Exclusive Solvent-Controlled Regioselective Catalytic Synthesis of Potentially Bioactive Imidazolidineiminodithiones: NMR Analysis, Computational Studies and X-ray Crystal Structures.

Herein, we describe the first consistent regiospecific reaction of isothiocyanates with a variety of substituted N-arylcyanothioformamides in a 1:1 molar ratio to generate a series of imidazolidineiminodithiones decorated with a multitude of functional groups on both aromatic rings. The reaction is carried out at room temperature using a 20 mol% catalytic amount of triethylamine with DMF as the solvent to selectively form the mentioned products with exclusive regioselectivity. The methodology features wide substrate scope, no requirement for chromatography, and good to high reaction yields. The products were isolated by simple ether/brine extraction and the structures were verified by multinuclear NMR spectroscopy and high accuracy mass measurements. The first conclusive molecular structure elucidation of the observed regioisomer was established by single-crystal X-ray diffraction analysis. Likewise, the tautomer of the N-arylcyanothioformamide reactant was proven by X-ray diffraction analysis. Density functional theory computations at the B3LYP-D4/def2-TZVP level in implicit DMF solvent were conducted to support the noted regiochemical outcome and proposed mechanism.

First Exclusive Stereo- and Regioselective Preparation of 5-Arylimino-1,3,4-Selenadiazole Derivatives: Synthesis, NMR analysis, and Computational Studies.

Isoselenocyanates are valuable coupling partners required for preparing key chemical intermediates and biologically active molecules in an accelerated and effective way. Likewise, (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides have been employed in numerous one-step heteroannulation reactions to assemble the structural core of several various kinds of heterocyclic compounds. Here, we describe the inverse electron demand 1,3-dipolar cycloaddition reaction of isoselenocyanates with a variety of substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides to generate, regioselectively and stereoselectively, a series of 5-arylimino-1,3,4-selenadiazole derivatives comprising a multitude of functional groups on both aryl rings. The synthetic method features gentle room-temperature conditions, wide substrate scope, and good to high reaction yields. The selenadiazoles were separated by gravity filtration in all instances and chemical structures were validated by multinuclear NMR spectroscopy and high accuracy mass spectral measurements. First conclusive molecular structure elucidation of the observed 5-arylimino-selenadiazole regioisomer was verified by single-crystal X-ray diffraction analysis. Crystal-structure measurement was successfully carried out on (Z)-1-(4-(4-iodophenyl)-5-(p-tolylimino)-4,5-dihydro-1,3,4-selenadiazol-2-yl)ethan-1-one and (Z)-1-(5-((4-methoxyphenyl)imino)-4-(4-(methylthio)phenyl)-4,5-dihydro-1,3,4-selenadiazol-2-yl)ethan-1-one. Likewise, the (Z)-geometry of the hydrazonoyl chloride reactant was proven by X-ray diffraction studies. As representative examples, crystal-structure determination was carried out on (Z)-2-oxo-N-phenylpropanehydrazonoyl chloride and (Z)-N-(3,5-bis(trifluoromethyl)phenyl)-2-oxopropanehydrazonoyl chloride. Density functional theory calculations at the B3LYP-D4/def2-TZVP level were conducted to support the noted experimental findings and suggested mechanism.

First X-ray Crystal Structure Characterization, Computational Studies, and Improved Synthetic Route to the Bioactive 5-Arylimino-1,3,4-thiadiazole Derivatives.

