Ketone symmetrical

Also obtained by complete dealkylation of 4,4 -diethoxybenzophenone with hydrobromic acid in boiling acetic acid for 2 days [142], 

Preparation by hydrolysis of 4,4 -dichlorobenzophenone with aqueous sodium hydroxide in the presence of cuprous chloride or cupric chloride in an autoclave at 230-240° for 2 h (95-98%). The same reaction using cuprous oxide at 200° for 2 h gave a 82% yield [310,311 ]. Other methods using copper compounds for hydrolysis of the 4,4 -dichlorobenzophenone in the presence of sodium hydroxide [312,313], for 1 h at 270° in a steel autoclave (98-99%) [314]. 

Preparation by Fries rearrangement of phenyl p-anisate (phaiyl p-methoxybenzoate) with aluminium chloride at 140° (80%) [132] or at 160° [315]. 

Also obtained by reaction of p-hydroxybenzoic acid with phenol, 

Also obtained by treatment of 4,4 -diphenoxybenzophenone with 16.7% sodium hydroxide at 300° for 30 min (57%) [318]. 

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By dropping au aromatic acid either alone or mixed with an aliphatic acid into a tube containing a thoria catalyst deposited on pumice and heated to 400-450°. This method is generally employed for the preparation of mixed aromatic - aliphatic ketones. Excess of the aUphatic acid is usually present since this leads to by-products which are easily separated and also tends to increase the yield of the desired ketone at the expense of the symmetrical ketone of the aromatic acid. Thus —... 

Also due to the high barrier of inversion, optically active oxaziridines are stable and were prepared repeatedly. To avoid additional centres of asymmetry in the molecule, symmetrical ketones were used as starting materials and converted to oxaziridines by optically active peroxyacids via their ketimines (69CC1086, 69JCS(C)2648). In optically active oxaziridines, made from benzophenone, cyclohexanone and adamantanone, the order of magnitude of the inversion barriers was determined by racemization experiments and was found to be identical with former results of NMR study. Inversion barriers of 128-132 kJ moF were found in the A-isopropyl compounds of the ketones mentioned inversion barriers of the A-t-butyl compounds lie markedly lower (104-110 kJ moF ). Thus, the A-t-butyloxaziridine derived from adamantanone loses half of its chirality within 2.3 days at 20 C (73JCS(P2)1575). 

Fc(CO)5] reacts similarly. Aldehydes and ketones can also be obtained from N,N-disubstituted amides, and symmetrical ketones are formed by reaction with CO ... 

The importance of chemical syntheses of a-amino acids on industrial scale is limited by the fact that the standard procedure always yields the racemic mixture (except for the achiral glycine H2N-CH2-COOH and the corresponding amino acid from symmetrical ketones R-CO-R). A subsequent separation of the enantiomers then is a major cost factor. Various methods for the asymmetric synthesis of a-amino acids on laboratory scale have been developed, and among these are asymmetric Strecker syntheses as well. ... 

As a symmetrical ketone, acetone is a reactive compound with many synthetic uses. Among the important chemicals based on acetone are methylisobutyl ketone, methyl methacrylate, ketene, and diacetone alcohol. 

Ketones are inert to most oxidizing agents but undergo a slow cleavage reaction when treated with hot alkaline KMnO The C-C bond next to the carbonyl group is broken, and carboxylic acids are produced. The reaction is useful primarily for symmetrical ketones such as cyclohexanone because product mixtures are formed from unsymmetrical ketones. 

The achiral enolate 1 reacts with symmetrical ketones to provide aldol-type products1. 

The chiral lithium enolate 2 reacts with symmetrical ketones to produce /(,/i-dialkyl-/l-hydroxy-acyl complexes 3 which serve as precursors to oc,/1-unsaturated iron complexes (see Section 1.3.4.2.5.1.1.). 

Aldol reactions of a-substituted iron-acetyl enolates such as 1 generate a stcrcogenic center at the a-carbon, which engenders the possibility of two diastereomeric aldol adducts 2 and 3 on reaction with symmetrical ketones, and the possibility of four diastereomeric aldol adducts 4, 5, 6, and 7 on reaction with aldehydes or unsymmetrical ketones. The following sections describe the asymmetric aldol reactions of chiral enolate species such as 1. 

The lithium enolate 2a (M = Li ) prepared from the iron propanoyl complex 1 reacts with symmetrical ketones to produce the diastercomers 3 and 4 with moderate selectivity for diastereomer 3. The yields of the aldol adducts are poor deprotonation of the substrate ketone is reported to be the dominant reaction pathway45. However, transmetalation of the lithium enolate 2a by treatment with one equivalent of copper cyanide at —40 C generates the copper enolate 2b (M = Cu ) which reacts with symmetrical ketones at — 78 °C to selectively produce diastereomer 3 in good yield. Diastereomeric ratios in excess of 92 8 are reported with efficient stereoselection requiring the addition of exactly one equivalent of copper cyanide at the transmetalation step45. Small amounts of triphcnylphosphane, a common trace impurity remaining from the preparation of these iron-acyl complexes, appear to suppress formation of the copper enolate. Thus, the starting iron complex must be carefully purified. 

Carboxylic acids can be converted to symmetrical ketones by pyrolysis in the presence of thorium oxide. In a mixed reaction, formic acid and another acid heated... 

