1-bromo-1-lithioethene: a practical reagent for the efficient preparation of 2-bromo-1-alken-3-ols

A reliable preparative-scale synthesis of 1-bromo-1-lithioethene is reported. This reagent undergoes clean 1,2-addition with a range of aldehydes and ketones at -105 degrees C to afford the corresponding 2-bromo-1-alken-3-ols in moderate to excellent yield. Efficient diastereoselective addition to alpha-siloxy and alpha-methylcyclohexanones, as well as protected 3-keto furanose sugars, is achieved in the presence of 10 mol % CeBr(3). The resulting bromoallylic alcohol adducts have considerable potential as synthetic building blocks. [reaction: see text]     

An efficient diastereoselective route to differentially protected anti-4-amino-1-alken-3-ols

Zinc-promoted hydroxyallylation of alpha-amidoalkyl arylsulfones 4 using 3-bromo-propenyl methyl carbonate 5 proceeds smoothly in DMF at room temperature to afford high yields of differentially protected anti-1,2-amino alcohols 6.     

Practical ways from aldehydes to 2-chloro-1,1,1-trifluoro-2-alkenes and 2-chloro-1,1-difluoro-1-alken-3-ols

A reagent system CF₃CCl₃/Zn(>2 mol)/Ac₂O transformed aldehydes to 2-chloro-1,1,1-trifluoro-2-alkenes exclusively, whereas CF₃CCl₃/Zn(>2 mol)/AlCl₃(cat.) converted aldehydes into 2-chloro-1,1-difluoro-1-alken-3-ols.     

Alcoholysis of 3-alkoxy-2-cyclohexene-1-thiones

Russian Journal of Organic Chemistry -     

Synthese von 1-Aryl-2-azido-2-alken-1-onen

Zusammenfassung Durch Kondensation von -Azidoacetophenonen mit aliphatischen Aldehyden wurden 1-Aryl-2-azido-2-alken-1-one erhalten. Die Thermolyse dieser Verbindungen gab Azirine, die sich mit Cyclopentadien in 2-Azatricyclo[3.2.1.0^2.4]-6-octene überführen lassen.

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Synthesis of 1-aryl-2-azido-2-alken-1-ones (ene-azides, V)

1-Aryl-2-azido-2-alken-1-ones were obtained by condensing -azidoacetophenones with aliphatic aldehydes. Thermolysis of these compounds gave azirines, which can be converted to 2-azatricyclo[3.2.1.0^2.4]-6-octenes by reaction with cyclopentadiene.

     

Synthesis of 1-alkyl-2-methylazetidin-3-ones and 1-alkyl-2-methylazetidin-3-ols

Several 1-alkyl-2-methylazetidin-3-ones were prepared in good yield by the hydride-induced cyclization of the corresponding β-bromo-α,α-dimethoxyketimines, the resulting 3,3-dimethoxyazetidines being hydrolyzed by acid. Imination of these 1,2-disubstituted azetidin-3-ones, followed by alkylation under kinetic control conditions resulted in regioisomeric mixtures of 2,4- and 2,2-dialkylated compounds. Analytical samples of the major 2,4-disubstituted derivatives were obtained after extensive chromatographic separation. The cis stereochemistry of the major 2,4-dialkylated isomer was demonstrated on the basis of NMR data.     

Photochemical and thermal addition of alcohols to 2-cyanofuran : 1-alkoxy-2-cyanocyclopropane-3-carboxaldehydes; 2-alkoxy-3-cyano-2, 3-dihydrofuran; 1-alkoxy-1-(2-furan)-methylenimine; photochemical ring contraction; cis-trans-isomerization of dihydrofurans

The photolysis of 2-cyanofuran in alcohols yields 1-alkoxy-2-cyanocyclopropane-3-carboxaldehydes as the major products, which rearrange thermally to trans-2-alkoxy-3-cyano-2,3-dihydrofurans and small amounts of cis-isomers. Thermal mutual rearrangements between trans- and cis-2- alkoxy-3-cyano-2, 3-dihydrofurans were studied. Liquid phase thermal addition of alcohols in a temperature range between 100° and 200° yields 1-alkoxy-1-(2-furan)-methylenimines, which rearrange photochemically to 2-furyl-methylamino-ketone in case of the methoxy derivative. 3-Cyano-furan does not yield photoaddition or thermal addition products. The different behaviors of 2- and 3-substituted furans are discussed.     

