Potassium hydroxide , as base

In the early studies on luminol and related hydrazides the systems used were composed of either sodium or potassium hydroxide, as base, hydrogen peroxide as the oxidizing agent (more recently molecular oxygen, hypochlorite, iodide, and permanganate have also been used), and some type of initiator or activator. This initiator was frequently hypochlorite, persulfate, a transition metal... 

Typically, reactions are carried out open to air, at room temperature (rt), using a mixture of tBuOH/water (9 1) or MeCN/water (9 1) as solvent and sodium or potassium hydroxide as base. The presence of water suppresses undesired side reactions (e.g., Cannizzaro reaction, Williamson alkylation, solvent reactivity) [37]. Benzyl bromides are most commonly reported as the halide component. 

Theoretically, in a simple kinetic resolution the ee value should not exceed 32 % at this specific conversion. In addition to the rhodium complex, this reaction requires acetophenone as stoichiometric hydride acceptor, phenanthroline as coligand and potassium hydroxide as base. An ee value of 98 % at 60 % conversion (theoretical value 67 %)is achieved with [Rh2(OAc)4] without an added base after 3 days. Surprisingly, the enzyme tolerates potassium hydroxide in amounts up to 20 mol% at elevated temperatures however, the enantiomeric excesses are somewhat lower than those obtained in an ordinary kinetic resolution. Unselective, base- or metal-catalyzed acylation might be the reason for the somewhat lower ee value. 

Chlorofluorocarbene. Schlosser et al. have found that this crown ether is significantly superior to the commonly used ammonium salts for generation of chlorofluorocarbene from dichlorofluoromethane by the two-phase technique. They used potassium hydroxide as base rather than sodium hydroxide, since crown ethers bind potassium ions more selectively than sodium ions. They used the carbene for synthesis of fluorodienes. The method is illustrated for the conversion of methallyl chloride (1) into 2-fluoro-3-methyl-l, 3-butadiene (3-fluoro-isoprene), (4). The conversion of (3) into (4) involves a 1,4-elimination of ICl ... 

As a demonstration of the complete synthesis of a pharmaceutical in an ionic liquid, Pravadoline was selected, as the synthesis combines a Friedel-Crafts reaction and a nucleophilic displacement reaction (Scheme 5.1-24) [53]. The allcylation of 2-methylindole with l-(N-morpholino)-2-chloroethane occurs readily in [BMIM][PF6] and [BMMIM][PF6] (BMMIM = l-butyl-2,3-dimethylimida2olium), in 95-99 % yields, with potassium hydroxide as the base. The Friedel-Crafts acylation step in [BMIM][PF6] at 150 °C occurs in 95 % yield and requires no catalyst. 

The solution is prepared by dissolving 22.3 g (105 mmol) of potassium phosphate (Nakarai Chemicals, Japan) in water and adjusting the final volume to 35 mL. The original method5 used sodium hydroxide as base potassium phosphate is desirable for the extension of the present procedure to base-sensitive compounds. Under such conditions, the reaction with 9-(10-carbomethoxydecanyl)-9-BBN proceeds similarly without saponification of the ester group. 

Several methods have been developed for preparation of /3 lactose. a-Lactose hydrate has been converted to /3-lactose in nearly quantitative yield by refluxing in methanol containing small amounts of sodium hydroxide (Olano and Rios 1978) ethanol, n-propanol and n-buta-nol were also effective as solvents (Olano 1978). Similarly, a-lactose hydrate was converted to /3-lactose with potassium methoxide or potassium hydroxide as the base (Parrish et al. 1979B). /3-Lactose was also prepared from the anhydrous forms of a-lactose if small amounts of /3-lactose were present (Parrish et al. 1980A). 

Primary alkaline cells use sodium hydroxide or potassium hydroxide as tlie electrolyte. They can be made using a variety of chemistries and physical constructions. The alkaline cells of the 1990s are mostly of the limited electrolyte, dry cell type. Most primary alkaline cells are made sing zinc as the anode material a variety of cathode materials can be used. Primary alkaline cells are commonly divided into tW o classes, based on type of construction the larger, cylindrically shaped batteries, and the miniature, button-type cells. Cylindrical alkaline batteries are mainly produced using zinc-manganese dioxide chemistry, although some cylindrical zinc-mercury oxide cells are made. 

