M. M. Demina

The reaction of methyl diazoacetate with 4,4-dimethyl-2-pentyn-1-al and related compounds

Abstract Methyl 2-diazo-3-hydroxy-6,6-dimethyl-4-heptynoate was prepared by treating 4,4-dimethyl-2-pentyn-1-al with methyl diazoacetate at room temperature in the absence of catalysts. In the case of related aldehydes, RCCCHO (R = n-Bu, Me3Si, Et3Si, Et3Ge), this unusual reaction is partially or completely suppressed by a competing 1,3-cycloaddition process. The latter leads to a mixture of isomeric 3- and 4-formylpyrazole, one of which cyalodimerizes to form tricyclic hemiaminal.

1,3-dipolar cycloaddition of trimethylsilyl azide to propynals and dimerization of 1H-1,2,3-triazole-5-carbaldehydes to tricyclic bis-hemiaminals

Reactions of trimethylsilyl azide with 3-trimethylsilyl-2-propynal and 2-propynal were studied. X-Ray analysis of the molecular structure of 4-trimethylsilyl-1H-1,2,3-triazole-5-carbaldehyde showed that the carbonyl group appears in the s-cis conformation with respect to the double C=C bond in the heteroring. The effect of the temperature and polarity of the medium on the ability of 1H-1,2,3-triazole-5-carbaldehyde to undergo dimerization to tricyclic bis-hemiaminals was examined by IR and 1H NMR spectroscopy.

Universal method for trimethylsilylation of acetylenic alcohols and glycols

Abstract A highly convenient universal method for trimethylsilylation of acetylenic alcohols and glycols via treatment by hexamethyldisilazane in the presence of benzoic acid sulphimide as a catalyst has been developed. The rate of trimethylsilylation of acetylenic alcohols is reduced from primary to secondary and to tertiary alcohols accordingly, as well as with the decreasing of hydroxyl nucleophylicity. The toxicity of trimethylsilyl acetylenic ethers, except 2-trimethylsiloxy-3-butyne, is much lower than that of original compounds.

Highly efficient synthesis of 4-trialkylsilyl(germyl)-1H-1,2,3-triazole-5-carbaldehydes

A combination of such important properties of the triazole ring as chemical stability, large dipole moment, heteroaromatic character, and the ability to form hydrogen bonds via donor–acceptor interactions were efficiently utilized in organic synthesis in the design of biologically active molecules and new materials [1]. Although 1,2,3-triazole ring is lacking in natural compounds, synthetic and biochemical studies on 1,2,3-triazole derivatives have gained a new impetus in recent years due to their use as bioisosters of amide group in the design of new effective and safe drugs [2].

Synthesis of 4-Trialkylsilyl(Germyl)-1H-1,2,3-Triazolecarbaldehyde Oximes*

Methods for the synthesis of 4-trialkylsilyl(germyl)-1H-1,2,3-triazole-5-carbaldehyde oximes have been developed. Microwave activation was shown to be highly efficient in the oximation of 1H-1,2,3-triazole-5-carbaldehydes containing silicon or germanium and also in achieving a multicomponent synthesis of 4-trialkylsilyl-1H-1,2,3-triazole-5-carbaldehyde oxime via the reaction of 3-trimethyl-silylprop-2-yn-1-al with trimethylsilyl azide and hydroxylamine.

Decisive role of water in efficient noncatalyzed synthesis of polyfunctional 1H-1,2,3-triazoles proceeding from γ-hydroxypropynals

A highly efficient method was developed for the synthesis of new polyfunctional 1H-1,2,3-triazoles by the reaction of γ-hydroxypropynals with trimethylsilyl azide in water at room temperature without catalyst. The addition of trimethylsilyl azide to γ-hydroxypropynals occurs regioselectively: Previously unknown hydroxyalkyl-1H-1,2,3-triazolecarbaldehydes have been isolated in 69-96% yields with the prevalence of 1,5-isomers and the content of minor 1,4-isomers equal 9-21%. In the reaction of γ-hydroxypropynals with sodium azide in DMSO the formation of 4-hydroxyalkyl-1H-1,2,3-triazole-5-carbaldehydes is accompanied by the dimerization of initial aldehydes into the corresponding 1,3-dioxolanes.

The aldol-type condensation of methyl diazoacetate with 3-organyl-silyl and -germyl propynals and their carbon analogues

Abstract The optimal conditions for the uncatalyzed, selective addition of methyl diazoacetate (I) to the carbonyl group of the substituted propyn-1-als RCCCHO (II) (R = alkyl, Alk 3 Si, Et 3 Ge) to give the corresponding methyl esters of 2-diazo-3-hydroxy-4-pentyn carboxylic acid RCCCH(OH)C(N 2 )COOMe (III) have been found. Shielding of the triple bond in II by the bulky R group or complexation with dicobalt octacarbonyl, the presence of strong electron acceptor (4-NO 2 C 6 H 4 ) in the 3-position of II, and the low polarity of the solvent result in the selective aldol type condensation. The reaction of γ-hydroxy-propynals R 1 R 2 C(OH)CCHO with methyl diazoacetate also proceeds by the aldol-type addition and involves two molecules of the propynal with the formation of diacetylenic diazotetraoles (VIII). The β-addition of methyl diazoacetate to the triple bond in trialkylsilyl or -germyl propynals leads to the isomeric formyl pyrazoles, IV and V. The presence of the Si- or Ge-containing substituents in the 4-position of IV promotes their dimerization into the tricyclic hemiaminals, VI.

Interaction of heteroatom-containing propynals with S-, N-binucleophiles

Reactions of α-silicon-and α-germanium-containing acetylenic aldehydes with 2-aminoethanethiol, ethylenediamine, and 2-amino-1,2,4-triazole proceed chemoselectively at the aldehyde group. The ratio of tautomers, azomethine and 1,3-thiazolidine, on interaction with 2-aminoethanethiol depends significantly on the nature of the heteroatom at the triple bond of the aldehyde, the presence of a catalyst, and the use of microwave activation.

An unusual rearrangement of 1-trimethylsiloxy-3-bromomagnesium-2-propyne

3-Trimethylsilyl-2-propyn-1-ol (4) was synthesized via the rearrangement of 1-trimethylsiloxy-3-bromomagnesium-2-propyne and followed by hydrolysis of the latter. The yield of compound 4 depends largely on the solvent used.

Reaction of 3-trimethylsilylprop-2-ynal with α-hydroxyamino oximes

Abstract3-Trimethylsilylprop-2-ynal reacted with aliphatic α-hydroxyamino oximes in a chemoselective fashion at the aldehyde group to give hitherto unknown open-chain 3-trimethylsilylprop-2-yn-1-ylideneamine oxides. The possibility for intramolecular hydrogen bonding with participation of OH, C≡C, and N→O groups in the products was studied by IR spectroscopy.