Cyclisation d'amides β-alleniques en dihydro-3,6 1H-pyridones-2.

Cyclisation of β-allenic amides, in the presence of a catalytic amount of silver tetrafluoroborate, leads to 3,6-dihydro-2(1H)-pyridones.     

Synthese en une etape d'α-alcoxyhydrazides,de derives d'α-aminoacides et d'α-hydroxyacides a partir des α-halogenohydrazides. Etude du mecanisme de la reaction.

α-halohydrazides react with nucleophiles under basic conditions to give α-functionalized hydrazides. We have shown that this reaction is not a direct nucleophilic substitution of the halogen but more likely proceeds through the formation of an aziridinone intermediate which then undergoes nucleophilic ring opening.     

Synthesis and Crystal Structure of 4-tert-Butyl-6-（4-chlorophenyl）-3,6- dihydro-2H-1,3-thiazin-2-iminium Chloride

The title compound, 4-tert-butyl-6-（4-chlorophenyl）-3,6-dihydro-2H-1,3-thiazin- 2-iminium chloride （C14H18C12N2S）, has been synthesized by the reaction of 1-（4-chlorophenyl）- 4,4-dimethylpent-1-en-3-one with thiourea, and its crystal structure was determined by single- crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P211c with a = 16.3064（11）, b = 9.4471（6）, c = 11.2626 （8）A, β = 108.400（1）°, Z = 4, V = 1646.28（19） A^3, Mr = 317.26, Dc = 1.280 g/cm^3, S = 1.078,μ = 0.510 mm^-1, F（000） = 664, the final R = 0.0514 and wR = 0.1412 for 3210 observed reflections （I 〉 2σ（I））. The thiazine ring system displays a twisted boat conformation, and three N-H,..Cl hydrogen bonds exist in the crystal. The combination of two N-H...Cl hydrogen bonds generate an R2^1 （6） ring.     

Reactivite SRN1 d'(α-nitroalkyl)-1 imidazoles: Synthese d'imidazoles alcoyles en position 1 par des chaines ramifiees et fonctionnalisees.

Gem-nitro imidazolyl alkanes reacting under S_RN1 conditions undergo nitro group replacement by variously substituted nitronates to give imidazoles carrying on position 1 tertiary alkyl chain R₁R₂CCNO₂(R₃R₄), the nitro group of which is easily replaced by H.     

Rearrangements de dihydro-2,3 benzo-b furannes α vinyliques en milieu acide : acces a des benzo-b furannes et 2h-benzo-b pyrannes

Neighbouring alkene group participation, resulting in isomerization, has been studied in reactions of some 2,3 dihydrobenzofurans with hydrobromic acid (in acetic acid) and with paratoluene sulfonic acid (in benzene). It was found that these 2-vinyl cyclic ethers afford benzo-b furans and Δ 3-chromenes ; the ratio of five-to six menbered ring products depending upon the reaction conditions and upon the number of methyl groups at the double bond.     

Synthesis of the naturally occurring naphtho-z.sfnc;2,3-bz.sfnc;pyran-5,10-quinones α-caryopterone,dihydro-α-caryopterone and their isomers 6-hydroxy-dehydro-α-lapachone and 6-hydroxy-α-lapachone

Isomeric 6- and 9-hydroxy-naphtho-z.sfnc;2,3-bz.sfnc;pyran-5,10-quinones were synthesised by alkylation-cyclisation of 2- and 3-hydroxyjuglone in a single step and can be distinguished by UV-visible spectra in the presence of additives and ¹HNMR.     

Interactions intramoleculaires—XXXI. Etude vibrationnelle des conformères de chloro-4 et de cyano-4 cyclohexénes alkylés en 3

Infrared and Raman spectra in the liquid state of 3-R, 4-X cyclohexenes (R = CH₃, (CH₃)₃C; X = CN,Cl) and their d₁-(4) and d₃-(3,6,6) isotopic modifications, Raman spectra of some low temperature crystallised compounds, vibrational spectra in the solid state of cis and trans 1-acetoxy 3-t-butyl 4-cyano cyclohexenes, were studied.The frequencies of cyclohexenic skeleton modes below 900 cm⁻¹ and the frequencies of deformation modes involving the CCN bond or stretching νCCl vibration of the different conformers were assigned. In the cis and trans 1-acetoxy 3-R 4-cyano cyclohexenes (respectively in the e′a and e′e conformations), the positions of the 627 cm⁻¹ δ_ax and the 538 cm⁻¹ δ_eq deformation vibrations agree with the assignments proposed for the other cyano derivatives.     

Ring opening of dihydro-2-pyridones and intramolecular Diels–Alder reactions

A new ring-opening reaction of 5,6-dihydro-2-pyridones was discovered. Compounds 1 and 7 were converted to the dienoic amides 2 and 8 by reaction with sodium hydride at room temperature. N-Allylation of compounds 2 and 8 followed by IMDA reaction provided the cis-fused hexahydro-1-indolones 5 and 10, respectively. Treatment of compounds 5 and 10 with DBU in refluxing ethyl acetate gave the conjugated products 6 and 11, which were further transformed to the amides 12–15. The phenylthio group of compound 11 was substituted by a methyl group to give product 16.     

