Reaction des nitrones avec les chlorures d'acides: action de chlorures d'aryl-sulfonyles et du chlorure de benzoyle sur des n-oxy (aryl-1 dihydro-3,4 isoquinoleines). Formation d'une isoquinoleine,d'un isocarbostyryle ou d'une indoline selon les conditions

Toluene-p-sulphonyl chloride, p-nitrobenzoyl chloride, and benzoyl chloride react with 1-aryl 3,4-isoquinoline N-oxide depending on the acidity of the medium, the nature of the substituent at C-1, and the nature of the acid chloride, to give an isoquinoline, an isocarbostyril (resulting from migration of the phenyl substituent at C-1), an indoline (resulting from migration of the phenyl moiety incorporated in the heterocycle), or the formation of an O-acyl hydroxamic acid. The maximum selectivity is obtained in an heterogeneous medium and is governed by the intermediate formation of an hydroxylated pseudo-base.     

Chiral Amine Catalyzed Reductive Aldol/Reductive Michael Addition Cascade Towards Enantioselective Synthesis of Benzannulated Diquinanes

Disclosed here an amine-catalyzed reductive aldol-condensation followed by an intramolecular reductive Michael-addition cascade employing Hantzsch ester as hydride source to a keto-bis-enone to provide enantio- and diastereoselective benzannulated diquinanes having three consecutive stereocenters, one of which is an all-carbon quaternary formyl stereocenter. Interestingly, on changing a tether connecting the ketone and an enone moiety from an aliphatic to an aromatic, a change in reactivity is observed. In this case, instead of the above-mentioned reductive aldol condensation, an asymmetric aldol reaction occurs, followed by an iminium/enamine isomerization and, finally diastereoselective Michael addition reaction occurs. As a result, a bis-benzannulated diquinane is obtained with vicinal congested quaternary chiral centers.     

Devices for Assisting Human Olfaction: Some Fundamental Experiments

Olfactory assist systems that allow the user to sense smells with amplified sensitivities are reported. We have developed two types of systems. The first system, an olfaction augmenter, detects the presence of a volatile organic compound in the air using a gas sensor, and presents an odor with an amplified intensity to the user using an odor generator. The second system, an olfactory concentrator, collects odor molecules in the air using an adsorbent, and presents the concentrated odor to the user. Results of our initial experiments on a prototype concentrator are reported.     

Macrolactonization via Ti(IV)-mediated epoxy-acid coupling: a total synthesis of (-)-dactylolide [and zampanolide

A total synthesis of dactylolide (1) is described. The key feature involves the Ti(IV)-mediated coupling of structurally complex "Sharpless epoxides" and carboxylic acids in either an intramolecular (macrolactonization) or an intermolecular mode. Other notable aspects include a proton-catalyzed, cis-selective construction of the 4-methylenetetrahydropyran ring; a selective oxidation of an allylic alcohol in the presence of a 1,2-diol by an oxoammonium ion; an efficient ring-closing metathesis reaction of an in situ (bis-TMS) protected alpha,omega-diene-vic-diol; and an aluminum-mediated aza-aldol reaction of a primary amide to 1 to construct the acyclic carbinolamide in zampanolide.     

Synthesis of 2,5-disubstituted octahydroquinolin-4-ones via anintramolecular hetero Diels-Alder reaction

A route for the preparation of 2,5-disubstituted octahydroquinolin-4-ones, synthetic precursors of the decahydroquinoline-type toxins, is presented. The key steps are an asymmetric epoxidation and an intramolecular hetero Diels-Alder reaction between an activated diene and an imine. The presence of an allylic stereogenic center induces some selectivity and thus only two cycloadducts are obtained in 70:30 ratio and good yield.     

Chiral sensing for amino acid derivative based on a [2]rotaxane composed of an asymmetric rotor and an asymmetric axle

A racemic [2]rotaxane, composed of an asymmetric rotor and an asymmetric axle, formed a diastereomer with an amino acid derivative, and showed an optical response for the chiral recognition.     

