Ketones, benzyl phenyl synthesis

Ketones are oxidatively cleaved by Cr(VI) or Mn(VII) reagents. The reaction is sometimes of utility in the synthesis of difunctional molecules by ring cleavage. The mechanism for both reagents is believed to involve an enol intermediate.206 A study involving both kinetic data and quantitative product studies has permitted a fairly complete description of the Cr(VI) oxidation of benzyl phenyl ketone.207 The products include both oxidative-cleavage products and benzil, 7, which results from oxidation a to the carbonyl. In addition, the dimeric product 8, which is suggestive of radical intermediates, is formed under some conditions. 

A dithiane synthesis can convert an aldehyde to a ketone. The aldehyde is first converted to its dithiane derivative, which is deprotonated and alkylated. A mercuric chloride-assisted hydrolysis gives the ketone. Show how this technique might be used to convert benzaldehyde to benzyl phenyl ketone. 

As long as the nucleophilic partner is substituted with electron-donating substituents, the Houben-Hoesch reaction has broad scope. This is most directly illustrated by the work of Parmar and co-workers who used Houben-Hoesch conditions for the synthesis of a large number of benzyl phenyl ketones. ... 

The most unexpected by-product of the reaction in this case is 2,3,6-triphenylpyridine. Probably, benzyl phenyl ketone (the usual product of partial deoximation of oximes in the conditions for synthesis of pyrroles) condenses with acetaldehyde (product of acetylene hydration in superbase media [105], Equation 1, Scheme 1.166) to form an equilibrium mixture of ethylenic ketones I and J (Equation 2). The ketone J reacts with benzylamine to close 2,3,6-triphenyltetrahydropyridine cycle K. The latter aromatizes to the pyridine (Equation 3). 

Butylation of phenylacetonitrile with aqueous NaOH, as shown in Scheme 25, proceeds faster by use of high DF (>0.5) anion exchange resins.The strongly alkaline conditions degrade the quaternary ammonium ions of the catalyst. Catalyst (64) (1% DVB) is active for alkylation of phenylacetonitrile and benzyl phenyl ketone, and for Williamson ether synthesis, and it is much more stable in base than AERs. AERs in OH form are catalysts for dichlorocyclopropane syntheses from alkenes, chloroform and solid sodium hydroxide, and for dehydration of amides to nitriles. AERs in the appropriate hydroxide, acetate, or cyanide form are catalysts for aldol condensations, Michael reactions, Knoevenagel condensations, cyanoethylations and cyanohydrin syntheses. " ... 

Conversion of sulfones such as 1955 into their a-sulfonyl anions by treatment with n-BuIi at -78°C in THF then addition of bis(trimethylsilyl)peroxide (BTSP) 1949 afford, via intermediates such as 1956, aldehydes or ketones such as cyclohexanone and HMDSO 7 [146]. This reaction has subsequently been applied to the synthesis of aldehydes [147]. After hthiation with -BuLi thioethers such as phenyl benzyl sulfide 1957 react with BTSP 1949 to give mixtures of the O-silyl 1958 and C-silyl 1959 products [148]. On treatment with -BuLi at -30°C the a,a-bis-(trimethylsilyl)dimethylsulfide 1960 is, hkewise, converted into its anion, which reacts with 1949 to give the a-trimethylsilyloxy sulfide 1961 and MesSiOLi 98 [149] (Scheme 12.41). 

The same one-carbon unit has been employed in a convenient isoflavone synthesis from deoxybenzoins (76S326). Other methods of ring closure of phenyl benzyl ketones to this heterocycle have been reviewed (B-62MI22400) and include triethyl orthoformate (56PIA(A)(44)36), zinc cyanide (58CB2858), ethyl formate (80BCJ831) and ethoxalyl chloride (70JCS(C)1219). 

Iodine-catalysed hydroperoxidation of cyclic and acyclic ketones with aqueous hydrogen peroxide in acetonitrile is an efficient and eco-friendly method for the synthesis of gem -dihydroperoxides and the reaction is conducted in a neutral medium with a readily available low-cost oxidant and catalyst.218 Aryl benzyl selenoxides, particularly benzyl 3,5-bis(trifluoromethyl)phenyl selenoxide, are excellent catalysts for the epoxidation of alkenes and Baeyer-Villiger oxidation of aldehydes and ketones with hydrogen peroxide.219 Efficient, eco-friendly, and selective oxidation of secondary alcohols is achieved with hydrogen peroxide using aqueous hydrogen bromide as a catalyst. Other peroxides such as i-butyl hydroperoxide (TBHP), sodium... 

One known application of AP-methy1ani1inomethy1 ketones is their use in the Bischler indole synthesisJ4 We have found that the a-aminomethyldiphenylphosphine oxides with R3= phenyl and R4= methyl or benzyl, are excellent reagents for the synthesis of 3-substitu-... 

An acceptable method is to oxidize methyl benzyl carbinol (l-phenyl-2-propanol) to phenylacetone (methyl benzyl ketone) with chrome oxide (CrO3) in pyridine solvent. The problem with this is that methyl benzyl carbinol is not commercially available, and so must be made from benzyl chloride grignard reagent and acetaldehyde. This grignard works well, although there can be a problem getting unreacted benzyl chloride out of the product. Their boiling points are very close, so distillation does not separate them completely. But the real question is Why make the synthesis of phenylacetone a two-step process when it can be done with one reaction ... 

Thus, a short-range strategy for the synthesis of 4-hydroxy-l-phenyl-pentanone-2 (I) will lead to the two carbonyl compounds methyl benzyl ketone and acetaldehyde as synthesis precursors (Figure 1). Having reached this conclusion it is absolutely necessary to consider whether those two precursors will react by the anticipated aldol condensation to the target compound (I). A closer inspection based on insight into chemical reactivity has to decide that this reaction will not proceed unequivocally to the desired product (I). Rather, a mixture of compounds will be obtained including the... 

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