Arylalkyl ketone

The Bogert synthesis of 2,4-diarylthiophenes consisting of the reaction of sulfur with the anils of arylalkyl ketones, has been shown to lead to a mixture of 2,4- and 2,5-disubstituted thiophenes. ... 

The hydrosilylation of carbonyl compounds by EtjSiH catalysed by the copper NHC complexes 65 and 66-67 constitutes a convenient method for the direct synthesis of silyl-protected alcohols (silyl ethers). The catalysts can be generated in situ from the corresponding imidazolium salts, base and CuCl or [Cu(MeCN) ]X", respectively. The catalytic reactions usually occur at room tanperature in THE with very good conversions and exhibit good functional group tolerance. Complex 66, which is more active than 65, allows the reactions to be run under lower silane loadings and is preferred for the hydrosilylation of hindered ketones. The wide scope of application of the copper catalyst [dialkyl-, arylalkyl-ketones, aldehydes (even enoUsable) and esters] is evident from some examples compiled in Table 2.3 [51-53],... 

Arylalkyl ketones (80) are reduced to alcohols over the pH range of 7 to 12 (approx.) 73>. The reduction probably involves the following sequence of steps ... 

The easiest substrates to test are acetophenones, as many substituted analogues are commercially available from laboratory suppliers. A large range of results have been reported the best enantiomeric excesses achieved and relevant literature reference are detailed in Tables 35.4 and 35.5. The range of ketones that can be reduced includes substituted diaryl, dialkyl and arylalkyl ketones, alpha-,... 

Based on steady-state and time-resolved emission studies, Scaiano and coworkers have concluded that silicalite (a pentasil zeolite) provides at least two types of sites for guest molecules [234-236], The triplet states of several arylalkyl ketones and diaryl ketones (benzophenone, xanthone, and benzil) have been used as probes. Phosphorescence from each molecule included in silicalite was observed. With the help of time-resolved diffuse reflectance spectroscopy, it has been possible to show that these triplet decays follow complex kinetics and extend over long periods of time. Experiments with benzophenone and arylalkyl ketones demonstrate that some sites are more easily accessed by the small quencher molecule oxygen. Also, diffuse reflectance studies in Na + -X showed that diphenylmethyl radicals in various sites decay over time periods differing by seven orders of magnitude (t varies between 20/is and 30 min) [237]. 

A consequence of the occupation of more than one site in solid inclusion complexes is illustrated with a single example, although many more are available in the literature. Detailed study of arylalkyl ketones included in deoxycolic acid (DCA) channels have been carried out by Lahav, Leiserowitz,... 

Aldehydes and unhindered aliphatic ketones or arylalkyl ketones add hydrogen cyanide to form cyanohydrins (Equation 8.22). As with hydration, the equilib-... 

The allylation of hydrazones derived from arylalkyl ketones [42] and of N-aryl aldimines in DMF at 0 °C [46] have also been reported. 

Traditionally cyanohydrins have been prepared by processes that require the establishment of an equilibrium between a ketone and its corresponding cyanohydrin. For many ketones, especially those that are sterically hindered, the position of the equilibrium is unsatisfactory for the effective synthesis of the cyanohydrin. We describe herein a general method for the synthesis of cyanohydrins which does not depend on an equilibrium process. As a result this synthetic procedure can be used to convert a wide variety of dialkyl, diaryl, and arylalkyl ketones into their corresponding cyanohydrins. In addition to the described conversion of benzophenone into its cyanohydrin, acetophenone, fluorenone, tert-butyl phenyl ketone, and a wide variety of aliphatic ketones have been converted into cyanohydrins by this general procedure (Table... 

IPC)2BC1 (6.64) also transfers 3-hydrogen and librates 1 equiv. of a-pinene. The reagent is best used for the asymmetric reduction of arylalkyl ketones, a-t-alkyl ketones and a-halo ketones. 

Substituted quinazolines 49 are conveniently prepared by the action of formamide on 2-aminophenyl alkyl, aryl, and arylalkyl ketones 48 in the presence of boron trifluoride diethyl ether complex as catalyst.This variation gives good yields and cleaner products than the method- in which formic acid is used as catalyst. 

