SYNTHESIS OF N-SUBSTITUTED PYRROLO[3,4-b]INDOLES FROM 2,3-DIMETHYLINDOLE

ABSTRACT

Pyrrolo[3,4-b]indoles 8 are conveniently synthesized from 2,3-dimethylindole (4) in four steps, the last of which is DDQ oxidation of dihydropyrrolo[3,4-b]indoles 7 (85–98% yield).     

Concise Synthesis of 6-Cyanobenzo[b]furan,a Useful Building Block

A new three-step synthesis of 6-cyanobenzo[b]furan (6) was developed, starting from commercially available 6-hydroxybenzo[b]furan-3-one (18). Key steps in this process were the first step, which was the reductive dehydration of 18 to produce 6-hydroxybenzo[b]furan (19), and the last step, which converted the aryl triflate 20 to the aryl cyanide 6 in a palladium-catalyzed cross-coupling protocol. Overall yield for this new synthesis was 49%.     

Synthesis of Polyphosphazenes from P-Trichloro-N-Dichlorophosphoryl Monophosphazene Cl3P=N-P(O)Cl2

Abstract

The polycondensation of P-Trichloro-N-dichlorophosphoryl monophospha-zene Cl₃P = N-P(0)Cl₂ has been studied. This last develops according to the reaction     

Ringschlußreaktionen von 2-Acyl-1-chlor-enaminen mit thioamidfunktionellen Verbindungen: Wahlweiser Zugang in die 1,3-Thiazin- und 1,3-Oxazin-Reihe

2-Acyl-1-chloro-enamines2 react with thioureas to 2,6-diamino-1,3-thiazinium salts3, following the usual transformation mode of 1-heterosubstituted acylvinylchloridesA. On the other hand the reaction of2 with thiobenzamide preferably leads to 4-amino-1,3-oxazinium salts7. The last course is discussed in terms of imidoyl-migration in the primary productE formingF, which finally undergoes ring condensation. This assumption corresponds in the best way with all experimental findings, moreover with special model reactions (e.g.2 13).

Herrn Prof. Dr.Klaus Hafner zum 60. Geburtstag gewidmet.     

Structure of Dibenzocrown Ethers and their H-Bonded Adducts.1. [1.5]Dibenzo-18-Crown-6 and Biphenyl-20-Crown-6: Complexes with Amidosulfuric Acid

The interaction of the amidosulfuric acid NH ₃ SO ₃ with 15 distal and proximal dibenzocrown ethers, including diphenyloxide, diphenylsulfide and biphenyl ones leads to the stable (1:1) complexes only in the case of [2.4]- and [1.5]dibenzo-18-crown-6 and biphenyl-20-crown-6. According to the data of the X-ray analysis, in the two last adducts the amidosulfuric acid coordinates to hexadentate crown ethers in a zwitterion form through a near-ideal ‘tripod’ arrangement to alternate crown oxygen atoms. The conformations of crown molecules are different in complexes and in initial macrocyclic ligands.This revised version was published online in July 2005 with a corrected issue number.     

A Convenient Synthesis of N-Functionalized Perfluoroalkanesulfonamides

This article describes the synthesis of new N-functionalized perfluoroalkanesulfonamides (5) with two sulfonamides functionalities. Perfluoroalkanesulfonyl fluoride underwent a reaction with 2-chloroethylamine hydrochloride or 3-bromopropylamine hydrobromide to give N-(2-chloroethyl or 3-bromopropyl) perfluoroalkanesulfonamides (1). Reaction of (1) with potassium thiocyanate gave N-(2-thiocyanatoethyl or 3-thiocyanatopropyl) perfluoroalkanesulfonamides (3). The sulfonyl chloride derivatives (4) were prepared by reaction of 3 with sulfuryl chloride. In the last step, 4 reacted with ammonia to give the bis sulfonamides derivatives (5). The structures of all new compounds prepared were determined by ¹H, ¹⁹F, and ¹³C NMR spectroscopies and by HR-MS.     

