesis of permethylcyclo-pentanone, permethylcyclohexanone, and of permethylcyclohexane from acetone 224) (Scheme 99). If the carbon bearing the selenenyl moiety bears at least one hydrogen, reaction of thallium ethoxide in chloroform is described to lead instead to epoxides42 , and this was found to be the case234 for P-selenocylobutanols (Scheme 101). Closely related results have been observed when the reactions are performed under phase transfer catalysis simply with chloroform and potassium hydroxide as the dihalocarbene sources 235). 

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