Asymmetric methallylboration of prochiral aldehydes with methallyldiisopinocampheylborane·synthesis of 2-methyl-1-alken-4-ols in ≥ 90% enantiomeric purities

Methallyldiisopinocampheylborane, on condensation with aldehydes, provides 2-methyl-1-alken-4-ols in ≥ 90% enantiomeric purities.     

Synthesis of 2-alkoxy-3-chlorotetrahydrofurans

A simple one-stage method for the synthesis of 2-alkoxy-3-chlorotetrahydrofurans has been developed which is based on the chlorination of tetrahydrofuran with sulfuryl chloride at 55–65 C with the subsequent addition of an alcohol (without the isolation of the dichlorinated tetrahydrofurans). Eight compounds of the type mentioned have been synthesized by this method, six of them being previously unknown.     

Synthesis of 3-alkoxy-2-nitroxypropyl-N-alkylnitramines

It was shown that 3-alkoxy-2-nitroxypropyl-N-alkylnitramines can be prepared by nitration of the corresponding 3-alkoxy-2-hydroxypropyl-N-alkylsulfamates. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1987–1989, November, 1997.     

Alkylation of 1-alkoxy-3-methyl-1-triazene 2-oxide sodium salts

1-Alkoxy-3-methyl-1-triazene 2-oxide sodium salts react with chloromethyl methyl sulfide to give a mixture of 1-alkoxy-3-methyl-3-(methylthiomethyl)-1-triazene 2-oxides and 3-alkoxy-1-methyl-3-(methylthiomethyl)-1-triazene 2-oxides. The reaction of these triazene oxide sodium salts with 3,3-dialkyl-1-chloromethoxy-1-triazene 2-oxides produces a complex mixture of product bearing the oxytriazene moieties of the starting alkoxy-1-triazene 2-oxides bonded with the methylene group as a key structural fragment.     

Synthesis of 2-alkoxy-3-chlorotetrahydrofurans

A simple one-stage method for the synthesis of 2-alkoxy-3-chlorotetrahydrofurans has been developed which is based on the chlorination of tetrahydrofuran with sulfuryl chloride at 55–65? C with the subsequent addition of an alcohol (without the isolation of the dichlorinated tetrahydrofurans). Eight compounds of the type mentioned have been synthesized by this method, six of them being previously unknown.     

Cyclocondensation between fatty acid hydrazides and 1,1,1-trifluoro-4-alkoxy-3-alken-2-ones: Introducing a trifluoromethylated head onto fatty acid moieties

This paper reports the regioselective synthesis of new trifluoromethylated lipid derivatives, namely, 1-(5-hydroxy-5-trifluoromethyl-3-alkyl-4,5-dihydro-1H-pyrazol-1-yl)alkan-1-ones, through cyclocondensation reactions between a series of fatty hydrazides (palmitoyl, stearoyl, and oleoyl hydrazides) obtained from fatty acids from renewable resources (1,1,1-trifluoro-4-alkoxy-3-alken-2-ones [F₃CC(O)CH?C(R¹)OR, where R¹?=?H and R?Et; R¹?=?–(CH₂)₆CH₃, –(CH₂)₆CH₃, –(CH₂)₈CH₃, –(CH₂)₉CH₃, –(CH₂)₁₀CH₃, –(CH₂)₁₂CH₃, –(CH₂)₂Ph], and R?Me). Experimental observations showed that the lipophilic characteristic of 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles (5–7) prevent the acid catalyzed dehydration to aromatization of 1H-pyrazole ring, although in some cyclocondensations a proportion of the aromatic derivative 1-(5-trifluoromethyl-3-alkyl-1H-pyrazol-1-yl)alkan-1-one was obtained. All products were characterized using multinuclear (¹H, ¹³C, ¹⁹F) NMR spectroscopy.     

Synthesis of 1-alkoxy-3-(2-hydroxyethyl)-1-triazene 2-oxides

Synthetic procedure to access the first representatives of a new series of 3-monosubstitued functional derivatives of 1-alkoxy-1-triazene 2-oxides, i.e., 1-alkoxy-3-(2-hydroxyethyl)- and 1-alkoxy-3-(2-acetoxyethyl)-1-triazene 2-oxides, were elaborated. 1-Alkoxy-3,3-bis(2-hydroxyethyl)-1-triazene 2-oxides were used to derive 3-(2-acetoxyethyl)-, 3-(2-bromoethyl)- and 3-(2-cyanoethyl)substituted 1-alkoxy-3-(2-acetoxyethyl)-1-triazene 2-oxides.