Heterocycles With a Benzothiadiazepine Moiety. IV. Synthesis of Novel Tetracyclic Rings by Intramolecular Cyclization of 10-Bromoacetyl-10,11-dihydro-11-ethoxycarbonyl-pyrrolo[1,2-b] [1,2,5] Benzothiadiazepine 5,5-Dioxide and Its Derivatives

Two novel tetracyclic derivatives, namely 5 and 8, have been synthesized by intramolecular cyclization of the 10-bromoacetyl-10,11-dihydro-11-ethoxycarbonylpyrrolo[1,2-b] [1,2,5]benzothiadiazepine 5,5-dioxide (3) and, respectively, the bis-methylamide of 11-carboxy-10,11-dihydropyrrolo[1,2-b] [1,2,5]benzothiadiazepine-11-acetic acid 5,5-dioxide (4). The last compound formed when treating with an excess of methylamine either the lactam 5 or the diethyl ester of 11-carboxy-10,11-dihydropyrrolo[1,2-b] [1,2,5]benzothiadiazepine-11-acetic acid 5,5-dioxide (7). An unambiguous synthesis of the diester 7 was achieved to confirm the chemical structure of derivatives 4 and 5.     

FROM 1,3-DIPHOSPHETANE-2,4-DIYLS TO CYCLIC ANIONS AND CATIONS

The interest in diradicals has grown by the increasing number of stable diradicals which have been synthesized during the last few years. The diphosphacyclobutane-diyles have a diradicaloid molecular structure and they were the first diradicals to be prepared in the gramme scale. The combination of stability and high yield synthesis creates the opportunity both to change the substitution pattern or to prepare different valence isomers. Current experimental and computational studies reveal that electron transfer reactions of maintain the cyclic system. In the contribution, the oxidation reaction of 1 to the radical cation 2 and the cyclic diphosphaallyl cation 3 will be reported. Additionally, the remarkable mechanism of the reaction of 1 at first to the radical anion 4 but particularly to the diphosphacyclobutadiene dianion 5 under reductive conditions will be presented in detail.     

A Comparative Study of the Cyclic Chlorophosphites with C2-Symmetrical Organic Fragments as the Reagents for Enantiomeric Composition Control of the Chiral Alcholos

Abstract

The ³¹P NMR method is intensively used for enantiomeric composition control during the last years [1]. Among all other derivatizing agents the C₂-symmetrical ones have some advantages.     

Improved Synthetic Approach to Tenatoprazole

An improved synthetic approach to tenatoprazole 1 is described. It started from 2,3,5‐trimethyl‐4‐nitropyridine‐N‐oxide 2 with acetic anhydride via rearrangement and hydrolysis to give 3, Chlorination with SOCl₂ yielded 2‐chloromethyl‐3,5‐dimethyl‐4‐nitropyridine hydrochloride 4, then 4 condensed with 2‐mercapto‐5‐methoxy imidazole [4,5‐b]pyridine 5 to give 5‐methoxy‐2‐[(4‐nitro‐3,5‐dimethyl‐2‐pyridinyl)methylthio]imidazole[4,5‐b]pyridine 6. At last the title compound 1 was produced by two methods: 6 was oxidized with MCPBA and then methoxylated with CH₃ONa to give 1 and 6 was first methoxylated with CH₃ONa and then oxidized with MCPBA to give 1. The overall yield is around 26% for both five‐step syntheses.     

A Comparative Study of the Cyclic Chlorophosphites with C2-Symmetrical Organic Fragments as the Reagents for Enantiomeric Composition Control of the Chiral Alcohols

Abstract

The ³¹P NMR method is intensively used for enantiomeric composition control during the last years [I]. Among all other derivatizing agents the C2-symmetrical ones have some advantages.     

Reactivity of Conjugate Bases of Hydridophosphoranes. Synthesis of New Phosphoranes Involving P-P Bonds

Abstract

Hydridophosphoranes 1, 2 react, in presence of triethylamine, with phenyldichlorophosphine, diphenylchlorophosphine and the chlorophosphorane 3 giving unusual phosphoranes bearing P-P bonds. These last have been isolated and their structure has been determined by NMR spectroscopy.     

Complete resolution of the reaction Rates of flavylium Networks. The role played by 2-phenyl-2H-chromen-4-ol and the hydroxyl attack to the quinoidal Base

Complete analytical resolution of the network of chemical reactions involving the flavylium compounds was achieved by means of the Laplace transform, general partial fraction theorem and Vieta’s formulae. The kinetic model includes basic and acid catalysis of the hydration and tautomerization reactions. The formation of phenyl-2H-chromen-4-ol (B ₄ ) and the role it plays in the kinetics in the case of compounds lacking of the hydroxyl substituents was also accounted for. In all cases four kinetic steps could be individualized and the pH dependent mole fraction distribution of the several species monitored as a function of time, the last one leading to the equilibrium. It is worth of note the role of B ₄ in the network, which like the quinoidal base is a kinetic product that retards the formation of Ct. The evolution of B ₄ is also dependent on the existence or not of the cis-trans isomerisation barrier. Application of the model to the data of flavylium networks previously reported in literature, predicts with great accuracy the respective behavior.     