N-arylcyanothioformamides are useful coupling components for building key chemical intermediates and biologically active molecules in an expedited and efficient manner. Similarly, substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides have been utilized in numerous one-step heteroannulation reactions to assemble the structural core of several different types of heterocyclic compounds. Herein, we demonstrate the effectiveness of the reaction of N-arylcyanothioformamides with various substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides to produce, stereoselectively and regioselectively, a range of 5-arylimino-1,3,4-thiadiazole derivatives decorated with a multitude of functional groups on both aromatic rings. The synthetic methodology features mild room-temperature conditions, large substrate scope, wide array of functional groups on both reactants, and good to high reaction yields. The products were isolated by gravity filtration in all cases and structures were confirmed by multinuclear NMR spectroscopy and high accuracy mass spectral analysis. Proof of molecular structure of the isolated 5-arylimino-1,3,4-thiadiazole regioisomer was obtained for the first time by single-crystal X-ray diffraction analysis. Crystal-structure determination was carried out on (Z)-1-(5-((3-fluorophenyl)imino)-4-(4-iodophenyl)-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one and (Z)-1-(4-phenyl-5-(p-tolylimino)-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one. Similarly, the tautomeric structures of the N-arylcyanothioformamides and (Z)-geometries of the 2-oxo-N-phenylpropanehydrazonoyl chloride coupling partners were proven by X-ray diffraction studies. As representative examples, crystal-structure determination was carried out on (4-ethoxyphenyl)carbamothioyl cyanide and (Z)-N-(2,3-difluorophenyl)-2-oxopropanehydrazonoyl chloride. Density functional theory calculations at the B3LYP-D4/def2-TZVP level were carried out to rationalize the observed experimental findings.

A Concise Synthesis of Pyrrole-Based Drug Candidates from α-Hydroxyketones, 3-Oxobutanenitrile, and Anilines.

A simple and concise three-component synthesis of a key pyrrole framework was developed from the reaction between α-hydroxyketones, oxoacetonitriles, and anilines. The synthesis was used to obtain several pyrrole-based drug candidates, including COX-2 selective NSAID, antituberculosis lead candidates BM212, BM521, and BM533, as well as several analogues. This route has potential to obtain diverse libraries of these pyrrole candidates in a concise manner to develop optimum lead compounds.

Selective One-Pot Multicomponent Synthesis of N-Substituted 2,3,5-Functionalized 3-Cyanopyrroles via the Reaction between α-Hydroxyketones, Oxoacetonitriles, and Primary Amines.

A one-step, three-component reaction between α-hydroxyketones, oxoacetonitriles, and primary amines gives N-substituted 2,3,5-functionalized 3-cyanopyrroles with complete selectivity in up to 90% isolated yields. The reaction worked on a wide substrate scope under mild reaction conditions (AcOH as a catalyst, EtOH, 70 °C, 3 h). The reaction proceeded with very high atom efficiency as water is the only molecule lost during the reaction. The practicality of the reaction was demonstrated on a large gram scale. The structures of the 3-cyanopyrroles were confirmed by single-crystal X-ray diffraction and NMR; this work provides a general and practical entry to pyrrole scaffolds suitably decorated for the synthesis of various bioactive pyrroles in a concise manner.

Selective One-Pot Cascade Synthesis of N-Substituted Highly Functionalized Pyrroles from Unprotected Sugars, Primary Amines, and Oxoacetonitriles.

A one-pot, three-component cascade reaction between unprotected sugars, primary amines, and 3-oxoacetonitriles gave N-substituted 2,3,5-functionalized pyrroles or N-substituted 2,3,4-functionalized pyrroles in excellent yields and selectivities. The selectivity of the reaction was achieved by simple control of the sequence of substrate addition. The reaction showed a wide substrate scope, and various types of sugars, primary amines, and oxoacetonitriles reacted smoothly. The work demonstrates a highly desired simple reaction for embedding nitrogen into sugars to produce valuable N-heterocyclic compounds that are amenable to further modifications to natural products and drug intermediates.

Iodine-DMSO mediated conversion of N-arylcyanothioformamides to N-arylcyanoformamides and the unexpected formation of 2-cyanobenzothiazoles.

