Pinacolone potassium

Examples in which heterocyclic haloarenes have been used include the photostimulated reactions of 2-chlorothiazole, 2-chloro-4-methylthiazole and 2-chloro-5-methylthiazole with pinacolone potassium enolate which lead to the formation of mono- and bis-2-thia-zolyl ketones672 and a study of the reactions of 3-halo-2-amino derivatives of benzo[ ]thio-phene with the potassium salts of acetophenone, pinacolone and cyclohexanone which indicated that, under S l conditions, mainly reduction products were formed673. 

Photo-stimulated reactions of di halopyridines with pinacolone potassium enolate in liquid ammonia lead to facile replacement of both halogens via a modified Sr I mechanism. The potassium salt of phenylacetonitrile reacts with 2,6-dibromopyridine (182) under similar conditions to give a mixture of mono- and disubstituted products 183 and 184 (83JOC1180). The photo-stimulated reaction of 2-bromopyridine (185) and potassioacetonitrile in... 

The photostimulated reactions of the isomeric dihalo-pyridines with pinacolone potassium enolate (Me CC0CH2 K+) in liquid ammonia lead to the facile replacement of both halogens parallel reactions with the potassium salts of phenylacetonitrile and -ethylphenylacetonitrile afford mixtures of mono- and di-substituted products. These displacements occur by S fjl-type mechanisms.5 ... 

Similar stereochemical results were obtained from the addition of the potassium and lithium ions of ethyl acetate, /V,V-dimethylacetamide, acetonitrile, acetophenone and pinacolone to 3-(/erf-butyldimethylsilyloxy)-T-phenylsulfonyl-1-cyclohexene followed by protonation or methylation of the resulting sulfonyl carbanion intermediates7. 

Potassium or lithium derivatives of ethyl acetate, dimethyl acetamide, acetonitrile, acetophenone, pinacolone and (trimethylsilyl)acetylene are known to undergo conjugate addition to 3-(t-butyldimethylsiloxy)-1 -cyclohexenyl t-butyl sulfone 328. The resulting a-sulfonyl carbanions 329 can be trapped stereospecifically by electrophiles such as water and methyl iodide417. When the nucleophile was an sp3-hybridized primary anion (Nu = CH2Y), the resulting product was mainly 330, while in the reaction with (trimethylsilyl)acetylide anion the main product was 331. 

Tetrahydrofuran (THF) and ether were distilled from sodium benzophenone ketyl. Pentane was distilled from lithium aluminum hydride and stored in bottles under a positive pressure of nitrogen. Pinacolone was distilled from potassium carbonate prior to use, bp 106°C (760 mm). 

The reactions of 1,3-dihaloadamantanes with various carbanions in DMSO have been studied.18 For example, potassium enolates of acetophenone and pinacolone and the anion of nitromethane react with 1,3-diiodoadamantane (19) under photo-stimulation a free-radical chain process forms a 1-iodo monosubstitution product (20) as an intermediate, which undergoes concerted fragmentation to yield derivatives of 7-methylidenebicyclo[3.3.1]nonene (21). These and other results were interpreted in terms of the Srn1 mechanism. The work has been extended to the reactions of 1- and 2-halo- and 1,2-dichloro-adamantanes, examples of the SrnI mechanism again being found.19... 

Photostimulated, S r k 1 reactions of carbanion nucleophiles in DMSO have been used to advantage in C—C bond formation (Scheme 1).25-27 Thus, good yields of substitution products have been obtained from neopentyl iodide on reaction with enolates of acetophenone and anthrone, but not with the conjugate base of acetone or nitromethane (unless used in conjunction, whereby the former acts as an entrainment agent).25 1,3-Diiodoadamantane forms an intermediate 1-iodo mono substitution product on reaction with potassium enolates of acetophenone and pinacolone and with the anion of nitromethane subsequent fragmentation of the intermediate gives derivatives of 7-methylidenebicyclo[3.3.1]nonene. Reactions of 1,3-dibromo- and 1-bromo-3-chloro-adamantane are less effective.26... 

Iodobenzenesulfonamide (32) undergoes photostimulated SRN1 reactions in liquid ammonia, with the potassium enolates derived from acetone, pinacolone, 3-methyl-2-butanone, cyclopentanone, cyclohexanone and cyclooctanone, to give fair to good yields of 2H-l,2-benzothiazine-l, 1-dioxides (Scheme 10.59) [73],... 

Seebach, Dunitz and cowoikers fust described the THF-solvated tetrameric aggregates obtained from THF solutions of 3,3-dimethyl-2-butanone (pinacolone) and cyclopentanone lithium enolates. These are represented as (137). The pinacolone enolate also crystallizes as the unsolvated hexamer (138) from hydrocarbon solution, but this hexamer rearranges instantaneously to the tetramer (137) in the presence of THF. Williard and Carpenter completed the characterization of both the Na+ and the K+ pinacolone enolates.Quite unexpectedly the Na pinacolone enolate is obtained from hydrocarbon/THF solutions as the tetramer (139) with solvation of the Na atoms by unenolized ketone instead of by THF. Hie potassium pinacolone enolate is a hexameric THF solvate depicted as (140) and described as a hexagonal prism. A molecular model of (140) reveals slight chair-like distortions of the hexagonal faces in (140) so that the solvating THF molecules nicely fit into the holes between the pinacolone residues. 

---