Aminoalkylation with Aldehydes Mediated by Solid Lithium Perchlorate

Summary. The solid LiClO₄-mediated one-pot reaction of aldehydes with secondary amines and C nucleophiles afforded the corresponding aminoalkylation products in high yields. Unlike the previous reported procedure, the aminoalkylation of aldehyde was achieved in the presence of only 0.5 equivalents of solid lithium perchlorate in dichloromethane as the solvent with good to high yields at room temperature.     

Direct aminoalkylation of cycloalkanes through dimethylzinc-initiated radical process

Cycloalkyl radicals were directly generated from cycloalkanes via C-H bond cleavage by the action of dimethylzinc-air and underwent an addition reaction with N-tosylimines, giving aminoalkylation products in fair to high yields.     

Triflic acid-catalyzed highly stereoselective friedel-crafts aminoalkylation of indoles and pyrroles

A simple and efficient synthesis to both enantiomers of highly enantiomerically enriched alpha-trifluoromethyl-alpha-(heteroaryl)-glycine derivatives via highly stereoselective aminoalkylation of indoles and pyrroles is described. The triflic acid-catalyzed reaction of enantiomeric 3,3,3-trifluoro-pyruvate-alpha-methylbenzyl imines with indoles and pyrroles and the subsequent Pd-catalyzed hydrogenolysis of the methylbenzyl group provided the products in high yields and excellent enantioselectivities.     

Microwave Promoted Rapid Dehydration of Aldoximes to Nitriles on a Solid Support †

Aldoximes undergo rapid dehydration with H₂SO₄/ SiO₂ solid support, under microwave irradiation in dry media to afford nitriles in high yields.

     

Stereoselective allylation of aldehydes on solid support and its application in biology-oriented synthesis (BIOS)

A systematic study on the asymmetric allylation of aldehydes on solid support is reported. Different kinds of chiral allylboron reagents with complementary direction of stereoinduction were applied successfully in this reagent-controlled transformation. The homoallylic alcohol products are generated with high levels of stereoselectivity and in high yields. The crotylation of aldehydes on solid support employing (E)- and (Z)-Ipc₂crotylborane also proceeds with very high levels of stereoinduction and in high yields. Applications of this methodology for the synthesis of compound collections by subsequent modifications of the allylic moiety are described. In particular, a collection of γ- and δ-lactones has been synthesized by means of a cyclo-release approach including a natural product. In addition, a procedure for the long-standing problem of the hydrogenation of double bonds on solid support is reported. We have also demonstrated the feasibility of applying the stereoselective allylation of aldehydes on solid support in an iterative fashion to generate polyol structures.     

Gold-nanoparticle-catalyzed synthesis of propargylamines: the traditional A3-multicomponent reaction performed as a two-step flow process

The alkyne, aldehyde, amine A(3)-coupling reaction, a traditional multicomponent reaction (MCR), has been investigated as a two-step flow process. The implicated aminoalkylation reaction of phenylacetylene with appropriate aldimine intermediates was catalyzed by gold nanoparticles impregnated on alumina. The aldimine formation was catalyzed by Montmorillonite K10 beforehand. The performance of the process has been investigated with respect to different reaction regimes. Usually, the A(3)-multicomponent reaction is performed as a "one-pot" process. Diversity-oriented syntheses using MCRs often have the shortcoming that only low selectivity and low yields are achieved. We have used a flow-chemistry approach to perform the A(3)-MCR in a sequential manner. In this way, the reaction performance was significantly enhanced in terms of shortened reaction time, and the desired propargylamines were obtained in high yields.     

New deprotection method of the 2,2,2-trichloroethoxycarbonyl (Troc) group with (Bu3Sn)2

The 2,2,2-trichloroethoxycarbonyl (Troc) group was efficiently removed in high yields with (Bu₃Sn)₂ in DMF under microwave heating. The present method was applied to deprotection of the Troc group on solid support.     