Cyanoformamides are ubiquitous as useful components for assembling key intermediates and bioactive molecules. The development of an efficient and simple approach to this motif is a challenge. Herein, we demonstrate the effectiveness of the I2-DMSO oxidative system in the preparation of N-arylcyanoformamides from N-arylcyanothioformamides. The synthetic method features mild conditions, broad substrate scope, and high reaction efficiency. Furthermore, this method provides an excellent entry to exclusively afford 2-cyanobenzothiazoles which are useful substrates to access new luciferin analogs. The structures of all new products were elucidated by multinuclear NMR spectroscopy and high accuracy mass spectral analysis. Crystal-structure determination by means of single-crystal X-ray diffraction was carried out on (4-bromophenyl)carbamoyl cyanide, 5,6-dimethoxybenzo[d]thiazole-2-carbonitrile, 5-(benzyloxy)benzo[d]oxazole-2-carbonitrile, 4,7-dimethoxybenzo[d]thiazole-2-carbonitrile, and (5-iodo-2,4-dimethoxyphenyl)carbamoyl cyanide, a key intermediate with mechanistic implications.

Synthesis, α-glucosidase inhibition, α-amylase inhibition, and molecular docking studies of 3,3-di(indolyl)indolin-2-ones.

The synthesized 3,3-di(indolyl)indolin-2-ones 1a-p showed desired higher α-glucosidase inhibitory activities and lower α-amylase inhibitory activities than standard drug acarbose. Particularly, compound 1i showed favorable higher α-glucosidase % inhibition of 67 ± 13 and lower α-amylase % inhibition of 51 ± 4 in comparison to acarbose with % inhibition activities of 19 ± 5 and 90 ± 2, respectively. Docking studies of selected 3,3-di(indolyl)indolin-2-ones revealed key interactions with the active sites of both α-glucosidase and α-amylase, further supporting the observed % inhibitory activities. Furthermore, the binding energies are consistent with the % inhibition values. The results suggest that 3,3-di(indolyl)indolin-2-ones may be developed as suitable Alpha Glucosidase Inhibitors (AGIs) and the lower α-amylase activities should be advantageous to reduce the side effects exhibited by commercial AGIs.

Targeted Synthesis of 3,3'-, 3,4'- and 3,6'-Phenylpropanoid Sucrose Esters.

In this study, we report on an orthogonal strategy for the precise synthesis of 3,3'-, 3,4'-, and 3,6'-phenylpropanoid sucrose esters (PSEs). The strategy relies on carefully selected protecting groups and deprotecting agents, taking into consideration the reactivity of the four free hydroxyl groups of the key starting material: di-isopropylidene sucrose 2. The synthetic strategy is general, and potentially applies to the preparation of many natural and unnatural PSEs, especially those substituted at 3-, 3'-, 4'- and 6'-positions of PSEs.

Chemistry of trisindolines: natural occurrence, synthesis and bioactivity.

Heterocyclic nitrogen compounds are privileged structures with many applications in the pharmaceutical and nutraceutical industries since they possess wide bioactivities. Trisindolines are heterocyclic nitrogen compounds consisting of an isatin core bearing two indole moieties. Trisindolines have been synthesized by reacting isatins with indoles using various routes and the yield greatly depends on the catalyst used, reaction conditions, and the substituents on both the isatin and indole moieties. Amongst the synthetic routes, acid-catalyzed condensation reaction between isatins and indoles are the most useful due to high yield, wide scope and short reaction times. Trisindolines are biologically active compounds and show anticancer, antimicrobial, antitubercular, antifungal, anticonvulsant, spermicidal, and antioxidant activities, among others. Trisindolines have not previously been reviewed. Therefore, this review aims to provide a comprehensive account of trisindolines including their natural occurrence, routes of synthesis, and biological activities. It aims to inspire the discovery of lead trisindoline drug candidates for further development.

A Practical Synthesis of Densely Functionalized Pyrroles via a Three-Component Cascade Reaction between Carbohydrates, Oxoacetonitriles, and Ammonium Acetate.