Protrusion and deformation of an elastic particle at an advancing front interface

The response of an elastic particle to an extensional field close to an advancing liquid–gas interface in a capillary was examined both from an experimental and theoretical viewpoint. Experimental evidence is given on both the protrusion and deformation of an elastic particle at an advancing front interface. To interpret our experimental results, we followed and extended Hoffman's approach to the case of deformable particles. A hybrid approach was followed where the height of the bump was calculated theoretically as an equilibrium between capillary and drag forces for a given deformation of the particle, whereas the latter was supplied by an independent experimental measurement. For an elastic particle, the height of the bump goes through a maximum and further on decay almost linearly when plotted against the dimensionless parameter introduced by Hoffman. The difference between the theoretical prediction and the experimental data is discussed in relation to the asymmetry of the bump profiles observed in the experiment that could be responsible for a larger contribution of capillary forces from those calculated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1362–1374, 2003     

An α-diaminoboryl carbanion assisted stereoselective single-pot preparation of α,β-disubstituted acrylonitriles

An α-diaminoboryl carbanion-mediated one-pot olefination directly converts an acetonitrile or the homologous nitrile into a series of α,β-disubstituted acrylonitriles in a stereoselective manner. The protocol involves the formation of an α-substituted α-diaminoboryl acetonitrile and subsequent olefination with an aldehyde. The use of an aryl or conjugated aldehyde preferentially leads to a (Z)-acrylonitrile, while an aliphatic aldehyde gave an (E)-isomer as a major product. Two complementary approaches, a linear method and a divergent method, are developed.     

Mechanism of the α,α-diarylprolinol trimethylsilyl ether-catalyzed enantioselective C-C, C-N, C-F, C-S, and C-Br bond forming reactions

Theoretical calculations were employed to investigate the enantioselectivity of the α,α-diarylprolinol trimethylsilyl ether-catalyzed α-functionalization of aldehydes with various different electrophiles, via an enol intermediate. The reactions investigated were (i) Michael-aldol condensation, (ii) Michael addition, (iii) Mannich reaction, (iv) α-amination of an aldehyde, (v) α-fluorination of an aldehyde, (vi) α-sulfenylation of an aldehyde, and (vii) α-bromination of an aldehyde. In all seven cases, our proposed enol mechanism is able to account for the experimentally observed enantioselectivity of the products. Our calculations strongly suggest that these catalyzed reactions proceed via an enol intermediate and not via an enamine intermediate.     

A facile synthesis of phytosphingosine from diisopropylidene-D-mannofuranose

In the present study, an efficient method with a high overall yield for preparing phytosphingosine and an analogue was developed. Starting with commercially available 2,3;5,6-di-O-isopropylidene-d-mannofuranose, a variety of lipid moieties were incorporated to obtain phytosphingosine and an analogue. Through an eight-step manipulation, phytosphingosine was obtained with an overall yield of 57%.     

A Synthesis of the Tricyclic Core Structure of FR901483 Featuring an Ugi Four-Component Coupling and a Remarkably Selective Elimination Reaction

Three key reactions, an efficient Ugi four-component coupling, a regiospecific, base-mediated elimination reaction, and an intramolecular nitrone/alkene [3+2] cycloaddition, were used to achieve an effective synthesis of the tricyclic molecular framework of the immunosuppressant FR901483. The outcome of a control experiment supports the idea that an internal deprotonation by an alkoxide ion is the origin of the site selectivity observed in the base-induced elimination of hydroxy mesylate 17.     

Nickeladihydrofuran. Key intermediate for nickel-catalyzed reaction of alkyne and aldehyde

The formation of a nickeladihydrofuran by oxidative cyclization of an alkyne and an aldehyde with nickel(0) has been demonstrated; the transformation of the nickeladihydrofuran into an enone by decomposition, a lactone by carbonylation and an allylic alcohol by treatment with ZnMe(2) suggests that nickeladihydrofuran is an important key intermediate in a variety of catalytic reactions.     

