Potassium butoxide

The amide group is readily hydrolyzed to acrylic acid, and this reaction is kinetically faster in base than in acid solutions (5,32,33). However, hydrolysis of N-alkyl derivatives proceeds at slower rates. The presence of an electron-with-drawing group on nitrogen not only facilitates hydrolysis but also affects the polymerization behavior of these derivatives (34,35). With concentrated sulfuric acid, acrylamide forms acrylamide sulfate salt, the intermediate of the former sulfuric acid process for producing acrylamide commercially. Further reaction of the salt with alcohols produces acrylate esters (5). In strongly alkaline anhydrous solutions a potassium salt can be formed by reaction with potassium / /-butoxide in tert-huty alcohol at room temperature (36). 

Sulfoxides containing P-hydiogen atoms, eg, di-Abutylsulfoxide [2211 -92-9] react with strongly basic systems, eg, potassium /-butoxide, in DMSO by sulfenic acid elimination to produce olefins (eq.l2) (44) ... 

B. (l-Azido-3,3-dimethoxy-l-propenyl)benzene. In a 2-1., one-necked, round-bottomed flask equipped with a magnetic stirrer and powder funnel are placed 156 g. (0.45 mole) of the iodoazide from Part A and 1500 ml. of anhydrous ether. The solution is stirred and cooled in an ice-salt bath (— 5° to 0°), and 62 g. (0.55 mole) of potassium <-butoxide (Note 6) is added. The powder funnel is then replaced by a calcium chloride drying tube and the mixture is stirred for 4 5 hours at 0°. At the end of this time 350 ml. of water is added while the mixture is still cold. The ethereal layer is then separated and washed with three 350-ml. portions of water and dried over magnesium sulfate. The solvent is removed with a rotary evaporator without heating, leaving 67-75 g. (68-76%) of (l-azido-3,3-dimethoxy-l-propenyl)-benzene as a dark oily liquid (Note 7). This material can be used without further purification for Part C (Note 8). 

Ester eliminations are normally one of two types, base catalyzed or pyrolytic. The usual choice for base catalyzed j5-elimination is a sulfonate ester, generally the tosylate or mesylate. The traditional conditions for elimination are treatment with refluxing collidine or other pyridine base, and rearrangement may occur. Alternative conditions include treatment with variously prepared aluminas, amide-metal halide-carbonate combinations, and recently, the use of DMSO either alone or in the presence of potassium -butoxide. 

Dimethyl sulfoxide (DMSO) has been used to effect the elimination of sulfonates at elevated temperatures (see, for example, ref. 237). Benzene-sulfonates are recommended. The elimination of a variety of sulfonates proceeds readily in this medium in the presence of potassium /-butoxide. A -Compounds have been formed at 100°, but heating is not necessary. The effects of temperature change, orientation of the hydroxy group and changes in the sulfonate employed have been examined. The principal side reaction appears to be formation of the original alcohol (uninverted), particularly with equatorial mesylates at low temperatures it is minimized with axial tosylates. 

The method of choice for the preparation of cholesta-3,5-diene is treatment of cholesteryl tosylate with potassium /-butoxide in DMSO. The mesylate and chloride react similarly. 

Such eliminations can usually be achieved under the conditions which work for sulfonates (e.g. bromides on alumina " ), and the anti-coplanar arrangement appears to be preferred. A large difference in reaction rate between the epimeric 3-chloro-5a-cholestanes has been observed in DMSO-potassium /-butoxide. ... 

In any event, isolation is tedious and yields of single olefin are not very good, although the use of potassium /-butoxide is reported to favor... 

The Roussel group has described recently a novel method for the synthesis of 2,2-dimethyl-A" -3-keto steroids. Thus addition of potassium t-butoxide to a solution of 19-nortestosterone (25) in tetrahydrofuran containing methyl iodide and hexamethylphosphorous triamide at —70° affords the 2,2-dimethyl compound (26) in good yield.Methylation of A" -3-ketone by the classical conditions, namely addition of methyl iodide to a solution of the steroid and potassium /-butoxide, leads to the 4,4-dimethyl product. 

