Potassium alkyne derivatives

In addition to alcohols, some other nucleophiles such as amines and carbon nucleophiles can be used to trap the acylpalladium intermediates. The o-viny-lidene-/j-lactam 30 is prepared by the carbonylation of the 4-benzylamino-2-alkynyl methyl carbonate derivative 29[16]. The reaction proceeds using TMPP, a cyclic phosphite, as a ligand. When the amino group is protected as the p-toluenesulfonamide, the reaction proceeds in the presence of potassium carbonate, and the f>-alkynyl-/J-lactam 31 is obtained by the isomerization of the allenyl (vinylidene) group to the less strained alkyne. 

The alkynylation of estrone methyl ether with the lithium, sodium and potassium derivatives of propargyl alcohol, 3-butyn-l-ol, and propargyl aldehyde diethyl acetal in pyridine and dioxane has been studied by Miller. Every combination of alkali metal and alkyne tried, but one, gives the 17a-alkylated products (65a), (65c) and (65d). The exception is alkynylation with the potassium derivative of propargyl aldehyde diethyl acetal in pyridine at room temperature, which produces a mixture of epimeric 17-(3, 3 -diethoxy-T-propynyl) derivatives. The rate of alkynylation of estrone methyl ether depends on the structure of the alkyne and proceeds in the order propar-gylaldehyde diethyl acetal > 3-butyn-l-ol > propargyl alcohol. The reactivity of the alkali metal salts is in the order potassium > sodium > lithium. 

As with the reaction of pyrroles, diazoles and triazoles react with propargyl bromide to yield TV-substituted products and, depending upon the base strength, either TV-prop-2-ynylazoles or allenic derivatives are formed [30]. Generally, with potassium carbonate under soliddiquid two-phase conditions at room temperature in the absence of a solvent, the prop-2-ynyl compounds are formed as sole products, whereas with solid potassium hydroxide at elevated temperatures the allenes are obtained as the major products. Benztriazole produces a mixture of the N1- and N2-prop-2-ynyl, and N2-allenic derivatives, whereas with potassium hydroxide only the N -allenic derivative is obtained. The alkynes readily isomerize to the allenes in the presence of base and the quaternary ammonium salt, or upon treatment with methanolic sodium hydroxide. A series of l-(alk-2-ynyl)imidazoles have been prepared, as intermediates in the synthesis of imidazopyridines [31 ] and the reaction of 3-hydroxymethylpyrazoles with propargyl bromide leads to pyrazolooxazines [32]. 

N-Substituted amides derived from 2-chloro- or4-chloronicotinic acid react with CH-acidic nitriles in the presence of base to yield amino derivatives of [l,6]naphthytid-5(6//)-ones and [2,7]naphthyrid-l(2//)-ones <1997JHC397>. 3-(l-Alkylamino)pyridines react with electron-deficient alkynes (acetylene dicatboxylates) in the presence of acid to give l,2-dihydro[2,7]naphthyridine-3,4-dicarboxylates in up to 72% yield compounds unsubstituted at C-1 were readily oxidized with potassium permanganate to naphthyridine-l-ones <2005TL3953>. 

A very efficient, stereospecific synthesis of DL-ribose was based26 on the use of l,l-diethoxy-5-(tetrahydropyran-2-yloxy)-2-pentyn-3-ol as the substrate. Catalytic hydrogenation of this alkyne to the cts-alkene was accompanied by cyclization, to give 2-ethoxy-2,5-dihydro-5-(tetra-hydropyran-2-yloxy)furan (35). cis-Hydroxylation of the double bond in 35 was effected with potassium permanganate, yielding the ethyl DL-ribofuranoside derivative 36, which was hydrolyzed to DL-ribose. 

With those RX derivatives that undergo nucleophilic displacement readily, this is a general method of forming a C—C bond, thereby leading to substituted alkynes. The alkynide salts generally used are those of lithium, sodium, potassium, or magnesium. 

In this chapter we will restrict our discussion of organometallic compounds to the alkyl and aryl compounds of magnesium and lithium, and the sodium and potassium salts of 1-alkynes. These substances normally are derived directly or indirectly from organohalogen compounds and are used very widely in organic synthesis. Organometallic compounds of transition metals and of boron are discussed in Chapters 11 and 31. 

Disubstituted bicyclo 2.2.1 heptanes.2i Bicyclo[2.2.1]heptene is converted into 2,3-disubstituted derivatives when treated with an aryl or vinyl bromide and an alkyne in the presence of potassium acetate (1 equiv.) and a catalytic amount of Pd[P(C6H5)3LP Example ... 

A preparation of 2,2-disubstituted 1,3-benzodithiole derivatives (278) involves the reaction of benzene-1,2-dithiols (273) with alkynic ketones in the presence of piperidine or potassium carbonate (80S115,81KGS329). 

Additionally, acetylene itself is a useful two-carbon building block but is not very convenient to handle as it is an explosive gas. Trimethylsilyl acetylene is a distillable liquid that is a convenient substitute for acetylene in reactions involving the lithium derivative as it has only one acidic proton. The synthesis of this alkynyl ketone is an example. Deprotonation with butyl lithium provides the alkynyl lithium that reacted with the alkyl chloride in the presence of iodide as nucleophilic catalyst (see Chapter 17). Removal of the trimethylsilyl group with potassium carbonate in methanol allowed further reaction on the other end of the alkyne. 

Pd species. This intermediate undergoes carbonylation, methoxy substitution, and reductive elimination to furnish the Z-configured derivative 193. The resulting Pd(0)-species is reoxidized by oxygen in the presence of iodide ions. On the other hand, the presence of potassium iodide can also equilibrate the ( 2-alkynyl carbamate-Pd-iodide complex to the r/2-alkynyl carbamate-Pd-diiodide complex, which, in turn, causes an anti-attack of the carbamate at the Pdl2-complexed alkyne. Therefore, an antz-vinyl-Pd species results, which ultimately and accordingly leads to the -configured derivative 194. Without carbon monoxide the vinyl-Pd-species suffer a hydro-demetallation. 

For a long time" , it has been known that there is rearrangement of 1-alkynes to 2-alkynes under basic conditions (for instance by alcoholic potassium hydroxide or powdered potassium hydroxide) at 175 C. It has been shown that in fact an equilibrium mixture is obtained . It contains isomeric compounds, mainly the starting 1-alkyne and isomeric 1,2-alkadiene and 2-aIkyne, but the latter, more stable from thermodynamic considerations, is predominant. Therefore the method could be used to prepare 2-alkynes from corresponding 1-alkynes. The reverse reaction is possible disubstituted acetylenes can be converted to sodium derivatives of 1-alkynes by sodium or sodamide . 1-Alkynes are recovered by hydrolysis. We have tried to apply both reactions to prepare acetylenes deuterated in defined positions with high isotopic purity. 

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