Potassium fluoride-Alumina

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)... 

Cesium fluoride-Tetraalkoxysilanes, 69 Hexamethylphosphoric triamide, 142 Methyl acrylate, 183 a-Methylbenzylamine, 185 Methyl vinyl ketone, 193 Potassium t-butoxide, 252 Potassium f-butoxide-Xonotlite, 254 Potassium fluoride-Alumina, 254 Tin(II) trifluoromethanesulfonate, 301 Titanium(IV) chloride, 304 Trityl perchlorate, 339 Vinyl(triphenyl)phosphonium bromide, 343... 

Lithium hydride, 165, 240, 257 Methyllithium, 188, 315 Potassium bicarbonate, 253 Potassium carbonate, 233, 254, 322 Potassium carbonate-18-Crown-6, 94 Potassium fluoride-Alumina, 15, 254, 256... 

Phenyl azide-Aluminum chloride, 240 Potassium fluoride-Alumina, 15, 254, 256... 

Kabalka, G.W., Wang, L., Pagni, R.M., Hair, C.M. and Namboodiri, V., Solventless Suzuki coupling reactions on palladium-doped potassium fluoride alumina, Synthesis, 2003, 217-222. 

DEHYDROBROMINATION Lithium chlo-ride-Hexamethylphosphoric triamide. Potassium fluoride-Alumina. 

Aceto(carbonyl)cyclopentadienyl(tri-phenylphosphine)iron. 3-Acylthiazolidine-2-thiones. Bis(cyclopentadienyl)titana-cyclobutanes. Bromomagnesium diisopro-pylamide. Cerium(III) chloride. Dichloro-phenylborane. Dimethylphenylsilyllithium. Ethylene chloroboronate. Ketene bis(trimethylsilyl)ketals. Mandelic acid. Norephedrine. Potassium fluoride-Alumina. (S)-(—)-Proline. Tetra-n-butylam-monium fluoride. Tin(IV) chloride. Tin(II) trifluoromethanesulfonate. Titanium(IV) chloride. Tri-n-butyltin fluoride. Trityl perchlorate. 

A solventless Suzuki coupling reaction has been developed using both thermal and microwave-assisted methods. A potassium fluoride-alumina mixture is utilized along with palladium powder. The KF acts as a base. ... 

Schmittling, E. A., Sawyer, J. S. Synthesis of diaryl ethers, diaryl thioethers, and diarylamines mediated by potassium fluoride-alumina and 18-crown-6. J. Org. Chem. 1993, 58, 3229-3230. 

Dithioacetal Formation. Dithioacetals are prepared from activated methylene compounds with MeSS02Me absorbed on potassium fluoride-alumina (eq 7). Microwave irradiation without solvent provides a powerful activation for this preparation. MeSCl gives only poor yields and MeSSMe does not react under these conditions. ... 

Ort/io-selectivity is generally observed in the reactions of 2,4-dichloro- and 2,4-difluoro-nitrobenzene with alkoxide and thiophenoxide ions [199]. Also in less activated systems, nucleophiles generated from phenols and thiophenols with potassium fluoride-alumina and 18-crown-6-polyether will react in DMSO with cyano- or nitro-substituted fluoro- or chloro-benzenes [200]. Interestingly, the reaction of difluorobenzenes with two diffoent alcohols can occur sequentially. Introduction of the first etho" function deactivates the ring, and use of more forcing conditions allows substitution of the second fluorine [201]. Consecutive displacements of fluorine and nitro groups have been observed in the reaction of ort/io-fluoronitrobenzene with chiral acyl bicyclic lactones in a highly enantioselective synthesis of spirooxindoles [202]. 

Chemicals and reagents were obtained from commercial sources. Solvents were purified by standard techniques to give anhydrous solvents. Phosphorous trichloride, triethylamine, and thionyl chloride were distilled before use. Potassium fluoride, alumina, and sodium iodide were dried by oven before use. Thin layer chromatography (TLC) and column chromatography were performed on silica gel. 

Benzylation of alcohols using Potassium Fluoride-Alumina and benzyl bromide in acetonitrile at room temperature is effective. Silver oxide in DMF is yet another base system. Of particular interest in carbohydrate applications is the reaction of benzyl bromide with carbohydrate derivatives which have been pretreated with tin reagents. Thus it is possible to benzylate an equatorial alcohol in the presence of an axial alcohol (eq 1) and also to selectively benzylate an anomeric hydroxy through Di-n-butyltin Oxide. ... 

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