Aromatic cyclic ketones

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. 

Aldehydes and ketones, both aromatic and aliphatic (including cyclic ketones), can be converted in high yields to dimeric alkenes by treatment with TiCl3 and a zinc-... 

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. 

A BINAP-Ir-aminophosphine system effectively promotes hydrogenation of cyclic aromatic ketones in a 5 1 dioxane-CH3OH mixture under 50-57 atm of hydrogen at 90°C to give... 

Ketones were found to be the major volatile components in boiled crayfish tail meats. A total of seven saturated ketones (C6 - Cll), one unsaturated ketone, one cyclic ketone, one aromatic ketone and two alkanediones were identified in the boiled crayfish tail meat. The two alkanediones, 2,3-butanedione and 2,3-pentanedione, gave an intense buttery and desirable aroma. Acetophenone imparted sweet rose floral odor. Four methyl ketones (C7 - Cll) and 2,3-pentanedione were identified in boiled crayfish hepatopancreas. Pour methyl ketones (C5 - C8) were identified in pasteurized crahmeat. These methyl ketones were usually associated with green, fruity aromas and gave more floral aromas as chain length increased. Several ketones (C4 - C8) also have been reported as volatile flavors of shrimp (13). The diketones might be important aroma components for crayfish tail meat and hepatopancreas products in providing desirable balance of the meaty and buttery notes. 

Food, flavors consist of numerous compounds, none of which alone is characteristic of specific food. Classes of compounds which emcompass food flavors are - hydrocarbons (aliphatic, ali-cyclic, aromatic) carbonyls (aldehydes, ketones) carboxylic acids, esters, imides, anhydrides alcohols, phenols, ethers alkylamines, alkylimines aliphatic sulfur compounds (thiols, mono-, di- and tri-sulfides) nitrogen heterocyclics (pyrroles, pyrazines, pyridines) sulfur heterocylics (thiophenes, thiazoles, trithiolane, thialidine) and oxygen-heterocyclics (lactone, pyrone, furan). Discussion will be limited to striking developments in heterocyclics. 

Ionic liquids (imidazolium salts) were utilized as green solvents in the Friedlander synthesis. Reactions of o-amino-substituted aromatic carbonyls with a variety of ketones (cyclic, acyclic, aromatic) result in the desired quinolines in uniformly high yield. Conditions are mild and no hazardous acids or bases are used <03JOC9371>. 

A combined system of the BINAP-Ir complex and bis(o-dimethylaminophenyl)phenylphosphine or (o-dimethyl-aminophenyl)diphenylphosphine catalyzes hydrogenation of benzylideneacetone and cyclic aromatic ketones with modest to high enantioselectivities (eq 25). 

Hydrosilylation of unsaturated organic molecules is an attractive organic reaction. Asymmetric hydrosilylation of prochiral ketones or imines provides effective routes to optically active secondary alcohols or chiral amines (Scheme 756). These asymmetric processes can be catalyzed by titanium derivatives. The ( A ebthi difluoro titanium complex has been synthesized from the corresponding chloro compound.1659 This compound results in a very active system for the highly enantioselective hydrosilylation of acyclic and cyclic imines and asymmetric hydrosilylation reactions of ketones including aromatic ketones.1661,1666,1926-1929 An analogous l,l -binaphth-2,2 -diolato complex catalyzes the enantioselective hydrosilylation of ketones.1... 

The reaction actually produces a mixture of the primary amine and the correspond ing formyl derivative, but the amine product is exclusively isolated after the crude product is treated with H Cl (Scheme 7.3). As of this writing, the method provides low yields and ee for cyclic aromatic substrates, for example, 1 indanone (6% yield, no ee reported, chiral Ru catalyst) [11b]. Regarding aliphatic ketones, for example, 2 octanone (44% yield, 24% ee, chiral Ru catalyst [lla[ or 37% yield with an achiral Rh catalyst [11b]). The same authors have recently made inroads concerning the use of aromatic ketones and molecular hydrogen [12], although the transfer hydrogenation method presented here appears to be superior as of now. 

Reactions of free ketones with imines are far more restricted than those with preformed iminium salts. Examples of ketone-imine condensations are included in several reviews - and are limited to the use of arylimines, mainly benzylideneaniline. Blatt and Gross have noted that the reproducibility of uncatalyzed additions of ketones to Schiff bases is poor but can be improved by the addition of small amounts of hydrochloric acid. The highest yields of 3-amino ketones are obtained using 10 mol % of concentrated hydrochloric acid and 95% ethanol as solvent, and by performing the reaction at room temperature. The reaction, however, is of limited applicability, as it is restricted to methyl ketones and cycloalkanones. Deamination leading to unsaturated ketones is a major side reaction. In addition to hydrochloric acid, boron trifluoride etherate has been used as a catalyst in reactions of aromatic imines with methyl ketones, cyclic ketones and an epoxy ketone. ... 

The reacfion is affecfed by several factors, including fhe nafure of the cycloacylating functional group, the Lewis or protic acid, the nature and position of subsfifuenfs on fhe aromafic ring, and fhe size of fhe ring to be formed. In general, experimenfal conditions can be set up in order to efficiently synthesize cyclic aromatic and heteroaromatic ketones. 

Ans. (a) 3-Methylcyclohexanone. (b) Common names are used for ketones where one (or both) substituent(s) attached to the carbonyl carbon is (are) cyclic (aromatic or nonaromatic) 2-chloro-phenyl ethyl ketone or o-chlorophenyl ethyl ketone, (c) 4-Methyl-2-heptanone. (d) 2-Chloro-cyclohexanecarbaldehyde. 

FIGURE 10.3 XeF2-initiated ring expansion of cyclic aromatic ketones. 

Difluoro-2,3,4,5-tetrahydro-2//-l-benzoxepine (8) and 2,2-difluoro-2,3,4,5-tetrahydro-2//-l-benzoxocin (10) have been prepared in low yield by oxidative ring expansion reaction of cyclic aromatic ketones 7 or 9 with Xep2 (Fig. 10.3). ... 

S)-Pyrrolidine trifluoromethanesulfonamide 3a is a highly active catalyst for the asymmetric conjugate addition of aldehydes and ketones to nitroalkenes. The use of catalyst 3a (20 mol%) in i-PrOH at 0 °C, afforded a,a-dialkyl aldehydes with good to high yields and high to excellent levels of diastereo- and enantioselectivity (Scheme 9.20). In addition, the reactions of various cyclic and acyclic ketones with aromatic nitro-olefins indicated the usefulness of the catalyst. " Computational results corresponded with the observed stereoselectivities of 3a-catalysed Michael reactions. 

A multicomponent one-pot reaction involving fused cyclic ketones 154, aromatic aldehydes 156 and 2-aminothiophenol 155, promoted by tetrachlo-rosilane at ambient temperature, gave a series of indeno- and naphtho-fused 1,5-benzothiazepines 157 in good-to-excellent yields (14TL6039). 

HALOGENATED HYDROCARBONS HYDROCARBONS—ALIPHATIC HYDROCARBONS—ALIPHATIC/CYCLIC HYDROCARBONS—ALIPHATIC/CYCLIC/AROMATIC HYDROCARBONS—AROMATIC HYDROCARBONS—AROMATIC/ALIPHATIC HYDROCARBONS—CYCLIC HYDROCARBONS—UNSPECIFIED KETONES... 

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