I. M. Lyapkalo

Robust and efficient, yet uncatalyzed, synthesis of trialkylsilyl-protected cyanohydrins from ketones.

High-yielding cyanosilylation of ketones with NaCN and various chlorotrialkylsilanes in DMSO proceeds smoothly without catalysis to give silyl-protected ketone cyanohydrins. The unique role of DMSO consists in rendering naked cyanide anions that reversibly add to the C double bond O bond at the rate-determining step followed by fast trapping of the transient tertiary sodium cyanoalcoholates with chlorotrialkylsilanes or in situ generated cyanotrialkylsilanes. Preparatively, the reaction matches the best known catalytic cyanosilylation systems applying expensive Me(3)SiCN and demonstrates unprecedented efficiency in the synthesis of sterically congested trialkylsilyl-protected cyanohydrins.

β,β′-functionalized N,N-divinyl-N-trimethylsilyloxyamines via silylation of β-substituted aliphatic nitro compounds. The investigation of the mechanism of the process using selective trapping reagents

Abstract Hitherto unknown N,N-divinyl-N-trimethylsilyloxyamines of the general formula [XC(R)=ch]2NOSiMe3 (X = CO2Me. CN. 5-methyloxycarbonylisoxazolin-3-yl; R = H, Me, CH(Me)CO2Me) were obtained with moderate to good yields by silylation of nitro compounds XCH(R)CH2NO2 with N,O-bis(trimethylsilyl)acetamide. The mechanism of this reaction was studied by the example of silylation of methyl-3-nitropropionate using selective trapping reagents. Trimethylsilyl ester of the starting aci-nitro compound and methyl 2-nitroso acrylate were intercepted as consecutive intermediates. Thus, the silylation of β-functionalized nitro compounds could be presented as a convenient route to practically unknown β-substituted nitroso-alkenes XC(R)=CHNO which behave as active 1,3-heterodienes towards ethyl vinyl ether used as trapping reagent.

Me3SiBr-mediated intramolecular cyclization of γ-functionalized trimethylsilyl nitronates

Abstract The silylation of nitro compounds of general formula X 1 X 2 CHCH(Ar)CH 2 NO 2 with Me 3 SiBr Et 3 N at −30°C leads to hitherto unknown 2-( N , N -bis(trimethylsilyloxy)amino-2,3-dihydrofurans (X 1 =PhCO, X 2 =H) or to N , N -bis(trimethylsilyloxy)aminocyclopropanes (X 1 =X 2 =COOMe). N , N -Bis(trimethylsilyloxy)immonium cations appear to be the key intermediates in this process.

The exhaustive silylation of 5-nitro-pentan-2-one: novel processes and opportunities

Abstract Treatment of 5-nitro-pentan-2-one (1) with Me3SiOTf/Et3N leads to initial silylation of the C(O)Me-group to give regioisomeric silyl enol ethers 2a and 2b followed by double silylation of the NO2-group furnishing a mixture of N,N-bis(silyloxy)enamine 4a and enoxime TMS ether 6. Employment of a large excess of Me3SiOTf/Et3N triggers a cascade of eliminations and silylations to give a mixture of (E)-4-trimethylsilyloxy-2-trimethylsilyl-pent-2,4-dienenitrile (8) and 3-oxo-1-(1,1,1-trimethylsilyl)-1-cyclobutanecarbonitrile (9). The use of Me3SiCl/DBU changes the selectivity of silylation of 1 to give silyl nitronate 2c.

Silylation of γ, γ-bis(alkoxycarbonyl)-substituted aliphatic nitro compounds: Synthesis of N, N-bis(trimethylsilyloxy)aminocyclopropanes

Silylation of γ,γ-bis(alkyloxycarbonyl)-β-aryl- and γ,γ-bis(alkyloxycarbonyl)-β-alkyl-substituted aliphatic nitro compounds proceeds stereoselectively to give the corresponding N,N-bis(trimethylsilyloxy)aminocyclopropanes in high yields. These compounds can be used as synthetic equivalents of nitrosocyclopropanes.

General Synthesis of γ-Functionalized β-Aryl-Substituted Primary Nitro Compound

A simple and general procedure was developed for synthesis of γ-functionalized β-aryl-substituted; primary nitro compounds from aromatic aldehydes, carbonyl compounds with an activated methylene group, and nitromethane.

A NOVEL GENERAL METHOD FOR THE SYNTHESIS OF NITRONES BY REACTION OF NITROSO COMPOUNDS WITH ANIONS OF ALIPHATIC NITRO COMPOUNDS

Anions of aliphatic nitro compounds R1R2C=NO2− react with nitroso compounds RNO to give nitrones R1R2C=N(O)R. Salts of nitro compounds with metals and Et3N, as well as trimethylsilyl nitronates in the presence of F−, can serve as the sources of the anions. The structure of the nitrones was established by NMR spectroscopy. 1,3-Dipolar cycloaddition of a series of the nitrones obtained to olefins was investigated.

Trimethylsilyl derivatives of aliphatic nitro compounds in α,β-C,C-cross-coupling

A new α,β-C,C-cross-coupling reaction of derivatives of aliphatic nitro compounds, silyl nitronates andN,N-bis(silyloxy)enamines, leading to β-nitro oximes was found. The scope and limitations of this reaction were studied, and a mechanism was proposed.

New reactions of aci-1-nitropropane trimethylsilyl ester with 4-nitronitrosobenzene in the presence of trimethylsilylating reagents

We found new unusual reactions of trimethylsilyl ester of aci-l-nitropropane (1) with 4-nitronitrosobenzene (2) in the presence of silylating reagents (Scheme 1). The reaction of compound 1 (1.2 equiv.) with compound 2 (1 equiv.) in the presence of MeC(OSiMe3)=NSiMe 3 (BSA) (2.5 equiv.) affords N(4-nitrophenyl)-N-(1 -acetylaminopropyl)N-trimethylsilyloxyamine (3), which is converted into N-(4nitrophenyl)-N-(1-acetylaminopropyl)hydroxylamine (4) on treatment with a catalytic amount of KF in MeOH. At the same time, the reaction of compound 1 (1.3 equiv.) with compound 2 (1 equiv.) in the presence of Me3SiCI/Et3N (2.5 equiv.) yields 1-(4-nitrophenylimino)-2-(trimethylsilyloxyimino)propane 1-N-oxide (5) (see Scheme 1). One may assume that l-(4-nitrophenylimino)propane N-oxide (A) is the key intermediate of both reactions. At present, the mechanism of these transformations and the possibility of conducting them using other substances are being studied.

ACYLATION OF ALIPHATIC DIAMINES WITH METHYL NITROACETATE

N,N′-Bis(nitroacetyl)diamines were synthesized for the first time by the reaction of methyl nitroacetate with aliphatic diamines in H2O or EtOH in the presence of pyridine or imidazole. In the case of 1,2-ethylenediamine, theN-mononitroacetyl derivative was isolated as an intermediate product.