Aromatisierung von cytclohexenon-derivaten über selenorganische zwischenstufen

Reaction of the hydroaromatic compounds ($\text{1a}$) and ($\text{3a}$) with lithium-diisopropylamide followed by phenylselenenyl chloride gives the selenides ($\text{1b}$) and ($\text{1c}$) resp. ($\text{3b}$), which form exclusively the phenols ($\text{4}$) resp. ($\text{6}$) after oxidation with 3-chloroperbenzoic acid in the presence of 3,5-dimethoxyaniline ($\text{7a}$).     

Synthesis of enantiomerically enriched atrolactic acid and other α-hydroxy acids

The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid ($\text{2a}$, $\text{2b}$; $\text{3a}$; $\text{10a}$, $\text{10b}$) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-$\text{5}$,$\text{7}$,$\text{9}$, (R)(–)-$\text{13}$).     

Dependence of transmission of conjugation through cyclopropane ring into vinyl group on electron demand of substituent

The placement of a methoxycarbonyl or a cyano group on the cyclopropane ring in spiro-vinylcyclopropanes ($\text{7a}$, $\text{7b}$) causes a drain of electrons from the vinyl group through the ring into the electron demanding substituent, precluding their [2+2]cycloaddition with TCNE but not with the stronger electrophilic olefin CSI ($\text{7}$ → $\text{8}$), whereas the placement of a hydroxymethyl group renders the vinyl group reactive toward TCNE ($\text{9}$ → $\text{13}$).     

Fluorinated chromenes 1: 2,2,2-trifluoroethoxy precocene analogs and their corresponding 3,4-epoxides

Preparation of potential insect antijuvenile hormone agents 2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2H-chromene ($\text{3a}$), 6-methoxy-2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2$\text{H}$-chromene ($\text{3b}$) and 7-methoxy-2,2-dimethyl-6--(2,2,2-trifluoroethoxy)-2$\text{H}$-chromene ($\text{3c}$) and the corresponding 3,4-epoxides $\text{5a}$ and $\text{5b}$ is reported.     

A new synthesis of spirobenzylisoquinolines. Analogues of sibiricine and corydaine

The reduction product of dehydrocordrastine, $\text{6}$, with di-isobutylaluminum hydride spontaneously rearranged to the spirobenzylisoquinolines $\text{7a}$ and $\text{7b}$, analogous to the alkaloids sibiricine ($\text{5a}$), corydaine ($\text{5b}$), and yenhusomidine ($\text{5c}$).     

Reaction between nucleoside base residues and the phosphorylating agent derived from 1-hydroxybenzotriazole and 2-chloroprenyl phosphorodichloridate

In the presence of 1-methylimidazole, 2-$\text{N}$-acyl guanine (as in $\text{4a}$), thymine (as in $\text{5a}$) and uracil (as in $\text{5b}$) residues react readily with the phosphorylating agent derived from 2-chlorophenyl phosphorodichloridate ($\text{1a}$) and 1-hydroxybenzotriazole.     

Acid-catalysed reactions of 3,5-dialkyl-spiro[2.5]Octa-2,5-dien-4-ones

Acid-catalysed ring opening of the spirodienones ($\text{2a}$) and ($\text{2b}$) using p-toluene-sulphonic acid affords the styrène derivatives ($\text{3a}$) and ($\text{3b}$), while treatment with acetic anhydride/H₂SO₄ affords the furan derivatives ($\text{4a}$) and ($\text{4b}$).     

Conjugative cycloaddition of N-chlorosulfonyl isocyanate across vinylcyclopropane system. A new pathway towards macro-heterocycles

trans- -Isopropenyl-4-methylene-spiro[2.x]alkanes ($\text{4a}$ and $\text{4b}$) react at 0°C with CSI to give as major products the trans bicyclic cycloazanondienones ($\text{12a}$-$\text{12b}$) and as the minor products bicyclodihydro-azepinones ($\text{11a}$ and $\text{11b}$), and the respective cis isomer of bicyclic cycloazanondienones ($\text{13a}$ and $\text{13b}$).     

The vinylketene acetal route to aklavinone and 11-deoxydaunomycinone

11-Deoxyanthracyclinone precursors $\text{6a}$ and $\text{6b}$ have been prepared regiospecifically by the reaction of bromojuglone methyl ethers $\text{4a}$ and $\text{4b}$ with vinylketene acetal $\text{5}$, prepared from the Hagemann's ester ketal $\text{7a}$.     

The resolution of racemic 2-alkyl-1-aminocyclopropane-1-carboxylic acids

Practical procedures for the resolution of racemic modification of (1$\text{R}$, 2$\text{S}$)-and (1$\text{S}$, 2$\text{R}$)-1-amino-2-ethylcyclopropane-1-carboxylic acid $\text{1a}$,$\text{b}$,(1$\text{R}$, 2$\text{S}$)- and (1$\text{S}$, 2$\text{R}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{2a}$,$\text{b}$, and (1$\text{R}$, 2$\text{R}$)- and (1$\text{S}$, 2$\text{S}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{3a}$,$\text{b}$ are described; the structures as $\text{1a}$,$\text{2a}$, and $\text{3a}$ were confirmed by X-ray-crystallographic methods.     