A practical three-component reaction between unactivated carbohydrates, oxoacetonitriles, and ammonium acetate gave densely functionalized pyrroles in 75-96% yields. Disaccharides afforded novel pyrrolo-glycosides. This metal-free, Et3N-catalyzed cascade reaction proceeded with exclusive chemo-, regio-, and stereoselectivities and showed a wide substrate scope with high atom economy. It also proceeded successfully at a 2 g scale, demonstrating potential for large-scale synthesis. The functional groups on the pyrroles permit easy transformation to other handles for the construction of more complex structures. The reaction proceeded through a cascade mechanism involving several intermediates identified by mass spectrometric analysis. This work has great potential for the sustainable production of densely functionalized pyrroles from cheap and widely available carbohydrates and represents a key advancement in the sustainable synthesis of these ubiquitous heterocycles.

TMSOTf-Promoted Intermolecular Cascade Reaction of Aromatic Diazo Ketones with Olefins: Selective Synthesis of 3-Arylethylideneoxindoles.

A simple trimethylsilyl trifluoromethanesulfonate (TMSOTf)-promoted intermolecular cascade reaction of aromatic diazo ketones with olefins has been developed. This method directly gave 3-phenylethylideneoxindoles from 3-diazooxindoles and styrenes with exclusive regioselectivity, chemoselectivity, and E-stereoselectivity. The key to the success of the reaction and higher yields is the elegant use of TMSOTf, which gradually released the active triflic acid promoter in situ. The reaction tolerates a wide substrate scope of 3-diazooxindoles and styrenes with electron-donating and electron-withdrawing groups and works well on the gram scale.

Perfluorophenylboronic acid-catalyzed direct α-stereoselective synthesis of 2-deoxygalactosides from deactivated peracetylated d-galactal.

Perfluorophenylboronic acid 1c catalyzes the direct stereoselective addition of alcohol nucleophiles to deactivated peracetylated d-galactal to give 2-deoxygalactosides in 55-88% yield with complete α-selectivity. The unprecedented results reported here also enable the synthesis of disaccharides containing the 2-deoxygalactose moiety directly from the deactivated peracetylated d-galactal. This convenient and metal-free glycosylation method works well with a wide range of alcohol nucleophiles as acceptors and tolerates a range of functional groups without the formation of the Ferrier byproduct and without the need for a large excess of nucleophiles or additives. The method is potentially useful for the synthesis of a variety of α-2-deoxygalactosides.

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides.

A convenient protocol was developed for the synthesis of 2,3-unsaturated C-, O-, N- and S-linked glycosides (enosides) using 20 mol % perflurophenylboronic acid catalyst via Ferrier rearrangement. Using this protocol, D-glucals and L-rhamnals reacted with various C-, O-, N- and S-nucleophiles to give a wide range of glycosides in up to 98% yields with mainly α-anomeric selectivity. The perflurophenylboronic acid successfully catalyzed a wide range of substrates (both glucals and nucleophiles) under very mild reaction conditions.

Polymer-supported triphenylphosphine: application in organic synthesis and organometallic reactions.

This comprehensive review highlights the diverse chemistry and applications of polymer-supported triphenylphosphine (PS-TPP) in organic synthesis since its inception. Specifically, the review describes applications of the preceding reagent in functional group interconversions, heterocycle synthesis, metal complexes and their application in synthesis, and total synthesis of natural products. Many examples are provided from the literature to show the scope and selectivity (regio, stereo, and chemo) in these transformations.

Impact of the type of emulsifier on the physicochemical characteristics of the prepared fish oil-loaded microcapsules.

