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 $\text{10}$.     

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.     

Synthesis of erythrinin A,a naturally occurring pyranoisoflavone

Erythrinin A ($\text{10}$) has been synthesised by the oxidative rearrangement of dihydropyranochalcone $\text{1}$ with thallium(III) nitrate (TTN) in trimethyl orthoformate (TMOF) to the dimethyl acetal $\text{2}$, followed by cyclisation to $\text{3}$, demethylation to $\text{6}$ and dehydrogenation. Compound $\text{10}$ could also be obtained from chalcone $\text{4}$ on similar rearrangement followed by cyclisation, demethoxymethylation and dehydrogenation. In another route, chalcone $\text{7}$ was oxidatively rearranged with TTN in TMOF, to $\text{8}$ which on treatment with HCl yielded $\text{10}$.     

Directing and stabilizing effects of substituted acetylenes in heterocyclisation: Efficient synthesis of pyrrolizidine alkaloids

($\text{+}$-Trachelanthamidine and ($\text{+}$-isoretronecanol have been synthesized via reductive cyclisation of the phenylthioacetylene imid $\text{5}$.     

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.     

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.     

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.     

The unexpected intramolecular C-arylation of 2-0-benzylated cyclic sugar derivatives: a useful 1,2-cis-C-glycosylation reaction

Upon treatment with tin(IV) chloride, perbenzylated glycofuranosyl acetates such as 3 or 6 undergo an unusual, intramolecular α-$\text{C}$-arylation resulting from the internal Friedel-Crafts alkylation of the 2-$\text{O}$-benzyl substituent.     

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.     

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 ($\text{1}$).     

Synthesis of (+) dictyopterene a constituent of marine brown algae and (+) dictyopterene C′ by chirality transfer of optically active allylic benzoate with palladium (O) catalyst.

The first enantioselective syntheses of (+) dictyopterene A $\text{1}$ and (+)dictyopterene C′ were reported. The key reaction was based on palladium promoted cyclisation of chiral allylic benzoate $\text{5}$ with transfer of chirality (anti attack of the palladium with respect to the leaving group) to give optically active vinylcyclopropane $\text{7}$ with (R) configuration which contains proper functionality for further elaboration into $\text{1}$ and $\text{3}$     

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 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).     

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.     

Stereochemical control by remote substituents in α-acyliminium olefin cyclisations

Stereoselective cyclisation of lactams $\text{1}$-$\text{4}$ in HCOOH leads to enantiomeric heterocycles $\text{5}$-$\text{8}$ in excellent yields.     

Synthesis and intramolecular cyclisation of ortho-hydroxy-2,3,3,3-tetrafluoropropiophenone. Formation of 3-fluoro-4-hydroxycoumarin

Acidic hydrolysis of 1-(o-methoxyphenyl)pentafluoropropene $\text{1}$ gave o-hydroxy-2,3,3,3-tetrafluoropropiophenone $\text{2}$ and o-methoxy-2,3,3,3-tetrafluoropropiophenone $\text{3}$. Compound $\text{2}$ when treated with aqueous potassium hydroxide or methanolic sodium methoxide gave 3-fluoro-4-hydroxycoumarin $\text{4}$. Structure of $\text{4}$ has been established by spectral means and some chemical reactions. The cyclisation mechanism of $\text{2}$ is discussed.     

A photochemical approach to protoberberine alkaloids

Photochemical cyclisation of methoxy-substituted $\text{N}$-(1,2,3,4-tetrahydroisoquinolin-2-ylmethyl)phthalimides and subsequent treatment of the photoproduct with aqueous acid leads to oxygenated compounds with the protoberberine skeleton.     

Total synthesis of (±)-alliacolide

A total synthesis of the unique epoxy-lactone alliacolide (3), featuring a novel, stereoselective intramolecular radical cyclisation onto an enolic double-bond, $\text{viz}$ (13) → (14), as a key step, is described.     

Fluorocarbon derivatives of nitrogen. Part VII [1]. Reaction of N-iminopyridinium ylide with perfluoro-1-azacyclohexene,perfluoro-2-azapropene,and perfluoroacetonitrile

The novel ylides (II) and (III) have been obtained $\text{via}$ treatment of perfluoro-1-azacyclohexene and perfluoro-2-azapropene, respectively, with $\text{N}$-iminopyridinium ylide (I) generated $\text{in}$$\text{situ}$ from $\text{N}$-aminopyridinium iodide and anhydrous potassium carbonate in methylene chloride. A mixture of the $\text{s}$-triazolo[1,5-$\text{a}$]pyridine (IV) and a compound thought to be its dihydro-analogue (V) were isolated following attack on perfluoroacetonitrile by the parent ylide (I); the former product was also prepared by heating 1,2-diamino-pyridinium iodide with trifluoroacetic anhydride.     

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.