Arylations potassium acetate

Reduction of unsaturated carbonyl compounds to the saturated carbonyl is achieved readily and in high yield. Over palladium the reduction will come to a near halt except under vigorous conditions (73). If an aryl carbonyl compound, or a vinylogous aryl carbonyl, such as in cinnamaldehyde is employed, some reduction of the carbonyl may occur as well. Carbonyl reduction can be diminished or stopped completely by addition of small amounts of potassium acetate (i5) to palladium catalysts. Other effective inhibitors are ferrous salts, such asferroussulfate, at a level of about one atom of iron per atom of palladium. The ferrous salt can be simply added to the hydrogenation solution (94). Homogeneous catalysts are not very effective in hydrogenation of unsaturated aldehydes because of the tendencies of these catalysts to promote decarbonylation. 

On the other hand, Mn02 oxidation of lactam 30 or arylation of secondary lactam 32 with bromobenzene using Cu powder and potassium acetate both led to anxiolytic triflubazam (31). ... 

The condensation of furo[3,2- ]pyrrole-type aldehydes 8g and 265-267 with hippuric acid was carried out in dry acetic anhydride catalyzed by potassium acetate as is shown in Scheme 26. The product methyl and ethyl 2-[( )-(5-oxo-2-phenyl-l,3-oxazol-5(4//)-ylidene)methyl]furo[3,2- ]pyrrol-5-carboxylates 268a-d were obtained. The course of the reaction was compared with the reaction of 5-arylated furan-2-carbaldehydes with hippuric acid. It was found that the carbonyl group attached at G-2 of the fused system 8 is less reactive than the carbonyl group in 5-arylated furan-2-carbaldehydes in this reaction <2004MOL11>. The configuration of the carbon-carbon double bond was determined using two-dimensional (2-D) NMR spectroscopic measurements and confirmed the (E) configuration of the products. 

Benzocoumarins (405) result from the dehydrogenation of the corresponding dihydrocoumarins by palladium-charcoal at 300 °C in the absence of solvent (73CB62), whilst 4-aryl-3,4-dihydrocoumarins are converted to the coumarins in diphenyl ether (72IJC32). This latter conversion also occurs under milder conditions using iodine and potassium acetate in acetic acid (73AJC899). 

Disubstituted bicyclo 2.2.1 heptanes.2i Bicyclo[2.2.1]heptene is converted into 2,3-disubstituted derivatives when treated with an aryl or vinyl bromide and an alkyne in the presence of potassium acetate (1 equiv.) and a catalytic amount of Pd[P(C6H5)3LP Example ... 

Fig. 9.36. Enantioscparation of a-aryl propionic acids on 1-allyl-tcrguride-ba.scd WAX type CSP (a) fenoprofen. (b) flobufen. (c) naproxen, and (d) ketoprofen. Exp. cond., 20 mM potassium acetate (pH 3.6)-ttcetonitrile (50 50, v/v( How rate. I.O ml/min detectum. 255 nm (reprinted with permission from Ref. 1.3971).

The reaction can be made catalytic in Pd(II) by using aryl halides as the source of aromatics. The first report of this reaction used phenyl iodide in the presence of potassium acetate (193) ... 

One of the major fields of isocyanate catalysis is pol3mierization. The formation of cyclic dimers and trimers from aryl isocyanates was established over 100 years ago by Hofmann (8). This early work has been reviewed by Saunders (1). Dimers are formed by aryl isocyanates at room temperature in the presence of certain amines or phosphines. Trimeriza-tion occurs in the presence of bases such as potassium acetate. Linear polymerization has been recently reported by Shashoua and co-workers at lower temperatures in polar solvents with an anionic catalyst such as metallic sodium (9, 10). 

The total synthesis of the proteasome inhibitor cyclic peptide TMC-95A was accomplished by. S.J. Danishefsky and co-workers. The biaryl linkage in the natural product was constructed by a Suzuki cross-coupling between an aryl iodide and an arylboronic ester derived from L-tyrosine. The required arylboronic pinacolate substrate was prepared using the Miyaura boration. The aryl iodide was exposed to b/s(pinacolato)diboron in the presence of a palladium catalyst and potassium acetate in DMSO. The coupling proceeded in high yield and no symmetrical biaryl by-product was observed. 

Since the pioneering work by Beletskaya and co-workers [8] the intra- and (more commonly) intermolecular arylation of alkenes has been shown to proceed very smoothly in aqueous medium in the presence of palladium acetate. At the beginning, the methodology seemed to be limited to aryl iodides under a strong influence of the base it was shown that the presence of potassium acetate instead of carbonate yielded lower reaction temperatures and higher rates (Eq. 4). 

CMseH reamuKements. Karanewsky and Kishi have reported that the BOnnal Claisen rearrangement of allyl aryl ethers can be effected in acetic anhydride and sodium or potassium acetate (130-200 ). 

Potassium acetate, phase-transferred by 18-crown-6 from the solid into nonpolar solvents, catalyses the formation from arene diazonium tetrafluoroborates of aryl radicals (Scheme 53),-which in aromatic solvents couple with the solvent to... 

These pioneering studies by Heck have opened the way to a new reaction later called the Mizoroki-Heck reaction (Scheme 1.1). In 1971, Mizoroki et al. reported preliminary results on the PdCh-catalysed arylation of alkenes by iodobenzene in the presence of potassium acetate as base (Scheme 1.5) [4]. No new contribution to the mechanism was proposed, except that palladium particles, formed in situ in the reaction or deliberately added, were suggested to be the active catalyst [4]. 

The Goldberg catalysed Y-arylation of amides gives low yields and requires drastic reaction conditions, but the use of silica-supported copper improves reaction yields. The pyrazolodiazepin system has been A -hetero-arylated in this way using potassium acetate as a base (e.g. equation 4.8) [52]. 

The a-keto amides are less susceptible to hydrolysis and preparation of a-keto esters and acids are preferable for synthesizing various derivatives thereof. Various aryl iodides and bromides can be converted into a-keto esters on reactions with alcohols and carbon monoxide in the presence of a base such as tertiary amines or potassium acetate with catalytic amounts of tertiary phosphine-coordinated palladium complexes (Eq. 11).[42]-[46] jjjgjj yields of a-keto esters can be achieved only when iodide substrates are used. Double carbonylation of aryl bromides to a-keto esters can be accomplished with difficulty at much slower rates. Alkyl and benzyl iodides give no double carbonylation products. 

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