Treatment of dichlorocyclopropane (35) first with pyridine to give chloro-diene (36) followed by potassium /-butoxide affords 1-ethoxycyclohepta-1,3,5-triene (37) in 55% overall yield from dichlorocarbene adduct (35). 

Potassium /-butoxide is prepared by dissolving potassium metal in t-butanol followed by removal of the excess of -butanol by distillation under reduced pressure. The resultant cake is powdered and used directly in the dibromocarbene additions. 

Diketo steroids have been prepared by air oxidation of 3-keto-5i5-steroids in potassium /-butoxide-t-butanoF or by hydrolysis of 4,5-epoxy-3-ketones followed by dehydration. However, the most general synthesis is that used by Camerino et al. to prepare Vketo-A-norandrostanes and pregnanes. Hydroxylation of 17a,20.20,21-bismethylenedioxypregn-... 

A solution of ketone (85) in t-butanol and excess potassium -butoxide and potassium hydroxide is heated at refluxjinder an atmosphere of oxygen for 8 hr to give the C-norpregnane acid (87), in about 46% yield. Yields tend... 

Equations 1-10 illustrate some mild methods that can be used to cleave amides. Equations 1 and 2 indicate the conditions that were used by Woodward and Eschenmoser, respectively, in their synthesis of vitamin B12. Butyl nitrite, nitrosyl chloride, and nitrosonium tetrafluoroborate (NO BF4 ) have also been used to cleave amides. Since only tertiary amides are cleaved by potassium -butoxide (eq. 3), this method can be used to effect selective cleavage of tertiary amides in the presence of primary or secondary amides.(Esters, however, are cleaved by similar conditions.) Photolytic cleavage of nitro amides (eq. 4) is discussed in a review. 

Haloforms react with potassium /-butoxide to form dihalocarbenes, which add smoothly to olefins giving 1,1-dihalocyclopropanes (2). The reaction does not appear... 

In a dry, 250 ml, three-necked flask equipped with a dropping funnel and magnetic stirrer are placed 40 ml of dry /-butyl alcohol (distilled from calcium hydride) and 4.0 g (0.036 mole) of potassium /-butoxide. The solution is cooled in ice and 40 g (49 ml, 0.49 mole) of dry cyclohexene is added. Bromoform (10 g, 3.5 ml, 0.039 mole) is added to the cooled, stirred reaction vessel dropwise over about hour, and the vessel is stirred an additional hour with the ice bath removed. The reaction mixture is poured into water (approx. 150 ml), and the layers are separated. The aqueous layer is extracted with 25 mi of pentane, and the extract is combined with the organic layer. The combined layers are dried (sodium sulfate), and the solvent is removed. The product is purified by distillation, bp 10078 mm. 

A dry, 500-ml, three-necked flask is fitted with a mechanical stirrer, a condenser, and a pressure-equalizing dropping funnel. The system is swept out with nitrogen and a slight positive pressure of nitrogen is maintained by venting the system to a mercury filled U-tube. In the flask is placed 21 g (0.187 mole) of dry potassium /-butoxide, and the flask is cooled in an ice-salt bath. 

A 250-ml three-necked flask is fitted with a condenser (drying tube). The system is flushed with dry nitrogen, and a dry nitrogen atmosphere is maintained. In the flask is placed a solution of potassium /-butoxide (2.8 g, 0.025 mole) in dry /-butyl alcohol (100 ml). 4-Benzoyloxycyclohexanone (5 g, 0.022 mole, Chapter 7, Section X) is added to the solution, the transfer being assisted by the use of 10-15 ml of dry /-butyl alcohol. The mixture is cautiously brought to reflux, and refluxing is continued for 45 minutes. The mixture is then cooled rapidly to room temperature and carefully acidified by the addition of 10 ml of 6 A hydrochloric acid (potassium chloride will precipitate). The mixture is placed on a rotary evaporator and the bulk of the solvent is removed. The residue is diluted with sufficient water to dissolve the potassium chloride and extracted three times with 50-ml portions of ether. The ether extracts are combined and extracted four times with 100-ml portions of aqueous 5% sodium bicarbonate solution. The bicarbonate extracts are combined and the solution is acidified by the addition of concentrated hydrochloric acid to pH 4. The mixture is now extracted three times with 100-ml portions of ether, the combined ethereal extracts are washed with water, then dried, and the solvent is removed. The residual product may be recrystallized from benzene-hexane. The acid has mp 65-68°. 

