Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno-fluorènes,XIX Dérivés tétraméthylés du trans-fluorénaphène et du trans-fluorénacène

By condensation of isophthaloyldichloride resp. of terephthaloyldichloride with 4-bromo-1,2-xylene according Friedel-Crafts, followed in each case by a double cyclisation and a final reduction, the 2,3,9,10-tetramethyl-7,12-dihydro-indeno[1,2-a]fluorene resp. the 2,3,8,9-tetramethyl-6, 12-dihydro-indeno[1,2-b]fluorene are synthesized.     

Composés hétérocycliques à partir (testers cyaniques. 4. Synthèse de nouvelles aroxy-2 quinazolinones-4

The cyclisation of ethyl anthranilate and ethyl N-methyl-anthranilate with aryl cyanates, catalyzed by benzoic acid, provides a simple and general method in high yields for the synthesis of 2-aroxy-4-quinazolinones and 2-aroxy-l-methyl-4-quinazolinones.     

Fluorénacènes et fluorénaphènes synthèses dans la série des indéno-fluorènes,XVII. Dérivés méthylés du cis-fluorénacène,du trans-fluorénacène et du trans-fluorénaphène

By condensation of the chlorides of the three 9-oxo-fluorene-2-, -3-, and -4-carboxylic acids with 4-bromo-1,2-xylene on one side, and of the chlorides of o-bromobenzoic acid, 2-bromo-4-methyl-benzoic acid and 2-bromo-4,5-dimethyl-benzoic acid with fluorene, 2-methylfluorene and 3-methylfluorene on the other side, followed by direct or indirect cyclisation and by final reduction, several new methyl derivatives of the indenofluorenes I, II and IV are synthesized.     

Action des hydrazines sur les acétyl-4 chloro-5 (ou 3) méthyl-3 (ou 5) pyrazoles: Formation d'une pyrazolo[3,4-b]quinoléïne,d'hydrazones et de cétazines

The cyclisation of 4-acetyl-5(or 3)-chloropyrazole hydrazones into pyrazolo[3,4-c]pyrazoles does not proceed when the pyrazole is a N-methylated derivative or when the hydrazone is a phenylhydrazone. Instead of 1-azapentalene derivatives, a new pyrazolo[3,4-b]quinoline and several hydrazones and ketazines have been isolated.     

Deux types de participation π lors de l'hydrolyse des diazocétones γ, δ-insaturées par des acides aqueux et des superacides. L'ion oxo-5-norbornyle-2

γ, δ-Unsaturated diazoketones undergo acid catalysed hydrolysis accompanied by cyclisation; the latter is favoured by suitable geometry (cyclopentenes) and by substitution by methyl groups. If both are present, rate enhancement by anchimeric assistance has been observed. Hydrolysis of 4-diazoacetyl-cyclopentene ( 1 ) yields a product mixture similar to that formed during solvolysis of 5-oxo-norbornyl-2-endo brosylate (23) and quite different from that of the exo isomer. The results are interpreted in terms of a common intermediate, the 5-oxo-2-norbornyl carbonium ion. Solvent participation in the transition state, i. e. partial S_N 2 character, is implied by the entropies of activation and by the action of an added nucleophile (Br^?). In superstrong acids, a different type of cyclisation takes place, involving the carbonyl oxygen and the protonated C? C double bond and forming tetrahydropyrane derivatives.     

Radical cyclisations of methylenecyclopropyl azetidinones—synthesis of novel tricyclic β-lactams

Addition of lithium bis(methylenecyclopropyl)cuprates to acetoxy azetidinones gives methylenecyclopropyl azetidinones, which can be converted to various radical cyclisation precursors. Attempted 4-exo cyclisation of 3 led only to reduced product, while cyclisation of 5, using CuCl/bipy, gave a carbacephem, via a 5-exo cyclisation, but in low yield. Cyclisation of 6 and 7, however, gave novel tricyclic β-lactams, as the result of 7-endo cyclisation, in good yield, and a cyclisation of bromide 23 led to the tricyclic β-lactam 24, via a radical cascade sequence.     

Recherches en série triazépine-1,2,4: II — Etude de la réaction de l'acétylacétate d'éthyle avec les diamino-3,4 oxo-5 dihydro-4,5 triazines-1,2,4

The reaction of 3,4-diamino-5-oxo-4,5-dihydro-l,2,4-triazine or its 6-methyl or 6-phenyl substituted derivatives and ethyl acetoacetate gave three compounds: 4,7-dioxo-9-methyl-1,4,6,7-tetrahydro-as-triazino[4,3-b]-1,2,4-triazepine in poor yield, isomeric 4,9-dioxo-7-methyl-1,4,8,9-tetrahydro-as -triazino[4,3-b]-1,2,4-triazepine and by competitive cyclisation, 2-methyl-7-oxo-3,7-dihydro-s-triazolo[3,2-c]-1,2,4-triazine. By condensation of 3-methylamino-4-amino-5-oxo-4,5-dihydro-1,2,4-triazine with ethyl acetoacetate, the formation of 4,9-dioxo-7,10-dimethyl-4,8,9,10-tetrahydro-as-triazino[4,3-b]-1,2,4-triazepine was strongly favored.     