Mesogenic quinazolone derivatives: synthesis and characterisation

Two new mesogenic homologous series of quinazolone derivatives have been synthesised by condensation of 4-n-alkoxybenzoyloxy benzaldehyde (for series I) / 4-n-alkoxy-3-methoxybenzoyloxy benzaldehyde (for series II) with 3-amino-2-methyl quinazolone in alcohol. The synthesised compounds are characterised by a combination of elemental analysis and standard spectroscopic methods. In series I, all the synthesised members exhibit the nematic mesophase. An enantiotropic smectic A phase is observed from the n-decyloxy derivative onward to the last homologue synthesised. Methoxy to n-propyloxy derivatives of series II are non-mesogenic, whereas the rest of the members exhibit a monotropic nematic mesophase. The mesomorphic properties of the present series I and II are compared with each other and with the other structurally related mesogenic homologous series to evaluate the effect of lateral methoxy substituent and quinazolone moiety on mesomorphism.     

Optimization Methods For Hplc

Abstract

As almost every researcher in the field might be able to have a literature search done in the Chemical Abstracts on the keywords “HPLC” and “Optimization”, no bare summing up of all papers that have been published in the last few years on this particular subject will be found in this review.     

Synthetic approaches toward piperidine related structures: A review

Abstract

The current review covers explosive development of various synthetic approaches for piperidine scaffold and its analogues in the last few decades. The piperidine ring system is a key motif in many natural alkaloids and synthetic organic compounds. Further, piperidine moiety has gained significant consideration in drug discovery due to its wide range of therapeutic applications.     

Reverse Osmosis Membranes for Seawater Desalination State-of-the-Art

Abstract

The field of membrane technology has developed very rapidly during the last three decades. In this study, the major technical and commercial developments that took place in the field of reverse osmosis membranes as applied to seawater desalination are investigated. A brief historical review for each membrane type is also presented.     

Photochemical behaviour of Schiff base liquid crystals based on isoxazole and isoxazoline ring. A kinetic approach

ABSTRACT

The kinetic study on the hydrolysis of Schiff bases (SBs) 1a-c and 2a-c induced by UV-vis was undertaken as a complementary study of the stability in solution and in bulk of the SBs. Solutions in chloroform were exposed to UV-vis and acquisition data occurred for 1a-c and for 2a-c in 21°C, 30 °C, 35°C and 40°C. Kinetic profile for 1a-c and 2a-c displayed the similar photochemical behaviour in that four temperature values. At 21°C, two kinetic regimes were observed where the decomposition of SBs is faster at the initial stage, with no linear plot of absorbance vs time, and after the kinetic profile obeyed a linear behaviour. A mathematical treatment of the experimental data was applied, which allowed associating the initial stage data with a second-order reaction, and the final stage of the hydrolysis with a first-order reaction. The mechanism of photochemical hydrolysis of SBs 1a and 2a was addressed. It was composed of three parts, the excitation, then the isomerisation and activation processes of tetrahedral intermediate and, the last process, a collapse of the intermediate to the yielded products of the hydrolysis aldehydes and amines which were detected by their UV-vis spectrum.     

SYNTHESIS OF CHIRAL SULFOXIDES BY ASYMMETRIC OXIDATION

Abstract

The main chemical or enzymatic methods of asymmetric oxidation of sulfides are reviewed. A new approach to chiral sulfoxides is described, which uses tertiobutyl hydroperoxide in presence of a chiral titanium complex. The results obtained during the last two years are summarized. The best enantiomeric excess amounts to 95% in the case of formation of cyclopropyl phenyl sulfoxide.     

Phosphorotropic Tautomerism in Amidine Systems

Abstract

During the last years considerable progress was made in the study of phosphorotropic tautomeric transformations, which involves quick reversible migrations of phosphorus groups between nucleophilic centers of molecule. Phosphorotropic systems may serve a s simple and clear models for study of the mechanism of substitution reactions at the phosphorus atom.