Potassium alkyl group exchange

Potassium t-butoxide. 13,252-254 15,271 -272 17,289-290 18,296-297 19,273-275 t-Butylesters. By subjecting esters to r-BuOK-r-BuOAc in THF at room temperature, exchange of the alkyl group takes place (10 examples, 88-99%). 

Oxidation of 2-hydroxy-3-alkyl-l,4-quinones with potassium permanganate with shortening of the alkyl side chain by one methylene and the position exchange between hydroxyl and alkyl groups. 

The isoselenazole ring in unsubstituted 3-hydroxy-l-benzo-l,2-selenazole (26) and in its 7-azaanalog (27) exists in nonaromatic amide form such as in 28 or 29 (Scheme 4). The amide proton is easily exchanged, via potassium salt, by alkyl, acyl, or sulfonyl groups. The additional evidence for amide structure is based on spectral data. For example, the amide band nc=0 = 1646 cm 1 in the IR spectrum and the broad singlet at 9.34 ppm in the 11 NMR spectrum were observed for 29 [49-51],... 

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... 

This reaction was initially reported by Finkelstein in 1910. It is a preparation of alkyl iodide from alkyl bromide or chloride with potassium or sodium iodide in acetone. Therefore, this reaction is generally known as the Finkelstein reaction. Occasionally, it is also referred to as the Finkelstein halide exchange, Finkelstein displacement, or Conant-Finkelstein reaction. Mechanistically, this reaction is a simple nucleophilic substitution (often via Sn2), as iodide is a stronger nucleophile than bromide or chloride. The yield of this reaction is very high and can be quantitative if occurs in DMF. It was found that the trifluoromethyl group retards the displacement of bromide when it presents as an a- or /3-substituent but accelerates the reaction as a substituent in an allylic chloride. Under normal conditions, this type of halide displacement does not occur for aryl halides. For dihalides, unsaturated or cyclic compounds may form via carbocation intermediates, which form transient covalent iodides or are reduced directly by iodide to free radicals. However, the aromatic halide exchange reacts smoothly when 10% Cul is present in the reaction... 

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