BF3 Et2O Research Articles

Cyclic Azobenzene-BODIPY Hybrids.

Cyclic azobenzene-BODIPY hybrids were synthesized via cyclization by 1) acid-catalysed condensation of azobenzene-bridged dipyrroles with 3,5-di-tert-butylbenzaldehyde, 2) oxidation with DDQ, and 3) metalation with BF3 ⋅ Et2 O. The structures of many cyclic hybrids have been confirmed by single crystal X-ray analysis. The absorption spectra of the hybrids reveal the effective cyclic conjugation. The ultrafast measurements reveal that the photoexcited decays of these cyclic hybrids depend upon the ring size and connectivity.

Mono- and bis-phenoxy-substituted 3-(quinolin-2-ylmethylene)isoindolin-1-ones and their boron complexes. Synthesis, photophysical properties and conductivity of thin films

Heating 4-phenoxyphthalimide or 4,5-diphenoxyphthalimide with quinaldine in the presence of zinc oxide leads to the formation of (E,Z)-5(6)-phenoxy-3-(quinolin-2-ylmethylene)isoindolin-1-one and (E,Z)-5,6-diphenoxy-3-(quinolin-2-ylmethylene)isoindolin-1-one. By reacting them with BF3‧Et2O in the presence of Et3N in toluene, unsymmetrical analogs of BODIPY were synthesized, namely (Z)-2-(difluoroboryl)-5(6)-phenoxy-3-(quinolin-2-ylmethylene)isoindolin-1-one and (Z)-2-difluoroboryl-5,6-diphenoxy-3-(quinolin-2-ylmethylene)isoindolin-1-one, respectively. By structure of the synthesized compounds was confirmed by the data of elemental analysis, mass spectrometry, vibrational and NMR spectroscopy. The ligands have low fluorescence quantum yields (up to 0.14 relative to the standard) and significant Stokes shifts (up to 140 nm). In contrast, the complexes demonstrate high quantum yields (up to 0.44) and small Stokes shifts (7–8 nm). The fluorescence lifetimes of the complexes are close to 3 ns. To support the experimental data, DFT and TD-DFT calculations were carried out. Thin films of the complexes have a specific conductivity of 10−8 ÷ 10−9 S × cm−1 and the monophenoxy-substituted complex exhibits high photosensitivity.

Metal-Free Synthesis of 2-Substituted Quinazolines via Green Oxidation of o-Aminobenzylamines: Practical Construction of N-Containing Heterocycles Based on a Salicylic Acid-Catalyzed Oxidation System.

Conventional quinazoline synthesis methods involve a highly multistep reaction, and often require excess amounts of substrate to control the product selectivity, leading to significant resource wastage. Hence, in this study, from the viewpoint of green chemistry, we developed a novel metal-free synthetic method for 2-substituted quinazoline derivatives by the 4,6-dihydroxysalicylic acid-catalyzed oxidative condensation of o-aminobenzylamines and benzylamines using atmospheric oxygen. In this system, the use of a catalytic amount of BF3‧Et2O (10 mol%) as a Lewis acid successfully led to the efficient oxidative condensation and intramolecular cyclization of these amines, followed by aromatization to afford the corresponding 2-arylquinazolines in up to 81% yield with excellent atom economy and environmental factor. Furthermore, to expand this green oxidation method to gram-scale synthesis, we investigated the development of an oxidation process using salicylic acid itself as an organocatalyst, and established a method for the practical green synthesis of a series of nitrogen-containing heterocycles. We expect that the findings will contribute to the development of practical synthesis methods for pharmaceutical manufacturing and industrial applications, along with further advancements in green chemistry.

Reactions of (+)-Camphene with Dithiols

Electrophilic addition of thiols to camphene is known characteristically to follow various pathways and to produce both adducts that retain the starting camphene structure against Markovnikov’s rule or according to it and isomerization products that most frequently have the bornane structure [1–6]. We studied previously the BF3 Et2O-catalyzed addition of a series of thiols to (+)-camphene. Terpene sulfides with the camphene or bornane structure were formed according to Markovnikov’s rule for aromatic and heteroaromatic thiols whereas the reactions with other thiols went against the rule and retained the starting structure [7]. In continuation of research on the electrophilic addition of S-containing reagents to (+)-camphene (1), we studied its reaction with bifunctional thiols such as 1,2-ethanedithiol and bis(2-mercaptoethyl)sulfide under various conditions by varying the catalyst (BF3 Et2O or ZnCl2) and substrate:reagent ratio (Scheme 1).