Numerous ketones serve as substrates for alcohol dehydrogenases. These include alicyclic and arylalkyl ketones [Eq. (14)]. 

As expected, Baeyer-Villiger reactions of simple arylalkyl ketones are oxidised to esters in which aryl migration is observed. Examples are shown in Eq. (31) to (33). 

Thorough kinetics studies of the chlorination of aliphatic, alicyclic, and arylalkyl ketones with CBT were carried out by Indian workers (82PIA921). Kinetic measurements were performed using aqueous acetic acid and the addition of HC104 and NaCl. In the presence of mineral acid the reaction is first order in ketone and acid and zero order in CBT. A large kinetic isotopic effect was observed (for acetone kHlkD = 6.6). Addition of chloride ion causes some changes in the reaction order they become first order in CBT, 0.6 in ketone, and 0.2 in chloride ion. The rate constant for chlorination of substituted acetophenones correlate with a constants for substituents in the aryl ring (p is -0.57). On the basis of these data the mechanism in the absence and in the presence of chloride ion was developed. 

Unsymmetrical derivatives of this ring system have also been prepared in unambiguous fashion by condensation of the arylalkyl ketones 37 with the azo derivatives 36. - ... 

Reduction of the hydroxyimino group with acetylation of the resulting amino group can be effected by zinc dust in the presence of acetic acid and acetic anhydride diethyl (acetylamino)malonate, which is important for amino acid syntheses, has been prepared in this way.97 Zinc dust reduces oximes of diaryl and arylalkyl ketones better in concentrated ammoniacal than in acid solution, giving the amines as very pure free bases whilst hardly any higher alkylated product is formed.98 Aminoacetone," diaminoacetone,100 and 2-afnino-3-pentanone" have been obtained by reducing oximes with tin or tin(n) chloride in alcoholic hydrochloric acid solution. In individual cases oximes have been reduced by sodium dithionite or aluminum amalgam.198 Further, the patent literature contains examples of electrolytic reduction of oximes.198... 

The reaction of either (R)- or (5)-a-methylbenzylamine (364) with sulphuryl chloride gives the (R,R) and (5,5) N,N bis(a-methylbenzyl) sulphamide 365. When 365 is added to LiAlH4 in the presence of A-benzylmethylamine in tetrahydrofuran, it leads to the asymmetric reduction of prochiral ketones 366 (equation 115)363. Optimization of the reaction was carried out with respect to enantioselectivity and reactivity of the reagents. The use of iV-benzylmethylamine as an additive was found to be superior to ethanol. Reaction at — 20 °C gave 87% selectivity with a one-hour reaction time. Both arylalkyl ketones and dialkyl ketones are asymmetrically reduced in the reaction. 

Chromones. 3-Substituted chromones, including isoflavones (3-arylchro-niones), can be prepared in fair to excellent yields by treatment of 2-hydroxy-phcnyl alkyl (arylalkyl) ketones (I) with BF3 etherate (exothermic reaction) in DMF. Metlianesulfonyl chloride in DMF (Vilsmeier reagent) is then added at 52 and (he reaction is warmed on a steam bath (90 minutes). Chromones (2) arc obtained in 65 96% yield. The function of BF , etherate is to deactivate the hydroxylalcd aromatic ring hy complex formation and thus prevent ring lormylalion. 

A report has appeared of the reaction between 4-nitrophenyl azide and some enamines of aliphatic or arylalkyl ketones. Under kinetically controlled conditions the cis-trans equilibrium mixture of enamine (91) gives exclusively the /ran -triazoline (92), but at higher temperatures or in the presence of acid catalysts the /ra/i -isomer epimerizes, giving the cis-trans equilibrium... 

Novel preferential reduction. Diaryl ketones are much more reactive toward Li-N-dihydropyridylaluminum hydride (formula s. 944) than are either dialkyl or arylalkyl ketones. This sequence is in contrast to that found with NaBH4 in isopropanol and appears to be without precedent in nucleophilic addition to carbonyl groups. E. and limitation s. P. T. Lansbury and J. O. Peterson, Am. Soc. 54, 1756 (1962). 

Arylalkyl ketones rearrange on treatment with phosphoryl azides to give the phosphorylated amide of fenvaleric acid (Reaction scheme 191) [526]. 

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