Synthèse du tétraéthoxycarbonyl-1,1,6,6-cyclodécadiyne-3,8

A cyclisation of 1-bromo-5,5,10,10-tetraethoxycarbonyl-2,7-decadiyne ( 9b ) using NaH in dilute solution gives 1,1,6,6-tetraethoxycarbonyl-cyclodeca-3,8-diyne ( 8 ) in 17,6% yield. 9b is prepared by condensation of 1,1,6,6-tetraethoxycarbonyl-3-hexyne with 1,4-dibromo-2-butyne.     

Le mécanisme de la réduction polarographique des dérivés ditosyloxylés et son implication en électrochimie préparative

The cleavage of a single SO₂? O bond occurs during the polarographic reduction of a tosyloxy group (p? CH₃C₆H₄SO₂O = TsO) in aprotic medium and intramolecular cyclisation may ensue when a second TsO group is present on the same molecule. The polarographic behaviour of aliphatic ditosyloxy derivatives is discussed on the assumption that oriented vicinal derivatives at the interface assume a conformation which resembles the geometry of the transition state for an intramolecular elimination with anchimeric assistance of one of the tosyloxy groups. This situation favours the electron transfer, whereas the same geometric requirements hinder the intramolecular interaction of the TsO groups of the oriented non-vicinal derivatives. This interpretation agrees well with the fact that the large scale electrolysis of vicinal ditosyloxy derivatives give much higher yield of cyclic ethers than the higher homologues. It is also shown that intramolecular interaction between TsO groups can occur through an intervening double bond in a non-vicinal derivative.     

Synthesis of Glycoborine,Glybomine A and B,the Phytoalexin Carbalexin A and the β‐Adrenoreceptor Antagonists Carazolol and Carvedilol

We describe a regioselective synthesis of 4‐ or 5‐substituted carbazoles by oxidative cyclisation of meta‐oxygen‐substituted N‐phenylanilines. Using the regiodirecting effect of a pivaloyloxy group, we prepared 4‐hydroxycarbazole, a precursor for the enantiospecific synthesis of the β‐adrenoreceptor antagonists (?)‐(S)‐carazolol ( 5 ) and (?)‐(S)‐carvedilol ( 6 ). Regioselective palladium(II)‐catalysed cyclisation of different diarylamines led to total synthesis of glycoborine ( 7 ) and the first total syntheses of the phytoalexin carbalexin A ( 8 ), glybomine A ( 9 ) and glybomine B ( 10 ). For glybomine B ( 10 ), a 5‐hydroxycarbazole was converted into the corresponding triflate and utilized for introduction of a prenyl substituent.     

Nouvelle méthode d'accès aux benzo[h]furo[3,2-c]quinoléines,analogues isostériques des benzo[c]phénanthridines

A convenient synthesis of the benzo[h]furo[3,2-c]quinoline ring is reported. Hydrogenation of dienic adducts 5 gives comppounds 6. Successive pyrolysis and alcaline hydrolysis of 6 provide diacids 9 which in the presence of anhydrous ammonium acetate and acetic acid undergoes intramolecular cyclisation to give benzo[h]furo[3,2-c]quinolone derivatives 12. The modulation of the 7-carboxy group and introduction of amino groups in the 6 position are then realized.     

Isomérisations en chimie des sucres. II Fermetures de cycles par attaque nucléophile intramoléculaire sur des carbones sp2 à caractère électrophile: Furannoses hybridés sp2 en C3

When heated with one equivalent of H₂O, the 1,2: 5,6-di-O-isopropylidene-α-D-ribo- and -xylo-hexofuranos-3-uloses loose one molecule of acetone and yield the 3, 6-anhydro-1, 2-O-isopropylidene-α-D-ribo- and -xylo-hexofuranos-3-ulose ketohydrols. The carbonyl group of the starting material seems to provide some kind of intramolecular electrophilic assistance to the hydrolysis of the 5, 6-O-isopropylidene group. When the oxygen of the carbonyl group is replaced by cyanomethylene, an analogous cyclisation takes place under base catalysis, provided that C6 bears a free hydroxyl group.     

