Alumina-supported potassium fluoride

The same authors (77) also investigated the Michael addition of nitromethane to a,/l-unsaturated carbonyl compounds such as methyl crotonate, 3-buten-2-one, 2-cyclohexen-l-one, and crotonaldehyde in the presence of various solid base catalysts (alumina-supported potassium fluoride and hydroxide, alkaline earth metal oxides, and lanthanum oxide). The reactions were carried out at 273 or 323 K the results show that SrO, BaO, and La203 exhibited practically no activity for any Michael additions, whereas MgO and CaO exhibited no activity for the reaction of methyl crotonate and 3-buten-2-one, but low activities for 2-cyclohexen-l-one and crotonaldehyde. The most active catalysts were KF/alumina and KOH/alumina for all of the Michael additions tested. 

Nitroalkanes282 288 as well as alkyl sulfones283 288 can serve as useful and general alkyli-dene transfer reagents for highly activated Michael acceptors such as alkylidenemalonic esters (equation 131), Alumina-supported potassium fluoride is an effective reagent for the reaction of nitroalkanes282. The alkylidene transfer from sulfones may be promoted by Ni(acac)2289. 

Melot, J.-M., Texier-Boullet, F., and Foucaud, A., Cyclopropanation of electrophilic alkenes with nitroalkanes in the presence of alumina-supported potassium fluoride. Synthesis, 364, 1987. 

The preparation of 2-nitro alcohols was also achieved by reaction of equimolar amounts of nitroal-kanes and aldehydes in the presence of alumina-supported potassium fluoride without solvent (equation 12). A peculiar feature of diis method were reactions performed with aromatic aldehydes, such as benz-aldehyde and furaldehyde, which allowed preparation of the corresponding 2-nitro alcohols without dehydration of these into nitroalkenes, as observed when nitroaldol reactions were performed with organic bases in homogeneous medium or with alumina alone. 

A series of nitrocyclohexanol derivatives has been synthesized by using MW irradiation starting from nitromethane and unsaturated ketones in the presence of alumina-supported potassium fluoride under solvent-free conditions (Scheme 8.34). The reaction involves a double and diastereoselective Michael addition followed by ring closure [102]. 

Ylide generation on alumina or potassium fluoride supported on alumina is of interest since the use of a solvent is unnecessary. ... 

A recent publication by the group of Barbarella has disclosed the rapid preparation of poorly soluble unsubstituted and modified a-quinque- and sexithiophenes by the extensive use of bromination/iodination steps and microwave-assisted Suzuki and Sonogashira cross-couplings (Scheme 6.16) [42]. Suzuki reactions were either carried out under solvent-free conditions on a strongly basic potassium fluoride/ alumina support for the synthesis of soluble oligothiophenes, or in solution phase for the preparation of the rather insoluble a-quinque- and sexithiophenes. In both cases, 5 mol% of [l,l -bis(diphenylphosphino)ferrocene]dichloropalladium(II)... 

V-Benzoyl-TV, TV -dialkylthioureas have been prepared under microwave irradiation using potassium fluoride impregnated on alumina as support. Reaction... 

Lately, a number of papers have dealt with microwave-assisted reactions on palladium-doped A1203. Villemin reported on Stifle, Suzuki, Heck and Trost—Tsuji reactions where potassium fluoride on alumina was used as the base26. The reactions were carried out without solvent or stabilising phosphine ligands in single-mode reactors. The Stifle reactions were noteworthy as the toxic organotin residue remained adsorbed on the solid support, thus allowing a simplified work-up procedure for the otherwise unpleasant, and toxic, stannous by-products. Both the Stifle and the Suzuki reactions could be performed under air. Furthermore, it was noted that with experiments where the... 

In a related transformation, cyclopropanes 7 were obtained from active methylene compounds and electron-deficient alkenes by the action of iodine and potassium fluoride supported on solid alumina. 

By employing arylsulfonyl groups as suitable leaving groups, a highly stabilised carbocation could be generated using potassium fluoride supported on alumina, which then allowed for easy interception by the thus-formed nucleophilie enamine intermediate from the aldehyde and L-proline (Scheme 5.24). 

The use of neutral alumina can lead to multiple addition reactions, but basic alumina gives clean reactions [146]. There are many examples of the use of potassium fluoride supported on alumina being used as a catalyst for Michael additions [125, 147]. 

The insertion reaction between an isocyanide and a sulfenyl chloride generates an intermediate (e.g. equation 4.42), which can undergo 1,3-cycloaddition reactions with electron-deficient species to form pyrroles and pyrrolines. Potassium fluoride supported on alumina is a mild basic catalyst for this process [161]. 

Supported reagents which can perform partial oxidations have been reported for example, the solid base KF-alumina (potassium fluoride supported on alumina) has been found to oxidise fluorene to fluorenone very effectively (Figure 16.22) [27]. 

Jai)anese chemists have demonstrated the utility of alumina coated with potassium fluoride as ua efficient solid support in the synthesis of all-oxygen cro m ethers [5] Recently, we found this method useful in the... 

The yield for and jS increases in passing from LiF to KF. This fact can be associated with increasing basicity of the solid supports not with an appreciable template effect for which the maximum yield should be observed when NaF on alumina was employed. Potassium fluoride on alumina turned out to be the most efficient in the synthesis of... 

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