Aromatization ketones, cyclic

Refractive index 1.44-1.447 Solubility in solvents chlorinated, aromatic, ketones, cyclic aliphatic, chlorinated aromatic hydrocarbons ... 

Exceptions to this statement have been noted in the case of cyclic aromatic ketones bearing electron-donating groups in ortho and para positions Bhalerao, U.T. Thyagarajan, G. Can. J. Chem., 1968, 46, 3367 Tomita, M. Minami, S. Uyeo, S. J. Chem. Soc. C, 1969, 183. 

No stereoselectivity was observed in the formation of a 1 1 diastereomeric mixture of 2-hydroxy-2-phenylethyl p-tolyl sulfoxide 145 from treatment of (R)-methyl p-tolyl sulfoxide 144 with lithium diethylamide . However, a considerable stereoselectivity was observed in the reaction of this carbanion with unsymmetrical, especially aromatic, ketones The carbanion derived from (R)-144 was found to add to N-benzylideneaniline stereoselectivity, affording only one diastereomer, i.e. (Rs,SJ-( + )-iV-phenyl-2-amino-2-phenyl p-tolyl sulfoxide, which upon treatment with Raney Ni afforded the corresponding optically pure amine . The reaction of the lithio-derivative of (-t-)-(S)-p-tolyl p-tolylthiomethyl sulfoxide 146 with benzaldehyde gave a mixture of 3 out of 4 possible isomers, i.e. (IS, 2S, 3R)-, (IS, 2R, 3R)- and (IS, 2S, 3S)-147 in a ratio of 55 30 15. Methylation of the diastereomeric mixture, reduction of the sulfinyl group and further hydrolysis gave (—)-(R)-2-methoxy-2-phenylacetaldehyde 148 in 70% e.e. This addition is considered to proceed through a six-membered cyclic transition state, formed by chelation with lithium, as shown below . ... 

The present method is successful with a wide variety of ketones (see Table). Cyclic ketones (entries 1-4, 8) produce benzoannelated products in excellent overall yields. There is no need to purify the intermediate both the nucleophilic addition of methallylmagnesium chloride and the aromatic cyclization take place cleanly. Acyclic ketones (entries 5-7) also provide high yields of benzoannelated product. Aromatic ketones are particularly interesting substrates for this reaction since they provide substituted biphenyls, which are potentially useful materials for liquid crystal synthesis and whose preparation through classical methodology is often not straightforward. The conditions for the cationic cyclization step can be modified to accommodate acid-sensitive functionality. For example, cyclization of 3 to 4, the latter a precursor for 3-methyl-8,14-dehydromorphinan, was accomplished in 77% yield by treatment of 3 at... 

New chiral oxazaborolidines that have been prepared from both enantiomers of optically active inexpensive a-pinene have also given quite good results in the asymmetric borane reduction of prochiral ketones.92 Borane and aromatic ketone coordinate to this structurally rigid oxazaborolidine (+)- or (—)-94, forming a six-membered cyclic chair-like transition state (Scheme 6-41). Following the mechanism shown in Scheme 6-37, intramolecular hydride transfer occurs to yield the product with high enantioselectivity. With aliphatic ketones, poor ee is normally obtained (see Table 6-9). 

As with the aldehyde reductases, ketone reductases are specific for NADPH as reductant. Also, some isoenzymes of ketone reductase have not been purified to homogeneity and therefore not fully characterized. It is clear, however, that the ketone reductases catalyze reduction of aromatic, aliphatic, cyclic, and unsaturated ketones to the corresponding alcohols. The ketone reductases also catalyze reduction of aromatic and aliphatic aldehydes to primary alcohols. The distribution and specificity of ketone reductases has been reviewed (103). 

The propargylic alcohol 102, prepared by condensation between 100 and the lithium acetylide 101, was efficiently reduced to the hydrocarbon 103, which on treatment with potassium tert-butoxide was isomerized to the benzannulated enyne-allene 104 (Scheme 20.22) [62], At room temperature, the formation of 104 was detected. In refluxing toluene, the Schmittel cyclization occurs readily to generate the biradical 105, which then undergoes intramolecular radical-radical coupling to give 106 and, after a prototropic rearrangement, the llJ-f-benzo[fo]fluorene 107. Several other HJ-f-benzo[fo]fluorenes were likewise synthesized from cyclic aromatic ketones. 