Stereoselektive synthese von α-glucosiden mit 1,1′ -diacetal-struktur

Reaction of ($\text{1b}$) and ($\text{1d}$) with the acetal ($\text{2a}$) in presence of trimethylsilyl trifluoromethanesulfonate at ?70° C gives the α-glucosides ($\text{3a}$) and ($\text{4a}$), whereas ($\text{1a}$) and ($\text{1c}$) lead to the β-glucosides ($\text{4c}$) and ($\text{4b}$). At 0° C reaction of ($\text{1a}$) with the acetals ($\text{2b-g}$) gives exclusively the α-glucosides ($\text{3b-g}$).     

Competition entre substitution nucleophile et reduction chez les bromo-9 anthracenes dans l'action des anions phenate et methylate : Application à la mono-deutériation spécifique en méso en série anthracénique

Treatment of meso-substituted 9-bromoanthracenes bearing no hydrogen in the α position with potassium phenoxide in DMF gives rise to a competition between nucleophilic substitution and reductive dehalogenation. Derivatives carrying electron attracting groups, 1c (Br), 1e (CN) and 1f (NO₂), react essentially by substitution leading to phenolic ethers 2, whereas with non-activated bromides, 1a (H), 1b (C₆H₅) and 1d (OC₆H₅), the main reaction is a reduction to anthracenes 3 which should arise from an electron transfer.A reduction of 9-bromoanthracene into anthracene is also observed with sodium methoxide and it is shown, by labelling, that this one must result from a hydride transfer from methoxide. It may be applied to the specific meso-monodeuteriation of various anthracenic derivatives.     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.     

Addition conjuguee d'equivalents d'acyles aux cyclohexen-2 ones et a la Δ1(9) octalone-2: Synthese de dicetones 1–4.

The synthesis of 3-acetylcyclohexanones $\text{11}$, $\text{12}$, $\text{13}$ has been realized by conjugate addition of lithiated cyanohydrin ether $\text{1a}$ to 2-cyclohexenones $\text{2}$, $\text{3}$, $\text{4}$ in THF-HMPA, even if 3-substituted. 3-benzoylcyclohexanones $\text{14}$, $\text{15}$, $\text{16}$ are obtained from $\text{1b}$ and $\text{2}$, $\text{3}$, $\text{4}$ in THF with excellent yields.     

Amino substituted 1-oxa-3-azabutatrienium salts: preparation, structure and reaction with carbonyl compounds

N,N-Dimethylformamide ($\text{4a}$) and N,N-dimethylpivalamide ($\text{4b}$) react with carbonyl chloride isocyanate ($\text{5}$) in the presence of antimony pentachloride to afford the amino substituted 1-oxa-3-azabutatrienium hexachloroantimonates $\text{6a}$,$\text{b}$. An X-ray diffraction analysis of $\text{6a}$ confirms the proposed structure. The heterocumulenes $\text{6a}$,$\text{b}$ react with aldehydes, ketones and tertiary carboxamides to give the amino substituted 2-azaallenium salts $\text{13a}$-$\text{O}$ in high yields.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

2-cyano Δ3 piperidines vi1 : a general method for the stereoselective synthesis of cis and trans 2,6-dialkylpiperidine alkaloids

The cis 2,6-dialkylpiperidine alkaloid (±) dihydro-pinidine $\text{7b}$ and the trans alkaloid (±) solenopsin A $\text{5a}$ were synthesized from a common α-aminonitrile synthon $\text{1}$. The key step in this synthesis was the stereoselective reductive decyanation of the 1-benzyl-2cyano-2′, 6-dialkylpiperidines $\text{3a}$ and $\text{3b}$.     

Synthesis of bicyclo[6.2.2] bridgehead dienes

Bicyclo[6.2.2]dodecadienes ($\text{2}$), ($\text{3a}$), and ($\text{3b}$) having two bridgehead double bonds were synthesized by the pyrolysis of the acetate ($\text{1}$).     

Backbone rearrangements of methyl (-)-kaur-9(11)-en-19-oate and its epoxide: structures of two diterpenes of a new skeletal type

cleavage of the epoxide ($\text{2}$) of methyl (-)-kaur-9(11)-en-19-oate ($\text{1b}$) with boron trifluoride-ether in benzene and in acetic anhydride yielded ($\text{3a}$) and ($\text{3b}$), respectively. On epoxidation with $\text{m}$-chloroperbenzoic acid in the presence of $\text{N}$-nitrosomethyl urea, ($\text{1b}$) suffered a backbone rearrangement to form ($\text{6}$).     

Acid catalyzed isomerization of bicyclic alkenes: a facile betweenanene synthesis

Isomerization of $\text{cis}$-bicyclo[10.8.0]eicos-1(12)-ene ($\text{1a}$) and $\text{cis}$-bicyclo[10.10.0]docos-1(12)-ene ($\text{1b}$) to [10.8]- and [10.10]betweenanene ($\text{2a}$ and $\text{2b}$) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 $\text{2a}$/$\text{1a}$ and 95/5> $\text{2b}$/$\text{1b}$).