Cyclic acetal formation between 2-pyridinecarboxyaldehyde and γ-hydroxy-α,β-acetylenic esters

A new transformation between 2-pyridinecarboxyaldehyde and γ-hydroxy-α,β-acetylenic esters to form highly functionalized cyclic acetals was discovered. This transformation proceeds under very mild conditions without any additives and is promoted by the basic nature of the pyridine ring.     

Réactions d'acylation sous irradiation micro-onde. II. Acylation d'éthers aromatiques

Acylation of aromatic ethers has been carried out under microwave irradiation, using rapid conditions (short reaction time and without temperature control) and in the presence of various catalysts, metallic chlorides, oxides (mainly iron derivatives), or triflates. For the benzoylation of anisole, the rise in temperature as a function of time is reported and connected to the efficiency of catalysts: the most active of them induce the largest temperature gradients. It is shown that microwaves have a specific interaction with the arylketone produced and especially with its catalyst-complexed form. However, a microwave nonthermal effect has not been observed, either for the yield or for the isomeric ratios of various products.     

Potassium Ferricyanide Mediated Cyclisation of 2′-Hydroxychalcones to Flavanones Using Phase Transfer Catalysis

Flavanones have been synthesised by cyclisation of 2′-hydroxychalones with potassium ferricyanide using phase transfer catalysis.     

Studies on structurally simple α,β-butenolides: VII. An easy entry to γ-thiomethyl- and γ-aminomethyl-α, β-butenolides

The reaction of the dilithium salt of phenylselenoacetic acid with a variety of glycidyl substrates yields 5-heteromethyl-3-phenylseleno-tetrahydrofuran-2-ones. Selective oxidation of the selenium atom allows the preparation of 5-thiomethyl- and 5-aminomethyl-2-(5H)-furanones.     

Reaction of γ-Sultines with Electrophilic Reagents. 1. Bromination of 3,5-Diaryl-1,2-oxathiolane 2-Oxides

The effects of the nature of the aryl substituents and the reaction conditions on the bromination of 3,5-diaryl-1,2-oxathiolane 2-oxides (-sultines) have been studied. The possible mechanisms for the bromination of the -sultines are discussed on the basis of the experimental data.     

Reactions of γ-Sultines with Electrophilic Reagents. 3. Chlorination of 3,5-Diaryl-1,2-oxathiolane 2-Oxides

The influence of the nature of the aryl substituents and the reaction conditions for the chlorination of 3,5-diphenyl-1,2-oxathiolane 2-oxide and 3,5-bis(4-methoxyphenyl)-1,2-oxathiolane 2-oxide have been studied. Possible mechanisms for the chlorination of -sultines are discussed.     

Synthèse Et Cyclisation De Carboxylsulfamides Dérivés D'amines Et D'α-Hydroxyesters. Éavaluation De L'Activité Bactéeriostatique

Abstract

Les carboxylsulfamides sont obtenus à partir de l'isocyanate de chlorosulfonyle, d'amines primaires et d'α-hydroxyesters. Après réduction alcaline, ces carboxylsulfamides sont cyclisés dans les conditions de la réaction de Mitsunobu pour conduire aux N-sulfamoyloxazolidinones chides avec des rendements élevés.

The synthesis of carboxylsulfamides was carried out starting from chlorosulfonyl isocyanate, primary amines and α-hydroxyesters. After reduction, the carboxylsulfamides were cyclised under Mitsunobu conditions giving N-sulfamoyloxazolidinones in good yields.     

Thermal ene reactions of methyl 3,3,3-trifluoro-2-R-sulfonyliminopropionates. Synthesis of γ,δ-unsaturated derivatives ofα-amino α-trifluoromethylcarboxylic acids

Thermal ene reactions of methyl 3,3,3-trifluoro-2-methanesulfonyliminopropionate and methyl 2-benzenesulfonylimino-3,3,3-trifluoropropionate with terminal alkenes afford derivatives of ,-unsaturated -amino -trifluoromethylcarboxylic acids in one step.     

Acetals of γ-oxo-α,β-unsaturated esters in nitrone cycloadditions. Regio- and stereochemical implications

Several acetals of γ-oxo-α,β-unsaturated esters have been prepared, mainly from enantiopure C₂-symmetric diols, and their 1,3-dipolar cycloaddition to 2,3,4,5-tetrahydropyridine 1-oxide has been studied. All the reactions showed complete regioselectivity and a high preference for the endo approach of the reactants in the transition state. The enantiopure acetals derived from (cis,cis)-spiro[4.4]nonane-1,6-diol gave the highest diastereofacial selectivity.