An interesting deoxygenation of ketones takes place on treatment with low valence state titanium. Reagents prepared by treatment of titanium trichloride in tetrahydrofuran with lithium aluminum hydride [205], with potassium [206], with magnesium [207], or in dimethoxyethane with lithium [206] or zinc-copper couple [206,209] convert ketones to alkenes formed by coupling of the ketone carbon skeleton at the carbonyl carbon. Diisopropyl ketone thus gave tetraisopropylethylene (yield 37%) [206], and cyclic and aromatic ketones afforded much better yields of symmetrical or mixed coupled products [206,207,209]. The formation of the alkene may be preceded by pinacol coupling. In some cases a pinacol was actually isolated and reduced by low valence state titanium to the alkene [206] (p. 118). 

All reducing agents used for reductions of aliphatic and aromatic ketones can be used for reduction of cyclic ketones to secondary alcohob (pp. 107 and 109). In fact, reduction of cyclic ketones is sometimes easier than that of both the above mentioned categories [262]. What is of additional importance in the reductions of cyclic ketones is stereoselectivity of the reduction and stereochemistry of the products. 

This protocol complements Akiyama s method which provides P-amino carbonyl compounds as i yn-diastereomers [14], It tolerated aromatic, heteroaromatic, and aliphatic aldehydes. Cyclic ketones, acetone, as well as acetophenone derivatives could be employed. The use of aromatic ketones as Mannich donors was up to that time unprecedented in asymmetric organocatalysis. Rueping et al. independently expanded the scope of the asymmetric Brpnsted acid-catalyzed Mannich reaction of acetophenone [45]. 

Conversion of Various Aliphatic, Aromatic and Cyclic Ketones. 83... 

Later in 2007, Gong utilized If and saturated derivative 2 in a direct Mannich reaction between in situ generated N-aryl imines and cyclic ketones as well aromatic ketones (Scheme 5.3) [10], It was found that electron poor anilines as coupling partners gave the highest enantioselectivities. The authors postulate that acid promoted enolization of the ketone forms the reactive enol which adds to the protonated aldimine. 

TS-1 zeolites have been used in the presence of H2O2 to perform the BV reaction on cyclic and aromatic ketones . Cyclohexanone and acetophenone can be oxidized at 80 °C with selectivities lower that 60%, due to the formation of a-hydroxyketones and other undesired products. The observed modest results seem to be associated with the poor selectivity of the active Ti-peroxo species. In this respect, Corma and coworkers developed new Sn-based heterogeneous catalysts able to selectively activate the ketone instead of 11202 . Cyclic ketones are transformed into the corresponding lactones and unsaturated cyclic ketones like 110 are oxidized to unsaturated lactones in very high chemoselectivitjf , unusual for other oxidizing systems (equation 75). As expected, the authors failed to detect the presence of metal-peroxo derivatives in their systems . ... 

The Vaportech technology has been used in the past to treat soils contaminated with chlorinated solvents such as perchloroethylene (PERC) and trichloroethylene (TCE) benzene, toluene, ethylbenzene, xylenes (BTEX) aromatics, ketones, gasoline-range and diesel-range organics, phenols, and other cyclic and noncyclic carbon compounds including ketones, naphtha, mineral spirits, and lacquer diluter. 

R) -specific ADH from L. kefir was used for the reduction of various ketones to the corresponding secondary alcohols. Aliphatic, aromatic, and cyclic ketones as well as keto esters were accepted as substrates. The activities achieved with several substrates were compared with the activity obtained with the standard substrate of ADH, acetophenone (Fig. 2.2.4.4). As the figure shows, recombinant LK-ADH has a very broad substrate spectrum, including many types of ketones. 

An analogous non-electrochemical Ni(0)-catalysed process, exploited in a Mannich/ Reformatsky multicomponent process58, will be discussed in Section III (equation 41). In the third study, the a-bromoester Id is simply electrolysed in the presence of a carbonyl compound in DMF/THF in a 1 2 ratio using both indium and zinc rods as sacrificial anodes. While aldehydes afford the expected 3-hydroxyesters in high yield, aliphatic, aromatic and cyclic ketones, with the exception of acetone, directly afford /3-lactones,... 

Aromatization of cyclic ketones 9-12 Oxidative cleavage of alkylbenzenes... 

Because of its high crystallinity, the hnmopolymer (PVDV) is insoluble in most solvents at room temperature. However, since the regularity of repeating units in the chain is decreased by copolymerization, Saran is soluble in cyclic ethers and aromatic ketones. This copolymer (100 g) is plaslicized by die addition of a-melhyl-benzyl ether (5 g), stabilized against ultraviolet light degradation by 5-chloro-2-hydroxybenzophenone (2.0 g) and heat stabilized by phenoxypropylene oxide (2.0 g). 

In contrast, aromatic ketones are high boiling, colorless liquids that generally have a fragrant odor and are almost insoluble in water. They are useful as intermediates in chemical manufacture. Functionalized and cyclic ketones are also good solvents. Ring size and the type and location of functional groups affect odor, color, and reactivity of these ketones. 

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