A New Chemical Method to Desulfenylate Indol-3-yl Sulfides

Abstract

Desulfenylation of indol-3-yl sulfides liberates the most reactive position of the ring for further transformations. The usual procedure, utilizing Raney Nickel (P. G. Gassman, et. al., J. Am. Chem. SOC. 1974,96, 5495) offers a limited scope due to incompatibility of a number of functional groups towards the reducing agent. Based on our recent mechanistic studies of the acid-catalysed rearrangement of indol-3-yl sulfides to indol-2-yl sulfides (P. Hamel, et. al., Chem. Commun. 1989, 63; J. Org. Chem. 1992, 57, 2694), we have developed a novel, non-reductive desulfenylation method which permits easy access to 3-unsubstituted indoles bearing a wide array of substituents. Thus, 3-indolyl sulfides, readily obtained from appropriate phenylhydrazines (via Fischer indolization) or anilines (Gassman method, vide infra) are smoothly desulfenylated in good yields in trifluoroacetic acid in the presence of an appropriate nucleophilic trapping agent. Thiols proved to be very effective trapping agents and thiosalicylic acid (TSA) is a thiol of choice, being non-volatile and easily separable from reaction products.     

TELOMERISATION PAR CATALYSE REDOX IX ADDITION DE TELOGENES PHOSPHORES SUR DES COMPOSES POSSEDANT DEUX DOUBLES LIAISONS NON CONJUGUEES

Abstract

The synthesis of telechelic oligomers with phosphorated end groups was realized by redox catalysis telomerization reaction by addition of phosphorated telogens containing a trichloromethyl group on monomers with two non-conjugated double bonds.

Nous effectuons la synthèse d'oligoméres téléchéliques à extrémités phosphorées en additionnant au moyen de la réaction de télomerisation par catalyse Redox des télogènes phosphorés renfernant le groupement trichlorométhyle, sur des monomères à deux doubles liaisons non conjuguées.     

Simple Method for the Preparation of 1,3-Dithiol-2-one and 1,3-Dithiol-2-thione

Abstract

The reaction of diisopropyl xanthogen and thio-diisopropyl xanthogen disulfide with alkynes furnished 1,3-dithiol-2-one and 1,3-dithiol-2-thione.     

Gas‐phase interactions of organotin compounds with glycine

Gas‐phase interactions of organotins with glycine have been studied by combining mass spectrometry experiments and quantum calculations. Positive‐ion electrospray spectra show that the interaction of di‐ and tri‐organotins with glycine results in the formation of [(R)₂Sn(Gly)‐H]⁺and [(R)₃Sn(Gly)]⁺ ions, respectively. Di‐organotin complexes appear much more reactive than those involving tri‐organotins. (MS/MS) spectra of the [(R)₃Sn(Gly)]⁺ ions are indeed simple and only show elimination of intact glycine, generating the [(R)₃Sn]⁺ carbocation. On the other hand, MS/MS spectra of [(R)₂Sn(Gly)‐H]⁺complexes are characterized by numerous fragmentation processes. Six of them, associated with elimination of H₂O, CO, H₂O + CO and formation of [(R)₂SnOH]⁺ (?57 u),[(R)₂SnNH₂]⁺( ?58 u) and [(R)₂SnH]⁺ (?73 u), are systematically observed. Use of labeled glycines notably concludes that the hydrogen atoms eliminated in water and H₂O + CO are labile hydrogens. A similar conclusion can be made for hydrogens of [(R₂)SnOH]⁺and [(R₂)SnNH₂]⁺ions. Interestingly, formation [(R)₂SnH]⁺ ions is characterized by a migration of one the α hydrogen of glycine onto the metallic center. Finally, several dissociation routes are observed and are characteristic of a given organic substituent. Calculations indicated that the interaction between organotins and glycine is mostly electrostatic. For [(R)₂Sn(Gly)‐H]⁺complexes, a preferable bidentate interaction of the type η²‐O,NH2 is observed, similar to that encountered for other metal ions. [(R)₃Sn]⁺ ions strongly stabilize the zwitterionic form of glycine, which is practically degenerate with respect to neutral glycine. In addition, the interconversion between both forms is almost barrierless. Suitable mechanisms are proposed in order to account for the most relevant fragmentation processes. Copyright © 2013 John Wiley & Sons, Ltd.     