I. Zinc-copper couple (Chapter 13, Section I) Alpha Inorganics Potassium /-butoxide MCB cM-Cyclooctcne A, MCB Sodium trichloroacetate EK... 

Elimination reactions involve loss of two substituents from adjacent atoms as a result unsaturation is introduced. In many instances additional reagents are required to cause the elimination to occur, reducing the overall atom economy still further. A simple example of this is the E2 elimination of HBr from 2-bromopropane using potassium -butoxide (Scheme 1.12). In this case unwanted potassium bromide and /-butanol are also produced reducing the atom economy to a low 17%. 

An interesting reaction of dimsyl anion 88 is the methylation of polyaromatic compounds. Thus naphthalene, anthracene, phenanthrene, acridine, quinoline, isoquinoline and phenanthridine were regiospecifically methylated upon treatment with potassium -butoxide and DMSO in digyme or with sodium hydride in Since... 

The benzyl 1,2,4-thiadiazolium salt 59 can be isomerized to the 5-imino-l,2,4-thiadiazolidine 60 when treated with a strong base like potassium /-butoxide (Equation 17) <1997ZOR1728>. If the 2-substituent is replaced with a tosylmethyl group and the 5-position substituent is a diphenylamino in place of an aniline such as compound 61, then a rearrangement occurs to give an imidazole 62 (Equation 18) <1997ZOR1728>. 

Otera and coworkers developed an alternative procedure to the Julia method for generating dienes or alkynes in the same reaction by the double elimination of /J-acetoxy or /1-alkoxy sulphones with potassium /-butoxide (equation 58)98,99. The reaction pathway leading to the diene or an alkyne depends on the substrate structure and the reaction conditions. If an allylic hydrogen is present in the substrate then diene is formed, otherwise, the alkyne is the product of the reaction. This modified Julia methodology has een applied to the synthesis of vitamin A (equation 59)100, alkaloids piperine (equation and trichonine (equation 61)102. 

Potassium acetate, reaction with N,N-dichlorocyclohexylamine, 46,17 Potassium amide, 48, 41 Potassium / butoxide, 46, 33 alcohol-free, reaction with bromo-benzene, 46, 89... 

As mentioned already in CHEC-II(1996) <1996CHEC-II(8)411>, some tetrazolo[l,5- ]pyridines can react with their C(5)-C(6) and C(7)-C(8) double bonds as dienophiles in Diels-Alder reactions. A novel study again supported this recognition Goumont et al. described that 6,8-dinitrotetrazolo[l,5- ]pyridine 11 easily react with some 2,3-disub-stituted butadienes to give bis-cycloadducts 48 <2002T3249>. These products when treated with potassium /-butoxide undergo base catalyzed elimination of nitric acid followed by oxidation reaction to yield the fully aromatic tetracyclic compounds 49 (Scheme 14). 

During the process of preparing these molecules, we observed that compounds 5 and 6, formed oligomers when mixed with a strong base (e.g., potassium /-butoxide) in polar aprotic solvent. Detailed studies under controlled... 

The yield of 11,ll-dichlorotricyclo[4.4.1.01,6]undeca-3,8-diene strongly depends on the quality of the potassium <-butoxide used. Commercially available, sublimed potassium i-butoxide was employed. When freshly sublimed potassium f-butoxide is utilized, yields of up to 45% of 11,ll-dichlorotricyclo[4.4.1.01- ]undeca-3,8-diene can be obtained. Potassium <-butoxide, prepared by the method of Doering, gave yields comparable to those achieved with the commercial product. 

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