Symmetrical diaryl ketone

Moreover, reaction time was reduced from hours to minutes or even seconds. Indeed, the carbonylation of aryl halides 335 was completed in 10 s to give symmetrical diaryl ketones 336 in excellent yields (Equation (31)). The process optimization to reduce the amount of catalyst disclosed the fact that this carbonylation reaction followed a radical pathway, initiated by the homolytic cleavage of Co2(CO)8 into -00(00)4. It also appeared that the amount of the Oo catalyst had a direct correlation with the internal temperature reached during the reaction. These findings are critical for the development of extremely fast synthesis using carbonylations. 

Symmetrical diaryl ketones are obtainable by a novel method of transcarbonyla-tion (Fuson. When duroic acid is heated with m-xylene in PPA at 78° for 4.5... 

More recentiy, a rhodium-catalyzed carbonylation of arylzinc compounds was developed by Takagi [117]. In the presence of an Rh-dppf catalyst under 1 bar of CO using 1,2-dibromoethane as the oxidant, carbonylative homo-coupling of arylzinc compounds was achieved, affording symmetrical diaryl ketones in good yields (Scheme 8.33). Under similar conditions, Pd or Ni catalysts induced oxidative homo-coupling of zinc reagents to yield diaryls instead. 

The Pd-catalyzed formation of symmetrical diaryl ketones from arylmercuric salts was first reported by R. F. Heck. The reaction of phenylmercuric chloride with carbon monoxide... 

Arylboronic acids react with carbon monoxide in methanol in the presence of a catalytic amount of Pd(PPh3)4 to give symmetrical diaryl ketones as the major products together with methyl benzoates as the side products (Scheme 28). ... 

Typical procedure. Symmetrical diaryl ketone [946] In a 100-mL round-bottomed flask with a side-arm, oxalyl chloride (1.05 mL, 12 mmol) was added dropwise over a period of 5 min to a solution of p-xylene (1.23 mL, 10 mmol) in dichloromethane (50 mL) at 5 °C. Aluminum chloride (1.33 g, 10 mmol) was then added portion-wise over 5 min to give a yellow suspension. The reaction mixture was allowed to warm to room temperature and stirred for 1 h, during which time dissolution of the solid and gas evolution were observed. A second equivalent of p-xylene (1.23 mL, 10 mmol) was then added dropwise over a period of 5 min, and the reaction mixture was stirred for 13 h at room temperature. It was then chilled in an ice/ water bath, and water (25 mL) was added dropwise over a period of 10 min. The layers were separated, and the aqueous layer was extracted twice with dichloro-... 

A new ketone synthesis has been achieved by using the reaction of organo-mercuric halides and dicobalt octacarbonyl in tetrahydrofuran. This method is particularly useful for the preparation of symmetrical diaryl ketones (Seyferth and Spohn, 1968, 1969). The following mechanism has been postulated (Scheme 10). 

Aliphatic nitriles react slowly with phenols and phenyl ethers in the presence of trifluoromethanesulphonic acid to give ketones after hydrolysis, in a variation of the Houben-Hoesch reaction. The crystalline complex of copper(i) triflate and benzene induces the acylation of aromatic substrates with selenol esters, affording a transition-metal mediated version of the Friedel-Crafts reaction. Aromatic carboxylic acids can be converted into symmetrical diaryl ketones in good yield by treatment of their 5-(2-pyridyl)thioesters with bis-(l,5-cyclo-octadiene)nickel [equation (15)]. In contrast to other methods for preparing symmetrical aromatic ketones, this method allows their preparation from a single starting material. 

In 2003, an extremely fast protocol for the cobalt carbonyl mediated formation of symmetric diaryl ketones from aryl halides was disclosed by Larhed and coworkers [38]. Microwave irradiation of aryl iodides and Co2(CO)g in acetonitrile for 10 s or less was enough to produce high yields (57-97%) of symmetric diaryhnethanones (Scheme 4.25). Please note that the Co2(CO)8-mediated chemistry was performed without an additional transition metal catalyst. 

The intermolecular McMurry reaction is first of all a suitable method for the synthesis of symmetrical alkenes. With a mixture of carbonyl compounds as starting material, the yield is often poor. An exception to this being the coupling of diaryl ketones with other carbonyl compounds, where the mixed coupling product can be obtained in good yield. For example benzophenone and acetone (stoichiometric ratio 1 4) are coupled in 94% yield. ... 