Partial benzylation with powdered potassium hydroxide as a base and toluene as a solvent was used some 50 years ago for the preparation of 1,6-anhydro-2,4-0-benzyl-P-D-glucopyranose [79]. Since that time, other solvents, such as benzene [80-82], 1,4-dioxane-toluene mixtures [83, 84], or excess benzyl chloride [82, 85] were used as well, with apparent effects on the regioselectivity. Thus, the axially oriented secondary hydroxyl group of lL-l,2,3,4-tetra-0-benzyl-c/i ro-inositol is more reactive than the equatorial one using benzyl chloride alone (ratio of 79 21), whereas the opposite is true (35 65) in benzene as a solvent [82]. Benzylation of myo-inositol derivatives in the latter solvent was also described [80, 81, 86]. 

Carbanions can be generated and alkylated in a two-phase liquid-liquid system using concentrated aqueous sodium or potassium hydroxide as the base. Makosza has shown that deprotonation occurs at the interface, Fig. 5.10 [12]. 

A similar approach was reported by Lygo and co-workers who applied comparable anthracenylmethyl-based ammonium salts of type 26 in combination with 50% aqueous potassium hydroxide as a basic system at room temperature [26, 27a], Under these conditions the required O-alkylation at the alkaloid catalyst s hydroxyl group occurs in situ. The enantioselective alkylation reactions proceeded with somewhat lower enantioselectivity (up to 91% ee) compared with the results obtained with the Corey catalyst 25. The overall yields of esters of type 27 (obtained after imine hydrolysis) were in the range 40 to 86% [26]. A selected example is shown in Scheme 3.7. Because the pseudo-enantiomeric catalyst pairs 25 and 26 led to opposite enantiomers with comparable enantioselectivity, this procedure enables convenient access to both enantiomers. Recently, the Lygo group reported an in situ-preparation of the alkaloid-based phase transfer catalyst [27b] as well as the application of a new, highly effective phase-transfer catalyst derived from a-methyl-naphthylamine, which was found by screening of a catalyst library [27c],... 

M-OH (metal hydroxide) Sodium hydroxide Potassium hydroxide Nucleophilic bases Deprotonation of organic acids with acidities as high as pKa = 16, hydrolysis of esters, amides, and nitriles... 

The transformation to the 1,2,3,4-tetrahydro derivatives is best accomplished by hydrogenating the 2-alkyl-p-carboline salts in methanol adjusted to pH 10 with potassium hydroxide, as shown for alstonine hydrochloride (37) (eq. 12.65),124 or hydrogenating the anhydronium base in methanol, as shown with 2-methylharman (38) (eq. 12.66).125... 

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). 

Selective protection of 3-aminopyrazoles can lead to a variety of 3-acylaminopyrazole derivatives. 3-Aminopyrazole 317 could be selectively protected at N-2 giving BOC-protected pyrazole 318, which reacted with various acyl chlorides followed by BOG removal to provide 3-acylated pyrazoles 319 (Scheme 30) <2003TL4491>. Other protecting groups such as carbobenzyloxy (Cbz), benzyl (Bn), and SEM could be introduced at the N-2 position with biphasic conditions using potassium hydroxide as the base. A simple procedure for the BOG protection of H-1 of 3-aminopyrazoles has been described where 3-acylaminopyrazole derivatives could be prepared in good yields <2005TL933>. 

The literature procedure for condensation of benzil with 1,3-diphenyl-acetone in ethanol with potassium hydroxide as basic catalyst suffers from the low boiling point of the alcohol and the limited solubility of both potassium hydroxide and the reaction product in this solvent. Triethylene glycol is a better solvent and permits operation at a higher temperature. In the procedure that follows, the glycol is used with benzyl-trimethylammonium hydroxide, a strong base readily soluble in organic solvents, which serves as catalyst. 

The redox-active natural product (+)-methanophenazine (MP) is the first phenazine to be isolated from archea. This compound is able to mediate the electron transport between membrane-bound enzymes and was characterized as the first phenazine derivative involved in the electron transport of biological systems. The research team of U. Beifuss prepared this natural product by using the Williamson ether synthesis in the last step of the synthetic sequence. The etherification was conducted under phase-transfer conditions in a THF/water system in the presence of methyltrioctyl-ammonium chloride and using potassium hydroxide as a base. 

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