Cationic carbohydroxylation of alkenes and alkynes using the cation pool method

The reactions of an N-acyliminium ion pool with alkenes and alkynes gave gamma-amino alcohols and beta-amino carbonyl compounds, respectively, after treatment with H(2)O/Et(3)N. The present reaction serves as an efficient method for cationic carbohydroxylation of alkenes and alkynes. When vinyltrimethylsilane was used as an alkene, the reaction was highly diastereoselective and served as an access to an enantiomerically pure alpha-silyl-gamma-amino alcohol. [reaction: see text]     

Sur un effet de solvant inhabituel sur une reaction de menschutkin intramoleculaire

The influence of solvation on the reaction rate of an intramolecular quaternisation, may be different from the rate observed for an intermolecular reaction of the same type. In the intermolecular reaction, if the polarity of an aprotic solvent increases, the partially charged transition state is more stable than the initial state. In the contrary, for an intramolecular reaction the conformation of the different states (initial and transition) plays an important role. So that, if the polarity of an aprotic solvent increases, one conformation of the uncharged initial state may be, by its geometry more stable than the partially charged transition state. An interpretation based on the conformation, explains why in one case and in comparison with CH₃CN, methanol accelerates the intramolecular reaction whereas the contrary is always observed for an intermolecular one.     

Electrocatalytic Multicomponent Reaction for Synthesis of Nanoparticles of Spirooxindole Derivatives from Isatins,Malononitrile, and Dimedone

An electrocatalytic multicomponent synthesis of nanoparticles of spirooxindole is described, using an electrogenerated base of the anion of propanol in a one‐pot, three component condensations of an isatins, dimedone, and malononitrile in an undivided cell in the presence of sodium bromide as an electrolyte at 50°C.     

Pd‐Catalyzed Csp2H Functionalization of Heteroarenes via Isocyanide Insertion: Concise Synthesis of Di‐(Hetero)Aryl Ketones and Di‐(Hetero)Aryl Alkylamines

We report herein an efficient Pd‐catalyzed direct C?H bond functionalization of heteroarenes via an isocyanide insertion strategy for the synthesis of di‐(hetero)aryl ketones and di‐(hetero)aryl alkylamines. The methodology involves a three component reaction between an azole, a haloarene and an isocyanide resulting in the formation of an imine, which in turn is either hydrolyzed or reduced to get the desired product.     

One-pot preparation of azobenzenes from nitrobenzenes by the combination of an indium-catalyzed reductive coupling and a subsequent oxidation

We demonstrated how a reduction step with a reducing system comprised of In(OTf)₃ and Et₃SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group.     

Synthesis of triazolyl-alkylphosphonate starting from ω-azidoalkylphosphonates or ω-alkynylphosphonates

1,2,3-Triazolyl-alkylphosphonates are synthesised according to a Huisgen 1,3-dipolar cycloaddition catalysed by copper salts. The cycloaddition of either an alkynylphosphonate with an azidoalkane or an azido-phosphonate with an alkyne is achieved in high yield and regiospecifically. As an illustration of the functionalisation of aromatic ligands by using the catalytic version of the Huisgen reaction, the coupling of 3-ethynyl-1,10-phenanthroline with azidoalkylphosphonate is reported.     

Curtius rearrangement of aromatic carboxylic acids to access protected anilines and aromatic ureas

The reaction of a chloroformate or di-tert-butyl dicarbonate and sodium azide with an aromatic carboxylic acid produces the corresponding acyl azide, presumably through the formation of an azidoformate. The acyl azide undergoes a Curtius rearrangement to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea. The reaction conditions are compatible with a variety of functional groups and allow the synthesis of a number of aniline derivatives containing alkyl, halide, nitro, ketone, ether, and thioether substituents. [reaction: see text]     

Electronic influences in the molecules of group IV organometallic compounds

On the basis of an analysis of the characteristic properties in the vibrational and NMR spectra of some hydrides and alkyl and vinyl derivatives of C, Si, Ge, and Sn(M), an explanation is given for an effect which appears in the organic compounds of Group IV B elements as due to an increase in the electron-acceptor properties of the heteroatoms.