On the properties of some substituted α'-lithiated α(z), -butadienyl sulfides: cyclisations and rearrangements

The conditions for the preparation and cyclisation of the title compounds $\text{3}$ are described. The stability of the intermediate lithio-thiacyclohexenes $\text{4}$ is shown to depend on the reaction conditions and the substituents R¹-R⁴. The final products $\text{6}$, $\text{10}$ and $\text{7}$ arise from $\text{4}$ via a [1.4] sigmatropic rearrangement, a [1.3]prototropic shift followed by a [2.3] sigmatropic rearrangement, or the elimination of lithium methanethiolate respectively.     

Syntheses totales de la (+) iso β-peltatine

α-Hydroxyalkylation of a β-(alkoxy 3,4-methylenedioxy benzyl)-γ-butyrolactone ($\text{17}$ or $\text{25}$) with 3,4,5-trimethoxybenzaldehyde or syringaldehyde $\text{27}$, followed by cyclisation, afforded good yields of the corresponding (±) isopeltatines.     

Cycloaddition reactions of 2,3-didehydrothiophene generated by flow vacuum thermolysis of thiophene-2,3-dicarboxylic anhydride

Flow vacuum thermolysis (FVT) of thiophene-2,3-dicarboxylic anhydride ($\text{2}$) in the presence of 2,3-dimethylbutadiene ($\text{6}$) gives, in addition to 5,6-dimethylthianaphthene ($\text{9}$). small quantities of a dihydrodimethylthianaphthene ($\text{12}$) and another dimethylthianaphthene ($\text{13}$) which is probably also formed by dehydrogenation of $\text{12}$ with chloranil. The partial structures of these minor products are consistent with their being formed by a [2+2]-cycloaddition between $\text{6}$ and an intermediate aryne, 2,3-didehydrothiophene ($\text{1}$), followed by a rearrangement of the resulting adduct $\text{11}$ and dehydrogenation. FVT of $\text{2}$ in the presence of 2,5- ($\text{17b}$) or 3,4-dimethylthiophene ($\text{17c}$) also gave a mixture of the dimethylthianaphthenes ($\text{18}$$\text{22}$, $\text{23}$) which can be rationalized as arising by a [4+2]- and two [2+2]-cycloadditions of the aryne $\text{1}$ to the thiophenes $\text{17}$ with subsequent desulfurization. The lack of equilibration of the products $\text{18}$, $\text{22}$ and $\text{23}$, was demonstrated and their origin as a function of the structure and reactivity of the aryne $\text{1}$ discussed.     

Intramolecular cyclisation of α,β-epoxy-artemisia ketone

α,β-epoxy-artemisia ketone, $\text{2}$ undergoes intramolecular cyclisation by OM-DM yielding the tetrahydrofuran derivatives $\text{3}$ – $\text{6}$, while on treatment with BF₃,-etherate $\text{2}$ cyclises to the cyclopentanones $\text{8}$ and $\text{9}$. The structure of all products has been elucidated by spectral methods. The mechanism of the cyclisation reaction is discussed briefly.     

Efficient heterocyclisation via 2-aza-cope rearrangements of α-acyliminium intermediates. Formation of pyrrolizidines and somel thia-analogues

HCOOH-ring closures of OH-lactams $\text{7}$ possessing an allyl substituted alkene function solely afford pyrrolizidines $\text{8}$ and $\text{9}$ in high yield via 2-aza-Cope rearrangement and ensuing α-acyliminium cyclisation.     

The formation and subsequent cyclisation of novel hydroperoxides from a 1,4− and a 1,5-diene

The preparation of the unsaturated hydroperoxides ($\text{3}$,$\text{4}$,$\text{5}$,$\text{6}$ and $\text{7}$) by the sensitized photooxidation of the 1,4-diene($\text{1}$) and the 1,5-diene($\text{2}$) is described, together with the attempted free-radical cyclisation of these.     

Unprecedented rearrangements via allenes as π-participants in α-acyliminium ion cyglisations

Upon HCOOH reaction of ethoxylactams $\text{1a}$-$\text{1d}$ the terminally unsubstituted allenes $\text{1a}$ and $\text{1d}$ underwent a [3,3] sigmatropic rearrangement. The dimethyl allenes 1b and 1c afforded only products from an α-acyliminium ion cyclisation.     

Une synthese totale stereospecifique du (±) attenuol

α-Hydroxyalkylation of β-(3,4-methylenedioxy-benzyl)-γ-butyrolactone ($\text{3}$) with p-benzoxy benzaldehyde, followed by cyclisation, reduction of the lactone ring and removal of the benzyl group, afforded the lignan (±) attenuol ($\text{1}$).     

[O9,24] [2.1.2.1] metacyclophane-9-ene,a “twin cyclophane”, and its dehydrogenation products - synthesis structure determination and 1H-NMR-spectroscopy

The synthesis of [O⁹,24] [2.1.2.1]metacyclophane-9-ene and of its dehydrogenation products^the new pyrenocyclophanes $\text{8}$, $\text{10}$, $\text{11}$, and $\text{12}$, is described; their structures are discussed in connection with their ¹H-NMR-spectra.     

