Potassium carbonyl compounds

The carbonyl compound may be mixed with an aqueous solution of sodium or potassium cyanide and mineral acid is added, or the bisulphite compound may be treated with an equivalent quantity of sodium cyanide, for example ... 

Reductive coupling of carbonyl compounds to yield olefins is achieved with titanium (0), which is freshly prepared by reduction of titanium(III) salts with LiAIH4 or with potassium. The removal of two carbonyl oxygen atoms is driven by T1O2 formation- Yields are often excellent even with sensitive or highly hindered olefins. (J.E. McMurry, 1974, 1976A,B). 

Synthetically useful stereoselective reductions have been possible with cyclic carbonyl compounds of rigid conformation. Reduction of substituted cyclohexanone and cyclopentan-one rings by hydrides of moderate activity, e.g. NaBH (J.-L. Luche, 1978), leads to alcohols via hydride addition to the less hindered side of the carbonyl group. Hydrides with bulky substituents 3IQ especially useful for such regio- and stereoselective reductions, e.g. lithium hydrotri-t-butoxyaluminate (C.H. Kuo, 1968) and lithium or potassium tri-sec-butylhydro-borates or hydrotri-sec-isoamylborates (=L-, K-, LS- and KS-Selectrides ) (H.C. Brown, 1972 B C.A. Brown, 1973 S. Krishnamurthy, 1976). 

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

The addition of hydrogen cyanide is catalyzed by cyanide ion but HCN is too weak an acid to provide enough C=N for the reaction to proceed at a reasonable rate Cyanohydrins are therefore normally prepared by adding an acid to a solution containing the carbonyl compound and sodium or potassium cyanide This procedure ensures that free cyanide ion is always present m amounts sufficient to increase the rate of the reaction... 

Ma.nufa.cture. In general, manufacture is carried out in batch reactors at close to atmospheric pressure. A moderate excess of finely divided potassium hydroxide is suspended in a solvent such as 1,2-dimethoxyethane. The carbonyl compound is added, followed by acetylene. The reaction is rapid and exothermic. At temperatures below 5°C the product is almost exclusively the alcohol. At 25—30°C the glycol predominates. Such synthesis also... 

The direct synthesis of o.g-unsaturated nitriles can be accomplished by treating the appropriate carbonyl compound with potassium hydroxide in... 

Structural effects on the rates of deprotonation of ketones have also been studied using veiy strong bases under conditions where complete conversion to the enolate occurs. In solvents such as THF or DME, bases such as lithium di-/-propylamide (LDA) and potassium hexamethyldisilylamide (KHMDS) give solutions of the enolates in relative proportions that reflect the relative rates of removal of the different protons in the carbonyl compound (kinetic control). The least hindered proton is removed most rapidly under these... 

Enamines derived from aldehydes can usually be obtained by the reaction of 2 equivalents of a secondary amine with the carbonyl compound, in the presence of anhydrous potassium carbonate, followed by pyrolytic distillation of the aminal with elimination of one of the amine groups (10,15, 30-36). Ketones are directly converted to enamines under the conditions of aminal formation. The azeotropic removal of water with excess aldehyde has also been described (32,37). 

Perhaps because of inadequate or non-existent back-bonding (p. 923), the only neutral, binary carbonyl so far reported is Ti(CO)g which has been produced by condensation of titanium metal vapour with CO in a matrix of inert gases at 10-15 K, and identified spectroscopically. By contrast, if MCI4 (M = Ti, Zr) in dimethoxy-ethane is reduced with potassium naphthalenide in the presence of a crown ether (to complex the K+) under an atmosphere of CO, [M(CO)g] salts are produced. These not only involve the metals in the exceptionally low formal oxidation state of —2 but are thermally stable up to 200 and 130°C respectively. However, the majority of their carbonyl compounds are stabilized by n-bonded ligands, usually cyclopentadienyl, as in [M(/j5-C5H5)2(CO)2] (Fig. 21.8). 

The formation of hydantoin (2) from carbonyl compound 1 with potassium cyanide and ammonium carbonate or from cyanohydrin 3 and ammonium carbonate is referred to as... 

In summary, the Bucherer-Bergs reaction converts aldehydes or ketones to the corresponding hydantoins. It is often carried out by treating the carbonyl compounds with potassium cyanide and ammonium carbonate in 50% aqueous ethanol. The resulting hydantoins, often of pharmacological importance, may also serve as the intermediates for amino acid synthesis. 

The carbonyl compound to be reduced (0.1 mole) is placed in a 250-ml round-bottom flask with 13.5 g of potassium hydroxide, 10 ml of 85% hydrazine hydrate, and 1(X) ml of diethylene glycol. A reflux condenser is attached and the mixture is heated to reflux for I hour (mantle). After refluxing 1 hour, the condenser is removed and a thermometer is immersed in the reaction mixture while slow boiling is continued to remove water. When the pot temperature has reached 200°, the condenser is replaced and refluxing is continued for an additional 3 hours. The mixture is then cooled, acidified with concentrated hydrochloric acid, and extracted with benzene. The benzene solution is dried, and the benzene is evaporated to afford the crude product, which is purified by recrystallization or distillation. 