Fish oil microcapsules were successfully prepared from fish oil-in-water emulsions using chitosan as shell material and anionic surfactants sodium dodecyl sulphate (SDS), sodium dodecylbenzenesulfonate (SDBS), sodium cholate (cholate), and sodium deoxycholate (DOC) as emulsifiers. The type of emulsifier influenced the physicochemical characteristics of the prepared microcapsules to different extents. The microcapsules formed with DOC showed the least mean effective diameter (MED) of 500 nm. Emulsion formed with DOC exhibited the smallest MED of 100 nm. The emulsions showed negative zeta potential values which became positive after encapsulation with chitosan. The surfactants showed little influence on thermal stability. Microcapsule suspensions showed creaming over storage. Fish oil at higher loading in SDS microcapsules showed higher primary and secondary oxidation. All microcapsules showed sustained release but the values varied depending upon the surfactants. The emulsion and microcapsules formed with DOC showed better morphology and stability despite its lower loading and encapsulation efficiency.

Total synthesis of phenylpropanoid glycoside osmanthuside-B6 facilitated by double isomerisation of glucose-rhamnose orthoesters.

A convenient synthesis of phenylpropanoid glycoside osmanthuside-B6 is disclosed. The key steps involved regioselective coumaroylation and rhamnosylation of unprotected phenylethyl-ß-d-glucopyranoside to give 2- and 3-O-rhamnosyl orthoester glucopyranosides. Rearrangement of these orthoesters followed by selective removal of their acetyl and allyl groups gave osmanthuside-B6 in 22% overall yield. The rearrangement involved a newly discovered glucose-rhamnose orthoester double isomerization process that has the potential to provide a convenient access to many complex phenylpropanoid glycosides. The synthetic route developed is envisioned to serve as a model for the preparation of phenylpropanoid glucosides having a (substituted) cinnamoyl moiety at O-6 and a saccharide moiety at O-3.

Short synthesis of phenylpropanoid glycoside grayanoside-A and analogues.

A short synthesis of phenylethyl glycosides grayanoside-A 1, 2 and analogues 3-4 in high 43-65% overall yields is described. The main synthetic step involved regioselective O-6 acylation of unprotected 2-phenylethyl-ß-D-glucoside 7 with cinnamoyl chlorides 8a-d using Me2SnCl2 as catalyst. The acylation at O-6 is regioselective regardless of the type of cinnamoyl chloride used. Protection/deprotection steps of the glucoside core were not necessary. The synthetic route is generally applicable for the synthesis of phenylpropanoid glycoside class of compounds acylated at O-6.

Encapsulation of fish oil with N-stearoyl O-butylglyceryl chitosan using membrane and ultrasonic emulsification processes.

Fish oil-loaded microcapsules were prepared from oil-in-water emulsions using N-stearoyl O-butylglyceryl chitosan as shell material. The emulsions were prepared by both membrane and ultrasonic emulsification processes under variable conditions to examine the effect of the emulsification process and encapsulation conditions on the characteristics of the microcapsules. The microcapsules were characterized with respect to their morphologies, colloidal stability, loading capacity, encapsulation efficiency and release profile. The microcapsules formed by the membrane emulsification process exhibited larger diameter compared to those from the ultrasonic emulsification process which gave a mean effective diameter of ≈1µm. The microcapsules obtained by membrane emulsification process gave better loading capacity and encapsulation efficiency. The microcapsules from both processes showed sustained release of fish oil and the release profile depended on the type of the process. TGA confirmed that encapsulation using N-stearoyl O-butylglyceryl chitosan impeded heat transfer and significantly increased the thermal stability of the encapsulated fish oil.

Synthesis, characterization and the antimicrobial activity of new eco-friendly ionic liquids.

A green microwave-assisted procedure for the preparation of a series of 24 new 1-alkyl-3-ethylimidazolium ionic liquids with different functional groups in the alkyl chain is described. Moreover, the synthesis of a variety of ten new geminal dicationic ionic liquids is reported. Their structures were characterized by FT-IR, (1)H NMR, (13)C NMR, (11)B, (19)F, (31)P, and mass spectrometry. Several ionic liquids were selected for antimicrobial activity studies, yielding very interesting and promising results.