Synthese de N-(tetrazol-5-yl) azetidin-2-ones

The title compounds were obtained by addition of a glycine enolate to a N-(tetrazol-5-yl) imine followed by cyclisation. This route provided both the $\text{cis}$ and the $\text{trans}$ substituted azetidinones. The $\text{cis}$ compounds possessed improved antibiotic activity as compared to the $\text{trans}$ counterparts.     

Synthese de macrolides par methathese.

Two syntheses of macrolides $\text{via}$ olefin methathesis are presented. The first (A) involves preparation of ω-hydroxyacid $\text{6}$ or $\text{9}$ by metathesis followed by cyclisation, while the second (B) involves macrocyclic ring closure by metathesis of a ω,ω′diunsaturated ester $\text{12}$.     

Synthesis of a New Naturally Occurring 3-Phenyl-4H-1-Benzopyran-4-One

7-Hydroxy-8-methoxy-3-(3,4-methylenedioxyphenyl)-4H-1-benzopyran-4-one (1), a new isoflavone reported to occur in the aerial parts and roots of Tephrosia maxima has been synthesized by the oxidative rearrangement of 2′-hydroxy-3′-methoxy-4′-benzyloxy-3,4-methylenedioxychalcone (4) with thallium (III) nitrate (TTN) in trimethyl orthoformate (TMOF), followed by acid catalysed cyclization and debenzylation. It has also been synthesized by another method from 2,3,4-trihydroxy-3,4′-methylenedioxydeoxybenzoin; the hitherto unknown biisoflavone, 7,7′-dimethoxy-3′,4″,3″,4″-dimethylenedioxy-8,8′-biisoflavonyl ether was also formed during this method.     

Olefin metathesis in polycyclic frames 1. A new way to cis, syn, cis - tricyclopentanoids (acs-C11-triquinanes)

A novel olefin metathesis sequence permits ready access to functionalised $\text{cis}$, $\text{syn}$, $\text{cis}$-tricyclo [6.3.0.0^2,6] undecane based bis-enones. These bis-enones have been shown to undergo cage cyclisation in sunlight with remarkable ease and efficiency.     

Syntheses of trifluoromethylated diene derivatives through the claisen rearrangement of trifluoromethylated propargylic and allylic alcohols

3-Trifluoromethyl-2Z, 4E-dienoate ($\text{14}$) and the dienamide ($\text{10}$,$\text{11}$) were prepared through the Claisen rearrangement of trifluoromethylated propargylic and allylic alcohols.     

Molecular rearrangements of 5-azido substituted 1,2,3-triazoles

5-Azido-4-methoxycarbonyl-1-phenyl-1,2,3-triazole ($\text{8a}$) and its phenyl substituted derivatives $\text{8b}$,$\text{c}$ rearrange at 60–80°C to give tetrazolyldiazoacetates $\text{9}$, which have been isolated. When the reactions are allowed to go to completion, products derived from the diazo compounds are obtained; i.e. norcaradienes ($\text{10}$) from benzene solutions and imidazotetrazoles ($\text{12}$) from nitrite solutions. The latter decompose photochemically into diazacyclopentadienonimines ($\text{13}$). A kinetic study of the rearrangement $\text{8}$ → $\text{9}$ has been carried out and the mechanism (Scheme VI) is discussed in comparison with the Dimroth rearrangement.     

Synthesis of functionalised cyclopentanes by intramolecular radical-mediated cyclisations of terminal allenic ketones

Electrolysis of a series of terminal allenic ketones e.g. (7), (10), (17) and (21) is shown to result in intramolecular reductive cyclisation, through the $\text{exo}$-mode, producing five-membered rings, $\text{viz}$ (8), (9), (20) and (22) respectively, incorporating a bridgehead hydroxyl group. The unsaturated alcohols (8), (20) and (22), are also obtained when the allenic ketones (7), (17) and (21) are treated with sodium naphthalenide. By contrast treatment of (10) in the sodium naphthalenide gives a low yield ($\text{ca}$ 7%) of the isomeric indenol (11) by cyclisation through the $\text{endo}$-mode.Reductive cyclisations of the terminal acetylenic ketones (14) and (30) produce the corresponding unsaturated alcohols (26) and (31) respectively. Treatment of the alcohols (26) and (31) with catalytic selenium dioxide then provides the enediols (27) and (32) respectively, which make up the B/C ring systems of the novel marine natural products capnellenediol (1) and isoamijiol (2).     

The syntheses of polycyclic molecules containing b-carboline units by the photochemically induced ring closure of enamides

The syntheses of 5-methyl-5,8,9,14-tetrahydroindolo(2,3-$\text{c}$)indolo (2,3-$\text{g}$) quinolizin-6-one and 15-methyl-7,8,13,15-tetrahydroindolo ( 3,2-$\text{c}$) indolo(2,3-$\text{g}$)quinolizin-5-one from the photochemical cyclisation of i-methylene-2-(N-`methylindole-2'-carbonyl) 1,2,3,4-tetrahydro-B-carboline and 1-methylene-2- (N-`methylindole-3' carbonyl) 1,2,3,4,-tetrahydro-B-carboline are described. Attempts to prepare indolo(2,3-$\text{c}$)isoquinolines from the photochemical cyclisation of 2-benzamidoindoles were unsuccessful.     

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.     

α-acyliminium ion synthesis of elaeokanine B

Elaeokanine B has been synthesized utilizing the acid-catalyzed cyclisation of hydroxylactam $\text{9}$ as key step in the formation of the chloride $\text{10}$.