Ethynyl ketones, reaction with

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)). 

Oppenauer oxidation of the enol ether (34) affords the corresponding 17 ketone (37) (the enol ether is stable to the basic oxidation conditions). This ketone affords the corresponding 17a-ethynyl compound on reaction with metal acetylides. Hydrolysis of the enol ether under mild conditions leads directly... 

Reactions with Aldehydes and Ketones Crotone-type products have been obtained in reactions of nitrones (295a, R2=OH) with p-ethynyl-, p-bromo-, and p-iodobenzaldehydes (Scheme 2.119) (542, 543). 

Buynak et al. reported the synthesis of representative 7-vinylidenecephalosporine derivatives bearing an axial allene chirality (Scheme 4.5) [9]. A chiral allene 24 was prepared stereoselectively utilizing the reaction of an organocopper reagent with propargyl triflate 23, obtained by a diastereoselective ethynylation of the ketone 22 with ethynylmagnesium bromide. Terminally unsubstituted allene 26 was synthesized via bromination of the triflate 23 followed by reduction of the bromide 25 with a zinc-copper couple. 

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

Oppenauer oxidation of the enol ether (34) affords the corresponding 17 ketone (37) (the enol ether is stable to the basic oxidation conditions). This ketone affords the corresponding 17a-ethynyl compound on reaction with metal acetylides. Hydrolysis of the enol ether under mild conditions leads directly to ethynodrel (39), an orally active progestin. This is the progestational component of the first oral contraceptive to be offered for sale. Treatment of the ethynyl enol ether with strong acid leads to yet another oral progestin employed as a contraceptive, norethindrone (40). ° In practice these and all other so-called combination contraceptives are mixtures of 1-2% mestranol... 

In contrasi to many acetylenes RCsCH, chloroacetylene can be successfully coupled with ketones in liquid ammonia via the lithium compound [80,85], The excellent yield in the reaction with acetone indicates that practically no formation of enolate occurs. Similar good results have been obtained with lithiated ethynyl thioethers, (LiCsCSR), lithiated enyne thioethers, (LiCsCCH=CHSR), lithiated 1,3-diynes (RC=CC=CLi), and lithiated aiylacetylenes (LiCsCAryl)[2], A possible explanation for the small extent of enolization of the ketone is that all these acetylides are less basic due to some stabilization of the anion. 

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 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. 

The reaction of the lithio derivative of the diethyl acetal of the polyenynal 304 with the polyenyne ketone 305 followed by acid hydrolysis gave the hydroxyaldehyde 306. The ethynyl ketone 307 obtained by the aldol condensation of 306 with pinacolone was ethynylated" to give 308. Oxidative coupling of 308 yielded the... 

The substituted acetylenic ketone (313), formed by quaternization of the free amine (174) (see p. 268), undergoes internal condensation on reaction with potassium t-butoxide, to give the 3of-ethynyl-A-nor-3, 5)3-epoxide (314). " A possible mechanism is illustrated. 

Similarly, the 2-azidoethylene-l,l-dicarbonitriles (92) were found to react with aniline to give the corresponding anilino derivatives 121 Reaction of phenyl ethynyl ketone with sodium azide in an aqueous medium, it will be recalled, gave the isoxazole 74 (R = H). When this reaction was carried out in dimethylformamide, quite different results were found in this case the sodium salt of 4-benzoyl-1,2,3-triazole was isolated in good yield . The formation of this product... 

The utility of this reagent has been demonstrated by Tamura et al. in its reaction with the readily enol-izable ketone The ethynylation of the ketone proceeds smoothly with the cerium reagent, as... 

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