HMPA-Mediated conjugate addition of alkyl- and phenylthioallyl anions to cyclopentenone

One equivalent of HMPA induces 1,4-addition of the title anions predominantly through the $\text{α}$-position to cyclopentenone in THF at ?78°. In THF alone irreversible addition takes place to give mixtures comprising largely $\text{α}$ and $\text{γ}$-1,2 products.     

Zur deprotonierung von chloromethyleniminiumchloriden

Deprotonation of chloromethyleniminium chlorides ($\text{1}$, $\text{13}$) leads to cis-trans-isomeres 1,2-diamino-1,2-dichloro-ethenes ($\text{3a}$, $\text{3b}$ resp. $\text{14a}$, $\text{14b}$); their reactivity is described.     

Etude de l''addition des organomagnesiens satures et benzyliques aux enynes conjugues, simples et fonctionnels

Saturated and benzylic organomagnesium compounds are shown to readily undergo addition reactions with the conjugated enynes H$\text{C}\text{4}$$\text{C}\text{3}$C$\text{H}\text{2}$$\text{C}\text{1}$HCH₂R′, with R′ = alkyl, OH, OC₄H₉, NHC₂₅, N(C₂H₅)₂, by refluxing for several hours in benzene or toluene.This reaction leads to both υ-acetylenic compounds (1,2-addition) and β-allenic compounds (1,4-addition).     

Syntheses of PGJ2 type analogues: 16-hydroxy-11-oxo-Δ5,9,12,14-prostatetraenoic acid t-butyl ester and its related derivatives

PGJ₂ analogues, the title compound ($\text{8c}$) and its related derivatives ($\text{8a}$, $\text{8b}$), were synthesized $\text{via}$ the three-component coupling process involving 1,4-addition reaction of phenylsulfinylallylic carbanion ($\text{2}$′) to cyclopentenone derivative ($\text{1}$) followed by trapping the generated enolate with aldehyde ($\text{3}$).     

Reactions d'addition du tetrahydrofuranne sur les F-alkyl ethylenes,F-alkyl acetylenes et F-alkyl propynoates d'ethyle

The thermal behaviour of F-alkyl éthenes 1, F-alkyl acetylenes 2 and ethyl 3-F-alkyl propynoates 3 in tetrahydrofuran solvent was investigated. In refluxing solvent, one THF unit, reacting at its α-site, was added to the terminal unsaturated carbon of 1 and 2, and to the carbon bearing the F-alkyl group of 3; the reaction is regiospecific. Moreover, the monoadducts produced from 2 and 3 showed a strong stereoselectivity, leading respectively to E 2-(1,2-dihydryl 1-F-alkenyl)tetrahydrofurans and E ethyl 3-F-alkyl 3-(2-tetrahydrofuryl)-propenoates as the main products ($\text{cis}$-addition of THF to 2 and $\text{trans}$-addition to 3).     

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.     

Synthesis and physical properties of 6,12-diarylazuleno[1,2-b]azulenes

The structure of a minor dimer ($\text{2a}$) of 1-arylcycloheptatrienylidenethylene was determined by X-ray crystallography. Dehydration of $\text{2a}$ and $\text{2b}$ gave novel non-benzenoid aromatics---6,12-diarylazuleno[1,2-b]azulenes ($\text{3a}$ and $\text{3b}$), whose electronic and NMR spectral properties were reported.     

Stereochemistry of nucleophilic additions to hexafluoro-2-butyne

Base-catalysed additions of alcohols to F-2-butyne (1) give mainly products of $\text{trans}$-addition while $\text{cis}$-addition predominates in uncatalysed additions of alcohols carried out in a diluent. The stereochemistry of addition of diethylamine is very dependent on the solvent used and $\text{cis}$- or $\text{trans}$-addition may predominate. Stepwise and concerted mechanisms are advanced to account for these observations. Nucleophilic addition of sulphur to (1) gives F-tetramethylthiophene (68%) and hydration gives CF₃CH₂COCF₃ (91%).     

Directed metallations of 4-ethylidenetetronic acid and its derivatives as a synthetic entry to natural 4-oxy-2-furanones

Lithium diisopropylamide (LDA) removes the α-proton from the O-methyl tetronic acid (2$\text{b}$) leading to the vinylic carbanion (12), whereas treatment of the trimethylsilyl derivative (14) with LDA, followed by reaction with aldehydes gives products resulting from both γ? and ε-addition; the directed metallations provide access to a range of 4-oxy-2-furanone derivatives found amongst natural products.     

The clemmensen reaction of tigogenin. A reinvestigation

The reaction of tigogenin ($\text{1b}$) with amalgamated zinc yields tetrahydrotigogenin ($\text{2b}$) and the furostan $\text{3}$. While $\text{2b}$ undergoes acid catalyzed elimination to give the rearranged product $\text{7}$, $\text{3}$ spontaneously decomposes to a mixture of $\text{4}$ and $\text{5}$.     

