Ethynylation ketone

Reaction of an acid chloride with trimethylsilylacetylene produces an a,P-ethynyl ketone, which on treatment with substituted hydrazines yields a mixture of 1,5- and 1,3-substituted pyrazoles (34). The ratio is dependent on the reaction conditions (eq. 3). 

With an activated C—C triple bond two successive additions can occur if the intermediate alkene is reactive enough. DMAD and 3,5-dimethylpyrazole give an initiaj fumarate (255) which reacts further at the other end to form regioselectively the succinates (256). On the other hand, methyl ethynyl ketone reacts twice at the same carbon atom with pyrazole to form 1,1-pyrazolylbutanone (258) (68ZC458). The probable intermediate, a pyrazolide vinylogue (257), can be prepared from methyl chlorovinyl ketone and pyrazole, in a reaction which is similar to acetylation (Section 4.04.2.1.3(x)). 

Isotellurazoles la-e were first prepared by coupling ethynyl ketones with hydroxylamine-O-sulfonic acid and K2Te in aqueous solution of sodium acetate... 

Disubstituted isotellurazoles 1 (4-11%) and bis((3-acylvinyl)tellurides 3 (3-10%) were isolated in very low yields from the reaction mixture as the products of nucleophilic addition of telluride anion to the triple bond of the initial ethynyl ketones (83S824). This method cannot be applied to the synthesis of 3//-isotellurazoles. When a-acetylenic aldehydes were used instead of ethynyl ketones, bis((3-cyanovinyl)tellurides 4 obtained in 14-20% yields were the only products (83S824). 

Cyclisation of o-hydroxyphenyl ethynyl ketones under basic conditions is known to produce benzopyran-4-ones and benzofuranones by 6-endo-dig and 5-exo-dig processes, respectively. However, both cyclisations are reversible in aprotic media thereby generating anions, of which that derived from the pyranone is rapidly and irreversibly protonated and hence selective formation of the chromone results <96T9427>. 

When re-alkyl ethynyl ketones were tested as the substrate of LBADH, the preferred stereochemistry and optical purity of the resulting propargylic alcohol were dependent upon the size of the alkyl group (Figure 7.26) [71]. 

Figure 7.26 Enzymatic reduction of re-alkyl ethynyl ketones by LBADH...

A series of ethynyl ketones and ethynylketoesters were reduced enantioselectively to the corresponding nonracemic propargyl alcohols using a secondary alcohol dehydrogenase from... 

The Bohlmann-Rahtz synthesis of trisubstituted pyridines from /3-aminocrotonates and an ethynyl ketone has found application in the preparation of a variety of heterocycles based on the substituted pyridine motif. Bagley and coworkers have developed a microwave-assisted modification of this one-pot heteroannulation method that is best conducted in dimethyl sulfoxide at 170 °C for 20 min, providing the desired pyridines in 24—94% yield (Scheme 6.227) [406, 407]. Typically, 2 equivalents of the /3-aminocrotonates were employed. 

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 r/.v-enamino ketone 281 is formed stereoselectively by the reaction of benzylamine with the (trimethylsilyl)ethynyl ketone 280310. 

The retrosynthesis involves the following transformations i) isomerisation of the endocyclic doble bond to the exo position ii) substitution of the terminal methylene group by a more stable carbonyl group (retro-Wittig reaction) iii) nucleophilic retro-Michael addition iv) reductive allylic rearrangement v) dealkylation of tertiary alcohol vi) homolytic cleavage and functionalisation vii) dehydroiodination viii) conversion of ethynyl ketone to carboxylic acid derivative ix) homolytic cleavage and functionalisation x) 3-bromo-debutylation xi) conversion of vinyl trimethylstannane to methyl 2-oxocyclopentanecarboxylate (67). 

The treatment of o-bromophenyl ethynyl ketones with sodium hydrogen teUuride follows a similar pathway giving tellurochromone. ... 

A solution of o-bromophenyl ethynyl ketone (10 mmol) in DMF (20 mL) was slowly added to a stirred solulion of NaHTe (12 mmol), which was prepared from tellurium... 

Analogous N/C substituted allenylidenes [M =C=C=CPh(NMeR) (CO)5] (M = Cr, W R= H, Me, Et) are obtained by using C-ethynylimines HC = CC(=NMe)Phinstead of propynoic acid amides. 0/C-, 0/0-, and N/S-substituted allenylidenes are also accessible from ethynyl ketones HC = CC(=0)R, propynoic acid esters HC=CC(=0)0R and propynethioic acid amides HC=CC(=S)NR2, respectively, after sequential deprotonation and the corresponding alkylation (representative examples are shown in Figure 2.2) [4a, 9]. 

Ethynyl Ketones by Oxidation of the Corresponding Ethynyl Carbinols with Chromic Add... 

When recLBADH was tested with n-alkyl ethynyl ketones it was observed that the preferred stereochemistry of the resulting propargylic alcohol depends on the... 

In the presence of base, alcohols and phenols add l,5-diphenylpenta-l,4-diyn-3-one (72JOU1398). At 40 °C addition occurs at both triple bonds to give a mixture of the 1,5-dialkoxy compound (411), the triketone and the pyran-4-one. On treatment with acid the former compounds are converted into the pyranone. However, at 15 °C only one triple bond is attacked giving the alkoxyvinyl ethynyl ketone (412), but this also forms the pyranone with acid (Scheme 136). 

As with Michael additions to activated alkenes, the initial adducts with activated alkynes can be trapped by various processes. An aldol reaction can occur if a carbonyl is properly situated in the starting material (Scheme 71).123 However, the use of methyl ethynyl ketone (509) and its homologs in the Robinson annulation process to give cyclohexadienones (510 equation 110) usually proceeds in poor... 

The mechanism of the alkaline decomposition of methyl ethynyl ketone—to acetate and ethyne—has been probed using AMI calculations.125... 

Reductive cyclization of y-ethynyl ketones to allylic alcohols. This reaction was first reported by Stork et al., who used an alkali metal and liquid ammonia.1 The main by-products, at least in cyclization to A-norsteroids, result from overreduction. This side reaction can be prevented by use of sodium naphthalenide in THF or DME.2... 

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

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. 

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>. 

Bromidge SM, Entwistle DA, Goldstein J, Orlek BS (1993) A convenient synthesis of masked P-ketoaldehydes by the controlled addition of nucleophiles to (trimethylsilyl)ethynyl ketones. Synth Commun 23 487-494... 

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... 

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