Aryl ethynyl ketones

Scheme 29 Proposed mechanism for 1,3,5-regioselective polycydotrimerization of aryl ethynyl ketone [102,103]...

Activated phenols react readily with aryl ethynyl ketones in the presence of HIT), to give flavylium salts, 3-deoxyanthocyanidins. The method has been extended to aryl di(ynones) to produce dicationic 2,2 -(phenylene)bis(benzopyrylium) salts (Scheme 21) <07EJO2438, 07SL1067>. 

Tripathi VK, Venkataramani PS, Mehta G (1979) Addition of nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to aryl ethynyl ketones. J Chem Soc Perkin Trans 1 36-41... 

A variety of aryl ethynyl ketones undergo trimerization in the presence of a trace amount of diethylamine (Table 11-4) [53-55]. Moreover, not only homotrimerization but also cross-trimerization can be performed (Table 11-5) [55]. The cross-trimerized products always contain a mixture of four kinds of trimers when starting with two kinds of ethynyl ketones, but these products can be separated by GPC. 

Aristov, S.A. Vasil ev, A.V. Rudenko, A.R Oxidation of aryl ethynyl ketones in the system CFaCOjH-CHjClz-PbOj. Zhurn. Org. Khim. 2006, 42, 74 80. 

Hexaketones, precursors of 8, 9, and 10, were synthesized from m-bromoben-zaldehyde, calix[6]arene, and tribromobenzene, respectively. In the synthetic sequence for dendritic polydiazo compounds, 11, 12, and 13, the key reaction was a cyclo trimerization reaction of aryl ethynyl ketone to form 1,3,5-triaroyl-... 

Reduction to Halocarbons. The best conditions for the reductive chlorination of ketones use the reagent combination Me2ClSiH/In(OH)3 (Eq. 241).331 Examples include conversions of aryl ketones to benzyl chlorides, ethynyl ketones to propargyl chlorides, and alkyl ketones to alkyl chlorides (Eq. 242).331 Addition of lithium iodide to the reaction mixture yields the corresponding iodide product. The combination of TMDO/I2 reductively iodinates aryl ketones and aldehydes in good yields (Eq. 243).357... 

The aryl vinyl tellurium compounds formed in these reactions (p. 401) are obtained exclusively, or at least predominantly, as the (Z)-isomers. With ethynyl ketones, aldehydes, acids, and esters, the nucleophile attacks the ethync carbon in the -position to the carbonyl group10, ". Benzenetellurolate and bis[phenylethynyl] ketone produced only bis[2-phenyl-2-phenyltelluroethynyl] ketone and no monoadduct11. 

T vo kinds of ethynyl aryl ketones were chosen as starting units. One was ethynyl ketone 50 and the other was m-propynoylphenyl trimethylsilylethynyl ketone 51. Cross-trimerization of these units afforded a mixture of four kinds of trimers trimer 53 from 3 mol of 50,2 1-trimer 52,1 2-trimer 54, and trimer 55 from 3 mol of 51. These trimers could be separated by GPC. The trimer 52 was subjected to the second trimerization reaction after deprotection to afford dodecaketone 49 [55 b]. 

For instance, photolysis of aryl esters of phenylpropiolic acid (21) gives rise to o-hydroxyaryl phenyl-ethynyl ketones (22). The latter compounds can undergo cyclization in two different ways, depending upon the reaction conditions When potassium carbonate in acetone is used, flavones (23) are formed by a 6-endo-dig process by contrast, the use of sodium ethoxide in ethanol favors the 5-exo-dig process,to give aurones (24) as the major products (Scheme 6). The side-chain functionality can be masked, as in the case of the protected ketoesters (25), whose irradiation and subsequent deprotection provide an alternative entry to the flavone system (Scheme 6). ... 

The ability of the ethynyl-l,5-azastibocines 5, to be used as alkynylation agents, has recently been demonstrated by Kakusawa et al. <2003TL8589>. The reaction of 5 with organic halides, such as acyl halides and aryl halides, in the presence of PdCl2(PPh3)2, as a catalyst, led to the formation of cross-coupling products, alkynyl ketones 109 and diaryl acetylenes 110, in good yields (Equations 9 and 10). 

Venkataramani PS, Saxena NK, Tripathi VK, Mehta G (1975) Nucleophilic addition to ethynyl aryl ketones - stereospeciflc route to disubstituted enol ethers. Indian J Chem 13 852-854... 

Kharasch and Tawney (1941) reported that copper salts catalyze 1,4-addi-tion of Grignard reagents to a,jS-unsaturated ketones. Gilman et al. (1952) first discovered that phenylcopper reacts with benzalacetophenone in a 1,4-addition. Subsequently House and associates (1966) have revealed the scope of the conjugate addition of cuprate complexes. Now alkyl, vinyl, and aryl groups can be introduced specifically at the p position of a,jS-unsaturated carbonyl compounds. Transfer of an allyl group from lithium diallylcuprate to 2-cyclohexenone is also known (House and Fischer, 1969). However, ethynyl, cyano, and hetero groups attached to the copper atom are difficult to transfer to electron-poor olefins. 

Among the applications of allyl silanes reported this year their reaction with phenylselenyl chloride and subsequent oxidation of the resulting allyl selenides to allylic alcoholshas been used in the sequence outlined in Scheme IS. 3-Bromoallyltrimethylsilane therefore behaves as a hydroxypropenyl synthon. Nitroalkenes react with allylsilanes to give, after hydrolysis, y,S-unsaturated ketones, and a synthesis of substituted cyclopentenones based on this procedure has been described.Allyl trimethylsilyl ethers undergo a palladium-promoted coupling with aryl iodides to give /3-aryl-a,/3-unsaturated ketones, and palladium also catalyses the reaction of various aryl bromides with trimethylsilyl acetylene to produce ethynylated aromatics. 

Several helical polycyclic aromatic hydrocarbons bearing aryl substituents at the most sterically hindered position were synthesized in an efficient three-step cascade reaction. The initial benzannulated enediynes were synthesized by the reaction of appropriate lithium acetylenides with an aryl-rert-butyl ketone. This was followed by reduction of the resultant acetylenic propargyl type alcohol with triethylsilicon hydride. This method turned out to be particularly successful for the synthesis of helical molecules. The reaction of ketones 3.588 and 3.590 with the lithium derivative of l-ethynyl-2-(2-penylethynyl)benzene 3.545 or related binaphthyl derivative followed by reduction and three-step sequence of cascade reactions led to polycyclic aromatic compounds 3.589 and 3.591, respectively, in a good yield (Scheme 3.48) [294, 295]. 

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