Acetophenone potassium enolate

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... 

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. 

The potassium enolate is prepared by dropwise addition of 2.4 g (20 mmol) of acetophenone lo a suspension of 0.8 g (20 mmol) of KH in 20 mL of dry THF with vigorous stirring at r.t. under N2 Subsequent addition of 22 mL (22 mmol, 1 M in THF) of Et3B soln at r.t. generates the required borate. cis-5-Phenyharbotnimethyt-i-cyclohexene-l-carboxylic Acid ... 

Potassium enolates of cyclohexanone, acetone, and acetophenone react with 3-iodo-benzo[Z)]thiophene in DMSO in the dark to give the a-heteryl ketones in low yield <92H(34)I039>. The initiation step in the radical chain process is probably an electron transfer from the enolate to the 3-iodobenzo[i>]thiophene. The low yields of the products are partly due to competing ionic reactions. 

Transmetallation is also a highly important concept to obtain enolates of the late transition metals rhodium, palladium, and nickel, not only for their preparation and isolation, but also for their intermediate generation in catalytic cycles. When 2 equiv. of the potassium enolates 166 of acetophenone and pinacolone... 

The leaving group in the alkylating reagent has a major effect on whether C- or O-alkylation occurs. In the case of the lithium enolate of acetophenone, for example, C-alkylation is predominant with methyl iodide, but C- and O-alkylation occur to approximately equal extents with dimethyl sulfate. The C- versus O-alkylation ratio has also been studied for the potassium salt of ethyl acetoacetate as a function of both solvent and leaving group. ... 

The silyl enol ether may be obtained from the Fluka Chemical Corp., 255 Oser Avenue, Hauppauge, NY 11788. Alternatively, it may be prepared by the following modification of the procedure of Walshe and co-workers.2 The Walshe procedure is followed exactly with 36 g (0.30 mol) of acetophenone, 41.4 g (0.41 mol) of tri ethyl amine, 43.2 g (0.40 mol) of chlorotri-methylsilane, 60 g (0.40 mol) of sodium iodide, and 350 nt of acetonitrile. After extraction, the organic layer is dried over potassium carbonate and then concentrated with a rotary evaporator under reduced pressure. The crude product is a mixture of 97% of the desired silyl enol ether and 3% of acetophenone, as shown by gas chromatography. The crude product is distilled in a Claisen flask at a pressure of about 40 mm. After a small forerun (ca. 3... 

A systematic study of the reductive alkylation of acetophenones revealed that the desired transformation (Scheme 30) required a careful selection of reagents and conditions. The best results were obtained from reduction by potassium in ammonia at -78 °C, with t-butyl alcohol as the proton source. Exchange of the potassium counterion of the enolate (152 M = K) for lithium then ensured regioselective alkylation at C-1 to give (153) in 80-90% yields (Scheme 30). Metals other than potassium as the reductant led to undesirable side reactions with the carbonyl group, which included simple reduction to the methylcar-binol and ethylbenzene (lithium or sodium), while the absence of a proton source or presence of a strong... 

Considerable interest has been expressed in the development of direct methods for the synthesis of a-hydroxy ketones using nontoxic hypervalent iodine reagents and which involve the foUowing methods reaction of a ketone with iodobenzene diacetate in the presence of potassium hydroxide in methanol and then hydrolysis of the dimethylacetals oxidation of the enol sUyl ether of acetophenone using the s) tem iodosobenzene/boron trifluoride efherate/water in methylene chloride at—40°C and reaction of ketones with [fcis(trifluoroacetoxy)]iodobenzene and trifluoroacetic acid in acetonitrile-water under acidic conditions. "... 

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