Improved synthesis of mercapto C-nucleoside possessing p-phenyl thiol as base using a lithiated coupling reaction

We have developed a new route for synthesizing mercapto C-nucleoside possessing a phenyl thiol group, using organometallic reagents. Duplexes incorporating redox-active nucleobase analogues display a high melting temperature under oxidation condition. Originally, we had anticipated the production of mercapto C-nucleoside using a Friedel–Crafts coupling reaction via bis(toluoyl) protected ribose and tert-butyl phenyl sulfide in the presence of Lewis acid. However, an undesired coupling compound was formed by cleavage of the S-tert-butyl group of S-tert-butyl phenyl sulfide by Lewis acids (BF3 Et2O, SnCl4). The highly stereoselective synthesis of mercapto C-nucleoside was, however, achieved by the addition of p-(tert-butyl)thiophenyllithium to a disiloxane-protected 2-deoxyribonolactone. This route showed moderately good yield at all steps. The tert-butyl moiety coupled to the sulfur atom at the phenyl group was converted to a 2-nitrophenylsulfenyl (Nps) group, and the Nps group was easily cleaved by ethanethiol to afford the desired compound and its disulfide dimer.

Synthesis and Biological Evaluation of Some Tetrahydroquinoline Compounds Derived from 4- Aminobenzenesulfonamid

In the present study, five compounds of 1,2,3,4-tetrahydroquinolines derivatives of 4- Aminobenzenesulfonamid were prepared through Imines – Diels – Alder reaction by reacting Schiff bases with cinnamic acid and Bf3 Et2O in ethanol. The Schiff bases were synthesized by treating various aromatic aldehydes with 4-Aminobenzenesulfonamid. The structures of the synthesized compounds were determined on the basis of their FTIR, UV and C.H.N spectral data. The in vitro antibacterial and antifungal activities of the compounds were evaluated by paper disc diffusion method. The synthesized compounds were determined by using the Minimum Inhibitory Concentration (MIC).Significant antimicrobial activities were observed for some compounds of the series

Benzylation of arenes with benzyl ethers promoted by the in situ prepared superacid BF3–H2O

An efficient and environmentally friendly benzylation of arenes with benzyl ethers as benzyl donors using BF3–Et2O to generate in situ the superacid BF3–H2O as an efficient promotor has been described. A wide variety of functional groups have been investigated and found to be compatible to give the desired diarylmethanes in yields of up to 99%. The crucial role of the moisture content in this transformation has been demonstrated by detailed investigations.

Ionic liquid-promoted stereoselective [3 + 2] cycloaddition of 1-hetaryl-2-nitroethenes to azomethine imines generated in situ

Ionic liquids facilitate regio- and stereoselective [3 + 2] cycloaddition of 1-hetaryl-2-nitroethenes to azomethine imines generated catalytically from 6-Ar-1,5-diazabicyclo[3.1.0]hexanes in the presence of BF3 Et2O. The similar reaction is possible in MeCN only for azomethine imine with Ar = 2,4-(MeO)2C6H3 to give a mixture of two diastereomers.

Hypervalent phenyl-λ3-iodane-mediated para-selective aromatic fluorination of 3-phenylpropyl ethers

Exposure of 3-phenylpropyl ethers to an activated iodosylbenzene monomer·18-crown-6 complex [PhI(OH)BF(4)·18C6] in the presence of BF(3)-Et(2)O and water results in the para-selective monofluorination of benzene ring via neighboring alkoxy group participation and directly affords 3-(4-fluorophenyl)propyl ethers regioselectively in good yields.

One-pot synthesis of the naturally occurring dimeric carbazole alkaloid murranimbine and its analogue

Murranimbine, a naturally occurring dimeric carbazole alkaloid, isolated from the root bark of Murraya euchrestfolia was synthesized in one step by the application of Lewis acid (BF3–Et2O) on its monomer girinimbine. A new dimer of koenidine was also synthesized following the same procedure. Structures of these dimeric carbazole alkaloids were determined by detailed spectral analysis.

Synthesis of Substituted Imidazolines via [3 + 2]‐Cycloaddition of Aziridines with Nitriles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of substituted imidazolines via [3+2]-cycloaddition of aziridines with nitriles

An efficient synthesis of 2,4-disubstituted 1H-imidazolines from aziridines and nitriles in the presence of BF3–Et2O or triethyloxonium tetrafluoroborate has been described. The reaction proceeds via a [3+2]-cycloaddition reaction. Most of the nitriles successfully underwent cycloaddition reactions with aziridines even at room temperature in a very short time.