Ligand Functionalization and Its Effect on CO2 Adsorption in Microporous Metal–Organic Frameworks

We report two new 3D structures, [Zn₃(bpdc)₃(2,2′‐dmbpy)] (DMF)_x(H₂O)_y ( 1 ) and [Zn₃(bpdc)₃(3,3′‐dmbpy)]?(DMF)₄(H₂O)_0.5 ( 2 ), by methyl functionalization of the pillar ligand in [Zn₃(bpdc)₃(bpy)] (DMF)₄?(H₂O) ( 3 ) (bpdc=biphenyl‐4,4′‐dicarboxylic acid; z,z′‐dmbpy=z,z′‐dimethyl‐4,4′‐bipyridine; bpy=4,4′‐bipyridine). Single‐crystal X‐ray diffraction analysis indicates that 2 is isostructural to 3 , and the power X‐ray diffraction (PXRD) study shows a very similar framework of 1 to 2 and 3 . Both 1 and 2 are 3D porous structures made of Zn₃(COO)₆ secondary building units (SBUs) and 2,2′‐ or 3,3′‐dmbpy as pillar ligand. Thermogravimetric analysis (TGA) and PXRD studies reveal high thermal and water stability for both compounds. Gas‐adsorption studies show that the reduction of surface area and pore volume by introducing a methyl group to the bpy ligand leads to a decrease in H₂ uptake for both compounds. However, CO₂ adsorption experiments with 1′ (guest‐free 1 ) indicate significant enhancement in CO₂ uptake, whereas for 2′ (guest‐free 2 ) the adsorbed amount is decreased. These results suggest that there are two opposing and competitive effects brought on by methyl functionalization: the enhancement due to increased isosteric heats of CO₂ adsorption (Q_st), and the detraction due to the reduction of surface area and pore volume. For 1′ , the enhancement effect dominates, which leads to a significantly higher uptake of CO₂ than its parent compound 3′ (guest‐free 3 ). For 2′ , the detraction effect predominates, thereby resulting in reduced CO₂ uptake relative to its parent structure 3′ . IR and Raman spectroscopic studies also present evidence for strong interaction between CO₂ and methyl‐functionalized π moieties. Furthermore, all compounds exhibit high separation capability for CO₂ over other small gases including CH₄, CO, N₂, and O₂.     

Synthesis of New Iminocoumarins Bearing Parabanic Moieties

The synthesis of novel substituted 3-p-nitro-phenyliminocoumarins and corresponding N-ureaiminocoumarins is described. The condensation of these materials with oxalyl chloride leads to the corresponding N-parabanic iminocoumarins, which have not previously been described, in moderate or good yields and high selectivity. The structures were characterized by Fourier transform infrared, ¹H and ¹³C NMR, and elemental analysis.

A study of morphological,thermal, rheological and barrier properties of Poly(3-hydroxybutyrate-Co-3-Hydroxyvalerate)/polylactide blends prepared by melt mixing

The paper aims to study blend properties of biodegradable polymers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) prepared by melt mixing. Blend compositions based on PHBV/PLA were investigated according to the following weight ratios, i.e. 100/0, 75/25, 50/50, 25/75 and 0/100 wt%. The study showed through scanning electron microscopy (SEM) that blends of PHBV/PLA are not miscible. This is consistent with differential scanning calorimetry (DSC) data which indicate the presence of two distinct glass transition temperatures (T_g) and melting temperatures (T_m), attributed to the neat polymers, over all the range of blend compositions. Water and oxygen barrier properties of PHBV/PLA blends are significantly improved with increasing the PHBV content in the blend. Further, morphological analyzes indicated that increasing the PHBV content in the polymer blends results in increasing the PLA crystallinity due to the finely dispersed PHBV crystals acting as a filler and a nucleating agent for PLA. On the other hand, the addition of PLA to the blend results in a very impressive increase in the complex viscosity of PHBV. Moreover, the rheological data showed that, excluding the specific behavior of the neat polymers at low frequencies, i.e. less than 0.1 Hz, the complex viscosity of PHBV/PLA blends fits the mixing law well.     

Synthesis of Artificial Glycoconjugate Polymers Carrying 6-O-Phosphocholine α-D-Glucopyranoside,Biologically Active Segment of Main Cell Membrane Glycolipids of Mycoplasma Fermentas

ABSTRACT

The conformation of two mannose-based amidines, the N-benzylmannoamidine and a pseudo (1→6) dimannoside, has been evaluated using semi-empirical AMI calculations and ¹H NMR studies. The most stable conformations of the mannoamidine ring correspond to the half-chair forms ³H₄ and ⁴H₃. The conformations (Z) or (E) about the exocyclic C-N bond depend on the substituents and it was shown that, in solution, the N-benzylmannoamidine was (E)-configured whilst the pseudo (1→6) dimannoside was (Z)-configured. Using the grid-search approach, the potential energy maps of both mannoamidines were calculated as a function of the torsion angles which define the orientation of the amidine substituent. Three stable conformers were identified for the N-benzylmannoamidine and seven for the pseudo (1→6) dimannoside. Inter-glycosidic NOE have provided evidence for a preferred conformation of the pseudo (1→6) dimannoside in solution. The transition state structure of the α-phenylmannose hydrolysis was optimized using the AMI method and compared to the N-benzylmannoamidine. The developing oxocarbenium ion is well matched by the mannoamidine ring but the orientation of the phenyl group in the inhibitor differs significantly from the position of the leaving group in the transition state. The use of sugar type amidines as haptens to obtain catalytic antibodies is then discussed.