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 ($\text{5c}$).     

Bicyclic aziridines as intermediates in the photolysis of polycyclic aromatic azides.

According to the subsequent treatment, azepines $\text{16}$, $\text{17}$, $\text{19}$ or 1,2-dihydro derivatives $\text{18}$ and $\text{20}$ are obtained in the photolysis in basic medium of β-anthracenic azides $\text{7b}$ and $\text{7c}$ and provide strong evidence for the intermediate formation of bicyclic aziridines.     

Conformation-specific photochemistry in the solid state

The unsymmetrical ene-dione $\text{1b}$ exists in solution as a mixture of two conformational isomers, A and B, in rapid equilibrium. Irradiation of $\text{1b}$ in this medium leads to four products, two from each conformer. In the solid state, however, compound $\text{1b}$ adopts a single conformation (A), and photolysis of crystals of $\text{1b}$ leads to a single product. The formation of one rather than two photoproducts in this instance is attributed to a unique solid state steric effect, termed steric compression.     

Singlet oxygenation of cycloheptatriene: isolation and characterization of the 1,2-dioxetane

Tetraphenylporphyrin-sensitized photooxygenation of cycloheptatriene afforded the 1,2-dioxetane ($\text{3a}$) in 9% yield, thus completing the set of possible cycloaddition products; the 1,2-dioxetane ($\text{3a}$) is the precursor to the benzaldehyde product, but not the (2+6)-cycloadduct ($\text{2a}$).     

Iridoids : on the synthesis and structure of specionin

Recently, structure $\text{8b}$ has been assigned to the iridoid specionin. In the present letter the total synthesis of $\text{8b}$ is described. Comparison of spectral data reveals that the final product is not identical with natural specionin. Therefore the original structural assignment of specionin must be revised.     

Studies in claisen rearrangement - novel thermal and mercuric trifluroacetate induced transformations of 2,4-di(N-aryl)amino-1,3,5-triazin-6yl-prop-2-y

The thermal rearrangement of 2,4-di(N-aryl)amino-1,3,5-triazin-6yl-prop-2-ynyl ethers $\text{1}$ yield a mixture of 6-methyleneimidazo(1,2-a)-1,3,5-triazine-4-one $\text{6}$ and 6-methylimidazo(1,2-a)-1,3,5-triazine-4-one $\text{7}$, whereas under the influence of mercuric trifluroacetate the ethers $\text{1}$ yield only $\text{6}$, at room temperature. Mechanisms invoking [3,3] sigmatropic rearrangement of ethers $\text{1}$ were proposed to account for the product formation.     

Chemistry of 4-membered cyclic nitrones (2, 3-dihydroazete 1-oxides); a novel one-step synthesis of N-acetoxy β-latams

2,3-dihydroazete 1-oxide $\text{1}$ reacts at room temperature with base, acid and lead tetraacetate to give the 5-hydroxyisoxazolidines $\text{4a}$ and $\text{4b}$, the 6H-1,2-oxazin-6-one $\text{7}$ and the N-acetoxy β-lactam $\text{8}$, respectively; the reaction with lead tetraacetate represents a simple one-step conversion of a 4-membered cyclic nitrone into a β-lactam.     

Conjugate addition of organolithium reagents to acrylanilide anions

Phenyllithium, $\text{n}$-butyllithium, and $\text{t}$-butyllithium were found to add to substituted acrylanilide anions to give the 1,4-addition products in fair to good yields.     

Adamantane rearrangement mechanisms. 1,2-trimethylenenorbornanes

Unexpected differences in the aluminium bromide-catalyzed rearrangement behaviour of 1,2-$\text{endo}$-trimethylenenorbornane ($\text{1}$) and its 1,2-$\text{exo}$-isomer ($\text{2}$) are interpreted. Isotopic labelling studies indicate that reversible abstraction of the tertiary 2-$\text{endo}$ hydride in $\text{2}$ does not occur. Instead, rearrangement to $\text{6}$ is favored. The label scrambling in the final product, adamantane ($\text{8}$), is attributed to degenerate isomerization in the proto-adamantyl precursor, $\text{7}$.     

Carbocyclic analogs of C-nucleosides: a key intermediate via a novel and efficient CC ring scission

Treatment of hydroxymethylene ketone $\text{6}$ with trimethylene dithiotosylate according to literature conditions,^3b led to the novel CC ring scission product $\text{7}$ in high yield; also, the hydroxide-initiated cleavage⁴ of $\text{1}$ gave the β-elimination product $\text{13}$ which underwent a highly stereospecific addition of diazomethane to provide $\text{15}$.