Reduction of unsaturated carbonyl compounds to the saturated carbonyl is achieved readily and in high yield. Over palladium the reduction will come to a near halt except under vigorous conditions (73). If an aryl carbonyl compound, or a vinylogous aryl carbonyl, such as in cinnamaldehyde is employed, some reduction of the carbonyl may occur as well. Carbonyl reduction can be diminished or stopped completely by addition of small amounts of potassium acetate (i5) to palladium catalysts. Other effective inhibitors are ferrous salts, such asferroussulfate, at a level of about one atom of iron per atom of palladium. The ferrous salt can be simply added to the hydrogenation solution (94). Homogeneous catalysts are not very effective in hydrogenation of unsaturated aldehydes because of the tendencies of these catalysts to promote decarbonylation. 

The tosylhydrazone is prepared from the carbonyl compound and then reduced with lithium aluminium hydride, sodium borohydride or potassium borohydride. In this way D-glucose tosylhydrazone was converted into crystalline 1-deoxyglucitol by reduction with potassium borohydride... 

In the condensation reaction between chloro- and bromo-methyl aryl sulfones and carbonyl compounds, a-sulfonyloxiranes were obtained. In this condensation reaction, bases such as potassium t-butoxides372, NaH373 and aqueous concentrated hydroxide with benzyltriethylammonium chloride under two-phase condensation were used374. In the reaction with aldehydes only the trans-epoxide isomers resulted, whereas lith-iofluoromethyl phenyl sulfone 289375 and 291376 were found to add to aldehydes affording /J-hydroxysulfones 290 and 292, respectively. 

Racemic hydantoins result from the reaction of carbonyl compounds with potassium cyanide and ammonium carbonate or the reaction of the corresponding cyanohydrins with ammonium carbonate (Bucherer-Bergs reaction). Hydantoins racemize readily under basic conditions or in the presence of hydantoin racemase, thus allowing DKR (Figure 6.43). Hydantoinases (EC 3.5.2.2), either isolated enzymes or whole microorganisms, catalyze the hydrolysis of five-substituted... 

The regeneration of carbonyl compounds from 1,3-dithianes can be achieved using potassium hydrogen persulfate, Oxone , supported on wet alumina <96SL767> and by periodic acid under non-aqueous conditions <96TL4331>. The deprotection of benzyl substituted 1,3-dithianes can be achieved using the one electron oxidant [Fe(phen)3](PF6)3 <96SL315>. 

To mention a few synthetic appHcations of trialkylsilanols, trimethylsilanol 4 adds readily to 2-chloroacrylonitrile in diethyl ether in the presence of triethylamine as triethylammonium trimethylsilanolate followed by ehmination of triethylamine hydrochloride to give 99 [32] (cf. discussion of the strongly nucleophihc properties of ammonium trimethylsilanolate 155 in Section 4.2.1). The stable potassium trimethylsilanolate 97 has also been used for the saponification of esters (Section 4.7). Dimethylphenylsilanol 100 adds readily to a,y9-unsaturated carbonyl compounds such as methyl vinyl ketone 764 in the presence of Pd(OAc)2 in a Heck-Suzuki-type reaction to give the sihcon-free /9-phenylmethylvinylketone 101 [33]. 

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

Diazonium salts react with bis(methylsulfonyl) methane (107) (X = S02CH3) to yield a 1,3-diaryl tetrazolinone (111). The reaction proceeds through an azo (108) and a tetrazene (109) intermediate, followed by hydrolysis under the alkaline conditions of the reaction to the carbonyl compound (110). An unexplained oxidation leads to the 1,3-diaryl tetrazolinone (111) either directly or through the intermediate 110a (Scheme 15).18,35 A similar reaction occurs between a diazonium salt and the potassium salt of phenyl hydrazonomethane disulfonic acid (Scheme 15).175... 

A second example of aldolization (Eq. 42) is the dry reaction of ferrocene carbal-dehyde with carbonyl compounds in the presence of potassium hydroxide, and Aliquat as catalyst [63]. Reactions which are too slow at room temperature are efficiently accelerated by use of microwaves, giving good yields within a few minutes. 

The potassium cyanide complex of 18-crown-6 in benzene or acetonitrile undergoes Michael addition to unsaturated carbonyl compounds (Liotta et al., 1977). In the presence of acetone cyanohydrin, the catalytic (i.e. catalytic in potassium cyanide and crown ether) cycle for hydrocyanation shown in (21)... 

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