The Efficient Synthesis of New Sydnones Containing Fused Ring.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A simple synthesis of C-10 substituted deoxoartemisinin and 9- epi-deoxoartemisinin with various organozinc reagents

A direct substitution reaction of 10α- or 10β-benzenesulfonyl dihydroartemisinin, prepared from dihydroartemisinin with thiophenol in the presence of BF 3Et 2O and consecutive oxidation with H 2O 2/urea complex, with organozinc reagents derived from allyl, benzyl, phenyl, vinyl and n-butyl Grignard reagents stereoselectively produced C-10 substituted deoxoartemisinins in good to moderate yields. The same reaction of 10β-benzenesulfonyl-9- epi-dihydroartemisinin gave corresponding 9- epi-deoxoartemisinin derivatives.

THE EFFICIENT SYNTHESIS OF NEW SYDNONES CONTAINING FUSED RING

ABSTRACT Sydnones 2a–f were prepared by the reaction of the corresponding sydnones 1a–f with acetone in the presence of concentrate sulfuric acid or BF3–Et2O.

Investigation of porphyrin-forming reactions. Part 2. Examination of the reaction course in two-step, one-flask syntheses of meso-substituted porphyrins †

The reaction course leading to meso-substituted porphyrins was examined for reversibility (formation of oligomers, formation of α- and β-pyrrole linkages), inactivation of the acid catalyst, homogeneity of the reaction medium, and the pathway of oligomer formation. The methodology employed enabled characterization of the oligomer composition (LD-MS), yield of porphyrin (UV–Vis), yield of N-confused porphyrin (HPLC), and level of unreacted aldehyde (TLC). Experiments were performed with benzaldehyde and pyrrole with catalysis by TFA or BF3–Et2O. Key observations include the following. (1) Reactions with BF3–Et2O exhibited reversible exchange of oligomers throughout the reaction. With TFA, the oligomer exchange processes were reversible at short reaction times, but became largely irreversible over the course of several hours. (2) The BF3–Et2O activity declined during the course of the reaction, whereas that of TFA was little changed. (3) The reaction medium remained homogeneous at 10 mM pyrrole + aldehyde. (4) Dipyrromethanes comprised of α- but not β-linkages underwent cleavage with either TFA or BF3–Et2O. (5) Condensations with carbinol intermediates (pyrrole-carbinol, dipyrromethane-monocarbinol, dipyrromethane-dicarbinol) provided rapid reactions, lower yields of porphyrin, and longer oligomers than typical in reactions of pyrrole + benzaldehyde. Higher porphyrin yields were obtained with BF3–Et2O than TFA, which is attributed to the more facile recovery from longer oligomers with the former versus the latter catalyst. Collectively, these and other observations lead to a model for the aldehyde + pyrrole condensation comprised of a combination of irreversible and reversible reactions in oligomer formation, irreversible side reactions (formation of dipyrrins, β-linkages), and slow inactivation of the catalyst (BF3–Et2O).

Alternate Syntheses Of Pyrromethanes And Porphyrins Using Acid-Modified Montmorillonite K-10 Clay

A variety of porphyrins and pyrromethanes are prepared using Montmorillonite clay mixed with a variety of acids (p-TsOH, BF3 Et2O).The ease of use of the naturally occurring clay as a co-catalyst makes it an attractive reagent for use in synthesis.

One-Pot Diels-Alder Reaction of N-p-Tosylaldimines Generated by BF3-Et2O Catalyzed Transformation of Naphtho[1,8-de]dithiin-1-N-p-tosylsulfilimines

Naphtho[1,8-de]dithiin-1-N-p-tosylsulfilimines (4) were prepared by the reaction of naphtho[1,8-de]dithiin with chloramine-T. Treatment of 4 with dienes in the presence of BF3Et2O afforded the imino Diels-Alder products via N-p-tosylaldimines produced in situ.

Synthesis of a new ortho- tert-butylphenol-based calix[4]arene

The ortho- tert-butylphenol derived calix[4]arene 5 with the OH groups arranged in a extra-annular fashion is synthesized by condensation of 2,2′-dihydroxy-3,3′-di- tert-butyldiphenylmethane 4 with formaldehyde under BF 3Et 2O catalysis. The crucial role of tert-butyl groups in promoting the macrocyclization process is emphasized.

A reaction of γ-chalcogen-substituted prop-2-ynyl cations with mild nucleophiles

γ-Chalcogen-substituted prop-2-ynyl cations are generated by the reactions of diethyl acetals 1 and 2 with BF3–Et2O and react with various mild nucleophiles without isomerisation to allenyl cations to afford the prop-2-ynylated products 3a–e and 5a–c in good yields.