Réactions de substitution nucléophile de l'hydroxyurée. Synthèse et étude des oxa-6 dihydrouraciles

Hydroxyurea, an N-protected hydroxylamine, reacts with α-bromoesters to give α-ureidoxyesters. Some of these have been isolated. Their cyclisation is a synthetic route to 6-oxadihydrouraciles which structure has been well established by means of physicochemical methods. Especially, ¹³C nmr spectroscopy has been used to show only the presence of the diketone tautomeric form.     

Synthèses dans la série des bis-indéno-fluorènes,IX. Le dihydro-13,15-7H-bis-indéno[2.1-b; 2′.1′-h]fluorène et son dérivé méthylé en position 6

By condensation according Ullmann of 2-iodo-9-oxo-fluorene with 3-bromo-2-cyano-9-oxo-fluorene, followed by cyclisation and reduction, the new linear 13,15-dihydro-7H-diindeno[2.1-b; 2′.1′-h]fluorene (III) is synthesized in 3 steps. The 6-methyl-derivative of II is also obtained in a similar way.     

Synthèse électrochimique du cycle époxydique. Communication préliminaire

The polarographic behaviour of ditosyloxy alkanes TsO(CH₂)_nOTs in aprotic medium suggests that intramolecular cyclisation takes place after reductive cleavage of a single SO₂? O bond at the dropping electrode. This hypothesis was verified by controlled potential electrolysis of the lower homologues at a mercury cathode. High yields of epoxy compounds are obtained by this method.     

Free radical cyclisation of enamides leading to biologically important γ-lactams

This review describes the free radical cyclisation of enamides using tributyltin hydride, manganese(III) acetate, copper(I) complexes or dichlorotris(triphenylphosphine)ruthenium(II). These cyclisations can proceed via either 4-exo or 5-endo pathways, to produce β- or γ-lactam products, respectively. In general, the reactions produce γ-lactams derived from an unusual (disfavoured) 5-endo-trig radical cyclisation. These results can be explained on the basis of a reversible cyclisation mechanism; the 4-exo cyclisation produces the kinetically favoured β-lactam while the 5-endo cyclisation produces the thermodynamically more stable γ-lactam.     

Analogues méso-hétérocycliques du dihydro-9,10 anthracène. XII — Sur quelques indoles dérivés de la dibenzo-p-dioxine

2-Aminodibenzo-p-dioxine undergoes facile condensation with different ω-bromoketones to give 2-aroylmethylaminodibenzo-p-dioxines, which undergo Möhlau-Bischler cyclisation under certain conditions. Some indolo[5,6-b] [1,4]benzodioxine were prepared by this method and their biochemical effect on the zoxazolamine hydroxylase in rats was studied.     

The cyclisation of the di- and tetra-aldehydes derived from sucrose with nitroalkanes.

Selective oxidation of sucrose (1) with lead tetra-acetate gave the dialdehyde (2), which underwent Fischer cyclisation with both nitromethane and nitroethane, to give disaccharides (7) and (10) respectively. Nitromethane cyclisation of the tetraaldehyde (5), produced from periodate oxidation of sucrose, gave 3-nitro-3-deoxy-α-D-glucopyranosyl 4-nitro-4-deoxy-β-D-heptulopyranoside (11) as the major product.     

Participation π dans la solvolyse des diazocétones primaires. Communication préliminaire

In the acid catalyzed hydrolysis of 5,6-unsaturated diazoketones of suitable geometry (Ib, IIb, IIIb, IVb, VIb), participation of the double bond in the reaction of the diazonium ion is proved (a) by the formation of cyclisation products, and (b) in some cases by the acceleration of the rate determining S_N2 substitution process. In the case of VIb the substitution step is so much accelerated that the pre-equilibrium protonation step becomes rate determining (evidence: inversion of the kinetic solvent isotope effect).     

Interactions intramoléculaires. XXVI—Constantes de couplage et hétérogénéités conformationnelles dans une série de R-3 et R-5 cyano-4 cyclohexènes deutériés (R=méthyl ou t-butyl)

For trans-3-R- and 5-R-1-acetoxy-4-cyanocyclohexene-6,6-d₂ the molar fractions of diequatorial conformers are 0.83 (3-methyl), 0.68 (5-methyl), 0.57 (3-tert-butyl) and 0.55–0.69 (5-tert-butyl). For the last two compounds the values of the coupling constants are in agreement with the hypothesis of an ee?aa equilibrium. For the cis isomers, the molar fractions of equatorial alkyl conformers are 0.76 (3-methyl and 5-methyl) and 1.0 (3-tert-butyl and 5-tert-butyl). The cis-1-acetoxy-3-tert-butyl-4-methoxycarbonyl-cyclohexene presents a conformational heterogeneity. The conformational free energy of the methyl group in position 4 has been evaluated as ?0.6 kcal mol^?1 (2.5 kJ mol^?1).