Symmetrical ketones can be prepared in good yields by the reaction of organo-mercuric halides with dicobalt octacarbonyl in THF, or with nickel carbonyl in DMF or certain other solvents. The R group may be aryl or alkyl. However, when R is alkyl, rearrangements may intervene in the C02(CO)g reaction, though the Ni(CO)4 reaction seems to be free from such rearrangements. Divinylic ketones... 

Non-symmetrical ketones suffer from the fact that the regiochemistry cannot be predicted. Since both adjacent C-C bonds migrate, the yield is decreased. 

Ansuer Disconnection (a) on TM (8) gives symmetrical ketone (10). The alternative disconnection (b) would require bis-Grignard (11) - a doubtful species. 

Suggest a synthesis of symmetrical ketone (1). The symmetry is a help, so disconnect by opening both th nembered rings at once ... 

Disconnection gives dihaloketonc (2) made from (3). This compound is best approached by the strategy we have often used for symmetrical ketones adding an activating group and using a 1,3-dicarbony i disconnection. There is a very similar example on p 329. ... 

The tvans alcohol (47) might be made by reduction of ketone (48). Oxidation of (45) would give (48), but an alternative is to add an activating group and disconnect as a 1,3-dicarbonyl compound - standard strategy ior a symmetrical ketone. 

Lactone (15) can be derived by Baeyer-Villiger oxidation of syrnmetrica) ketone (16) whose further analysis follows the usual strategy for symmetrical ketones,... 

Fischer indole disconnection reveals hydrazine (20) and symmetrical ketone (21) (Chapter T 30) as starting materials. The hydrazine can be made from (22) by nltrosatlon and reduction. 

Small quantities of the symmetrical ketones (CHgigCO and (CHgCHgCHglgCO (di-n-propyl ketone) are formed as by-products these can easily be removed by fractional distillation through an efficient column. An excess of the cheaper reagent, acetic acid, is employed the resulting acetone is readily removed by washing with water and little di-n-propyl ketone is formed under these conditions. 

Section B of the Scheme 9.1 shows several procedures for the synthesis of ketones. Entry 6 is the synthesis of a symmetrical ketone by carbonylation. Entry 7 illustrates the synthesis of an unsymmetrical ketone by the thexylborane method and also demonstrates the use of a functionalized olefin. Entries 8 to 10 illustrate synthesis of ketones by the cyanide-TFAA method. Entry 11 shows the synthesis of a bicyclic ketone involving intramolecular hydroboration of 1,5-cyclooctadiene. Entry 12 is another ring closure, generating a potential steroid precursor. 

Stockman and coworkers [329] developed a straightforward synthesis of a tricyclic compound 2-636 which has some resemblance to the spirocyclic portion of the natural product halichlorine (2-637) [330]. On treatment of the symmetrical ketone 2-633, accessible in five steps from alcohol 2-632, with hydroxylamine hydrochloride the spiro piperidine 2-636 could be obtained in 62% yield (Scheme... 

The methanochromanone 71 is converted with high trans-selectivity into the furo[2,3-fc]chromanone 72 by reaction with symmetric ketones (Scheme 50) <00H(53)657>. 

The direct metallation of jV-BOC piperidine 353a with t-BuLi in presence of TMEDA in THF at low temperature and reaction with a symmetrical ketone directly afforded the five-membered oxazilidinone 353b (Scheme 52) <2001JA315>. 

Carbonylations of organolead triacetates with CO (latm), which proceed in the presence of Pd2(dba)3 and an excess of sodium methoxide to furnish symmetrical ketones, such as compounds 28 and 29, deserve special mention (Equations (12) and (13)).48... 

Alternatively, CO2 can be used as source of CO. Indeed, it is well known that low-valent transition metal complexes can catalyze the chemical or electrochemical reduction of CO2 into CO. This approach was used to generate the mixed nickel complex Ni°bpy(CO)2 by the electrochemical reduction of Nibpy in NMP or DMF in the presence of CO2. The reduced complex can react with alkyl, benzyl, and allylhalides to give the symmetrical ketone along with the regeneration of Nibpy ". A two-step method alternating electroreduction and chemical coupling leading to the ketone has thus been set up (Scheme 9) [126,127]. 

Apart from the electrocarbonylation reactions of organic halides described in Sect. 6, other Ni-catalyzed reactions leading to ketones have been reported. Thus the electroreductive coupling between acylchlorides and alkyl halides, catalyzed by NiBr2bpy leads to unsymmetrical ketones [129]. Recently acylchlorides have been converted to symmetrical ketones in an undivided cell fitted with a nickel or stainless steel anode. In this reaction the active metallic species... 

In 1996 Yang and coworkers reported a series of binaphthyl-derived -symmetric ketones (8) as epoxidation catalysts (a few examples are shown in Fig. 2)[32-34],... 

Fig. 21 Fused ring ketones 26, 55-58 and pseudo C -symmetric ketones 62...

The reduction of aroyl chlorides take a different course in the presence of Ni(ll) salts. Reaction is best effected in an undivided cell with a nickel anode and a nickel foam cathode with acetonitrile containir tetrabutylammonium fluoroborate as electrolyte. Symmetrical ketones are formed [173], Substimted benzoyl chlorides yield the benzophenone in 47-72% yields. Phenacetylchloride also gives the ketone in good yield but in general, alkanoyl chlorides do not react. 

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