The earliest studies on this reaction began with an attempt to generate simple symmetrical pinacols. Reaction of 1 equiv. of ytterbium metal with 2 equiv. of a diaryl ketone in IllF/HMPA provided excellent yields of the corresponding symmetrical pinacols (equation 98). Interestingly, when equimolar quantities of ytterbium metal and benzophenone were employed, the sole product isolated after aqueous work-up was benzhydrol. When D2O was utilized to quench this reaction mixture, C-deuterated benzhy-drol was formed (equation 99). These latter results in cated that a discrete ketone dianionic intermediate was generated in the reaction between ytterbium metal and diaryl ketones. 

R-Y-COCl plays the key role in phosgenation reactions that are of a stepwise nature the major part of these processes is COCl (chlorocarbonyl) transfer to R-Y-H generating chloroformates, carbamoyl chlorides, etc. R-Y-COCl is of limited (low) stability and this is the driving force behind its intermediacy in the synthesis of chlorides and isocyanates under elimination conditions (eliminating CO2 and/or HCl), and also determines the character of a reactive substrate in further nucleophilic substitutions to form symmetrical and unsymmetrical substituted carbonic acid derivatives carbonates, carbamates, ureas) or diaryl ketones. Commonly, chloro-formylation and isocyanate formation are independent of the nature of R. Obviously, the reactivity is very different due to the relative basic/nucleophilic ratio. For example, Ar-Cl cannot be prepared through a chloroformate intermediate nor by direct phosgenation, but the reaction does work well in the aliphatic series. 

The AICI3-mediated chlorocarbonylation of arenes with oxalyl chloride has been used in the preparation of symmetrical and unsymmetrical diaryl ketones 1266 [945, 946],... 

Under Friedel-Crafts conditions (AICI3, CS2), oxalyl chloride reacts with aromatic hydrocarbons to give carbonyl chlorides, which are hydrolyzed by water to give carboxylic acids. The AICI3-mediated chlorocarbonylation of arenes with oxalyl chloride has been used in the preparation of symmetrical and unsymmetrical diaryl ketones [946] (see also Section 4.3.6). 

Treatment of 2-benzylideneamino-l-phenylvinyl benzoate (47) with sodium methoxide produced one major product which was assigned as 2,5-dibenzoyI-3,6-diphenyl-1,4-dihydropyrazine (48) (1585). Dimerization of a series of a-arylamino ketones (49) in toluene with p-toluenesulfonic acid gave the symmetrical 1,4-diaryl-1,4-dihydropyrazine (50), not the corresponding l,4-diaryl-l,4-dihydropyrazines (51) or l-aryl-l,2-dihydropyrazines (52). Thus w-(4-chloroanilino)acetophenone gave 1,4-bis(p-chlorophenyl)-2,6-diphenyl-1,4-dihydropyrazine (1546). 

Fluorenone oxime was recovered unchanged after being heated with PPA at 120°, but at 180° it was rearranged in almost quantitative yield (Conley )- Conley found PPA to be a superior solvent-catalyst for the Schmidt rearrangement. He added sodium azide in portions to a mixture of a diaryl, aryl-alkyl, symmetrical or unsymmetrical ketones with 15-20 parts of PPA at a temperature in the range 25-75° until evolution of nitrogen ceased, and obtained amides in yields mainly of 80-90%. Doorenbos and Wu studied the conversion of cholestanone and... 

Nucleophilic displacement of chlorine, in a stepwise manner, from cyanuric chloride leads to triazines with heteroatom substituents (see Section 6.12.5.2.4) in symmetrical or unsymmetrical substitution patterns. New reactions for introduction of carbon nucleophiles are useful for the preparation of unsymmetrical 2,4,6-trisubstituted 1,3,5-triazines. The reaction of silyl enol ethers with cyanuric chloride replaces only one of the chlorine atoms and the remaining chlorines can be subjected to further nucleophilic substitution, but the ketone produced from the silyl enol ether reaction may need protection or transformation first. Palladium-catalyzed cross-coupling of 2-substituted 4,6-dichloro-l,3,5-triazine with phenylboronic acid gives 2,4-diaryl-6-substituted 1,3,5-triazines <93S33>. Cyanuric fluoride can be used in a similar manner to cyanuric chloride but has the added advantage of the reactions with aromatic amines, which react as carbon nucleophiles. New 2,4,6-trisubstituted 1,3,5-triazines are therefore available with aryl or heteroaryl and fluoro substituents (see Section 6.12.5.2.4). 

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