Ring‐Shaped Silafluorene Derivatives as Efficient Solid‐State UV‐Fluorophores: Synthesis,Characterization, and Photoluminescent Properties

Four ring‐shaped silafluorene‐containing compounds ( 1 – 4 ) were synthesized and characterized as potentially promising monomers for fluorescent polymers. Their optical properties in solution and solid state (thin film and powder) were studied. These compounds have low quantum yields in solution (Φ_fl=0.13‐0.15) with fluorescence maxima at about 355 nm, but high quantum yields in the solid state (powder, Φ_fl=0.35‐0.54) with fluorescence maxima at about 377 and 488 nm. Influence of the substituents and the number of silafluorene units in 1 – 4 on their optical properties was investigated. Extensive study of the X‐ray crystal structures of 1 – 4 was undertaken to analyze and qualitatively estimate the role, extent, and influence of silafluorene moieties’ interactions on solid‐state fluorescent properties. Excited state UV/Vis and theoretical molecular orbital (MO) calculations were performed to explore possible fluorescence mechanisms and differences in quantum yields among these compounds.     

A mild and highly efficient protocol for the one-pot synthesis of primary α-amino phosphonates under solvent-free conditions

Under solvent-free reaction conditions and in the presence of solid LiClO₄ a novel and mild protocol for the one-pot, three-component synthesis of primary α-amino phosphonates from an aldehyde, hexamethyldisilazane and a trialkyl phosphite is described giving high yields and having short reaction times. The same products are obtained in very low yields, when the three-component reaction is carried out under microwave irradiation and in the absence of solid LiClO₄. Examples of some prepared 1-aryl-N,N′-bis(arylidene)methanediamines are also described.     

Alkylation of 3-Acetylthiophene Under Phase-Transfer Conditions

Reactions of 3-acetylthiophene with C₁-C₄-alkyl iodides in a two-phase benzene/solid KOH system in the presence of l8-crown-6 afford di-C-alkylated derivatives-(3-thienyl)COCHR₂ in satisfactory yields (～50%) with high regioselectivity (70–100%).     

Dark Fermentative Hydrogen Production from Neutralized Acid Hydrolysates of Conifer Pulp

Concentrated acid hydrolysis of cellulosic material results in high dissolution yields. In this study, the neutralization step of concentrated acid hydrolysate of conifer pulp was optimized. Dry conifer pulp hydrolysis with 55?% H₂SO₄ at 45?°C for 2?h resulted in total sugar yields of 22.3?C26.2?g/L. The neutralization step was optimized for solid Ca(OH)₂, liquid Ca(OH)₂ or solid CaO, mixing time, and water supplementation. The highest hydrogen yield of 1.75?mol?H₂/mol glucose was obtained with liquid Ca(OH)₂, while the use of solid Ca(OH)₂ or CaO inhibited hydrogen fermentation. Liquid Ca(OH)₂ removed sulfate to below 30?mg SO₄ ^2?/L. Further optimization of the neutralization conditions resulted in the yield of 2.26?mol?H₂/mol glucose.     

An environmentally friendly,chemoselective, and efficient protocol for the preparation of coumarin derivatives by Pechman condensation reaction using new and reusable heterogeneous Lewis acid catalyst polystyrene-supported GaCl3

An environmentally benign Pechman protocol for the one-pot synthesis of 4-substituted coumarins through the condensation reactions of phenol substrates with β-ketoesters using polystyrene-supported GaCl₃ (PS–GaCl₃) as a highly active and reusable solid Lewis acid catalyst under mild and heterogeneous conditions in good to excellent yields is described. This new protocol is easy, simple, cost-effective, chemoselective, and in addition has the advantages of easy availability, stability, reusability and eco-friendly character of the catalyst, high to excellent yields, simple experimental and work-up procedure.     

Nano-BF<Subscript>3</Subscript>·SIO<Subscript>2</Subscript>: a reusable and eco-friendly catalyst for synthesis of quinoxalines

2,3-Disubstituted quinoxalines were synthesized via condensation of α-diketones and 1,2-phenylenediamines. Nano-BF₃·SiO₂ as a "green" and reusable solid acid was used as the catalyst for the synthesis of quinoxalines. The reaction was carried out at room temperature under sonication with high to excellent yields.     

Solvent‐Free Iodination of Arenes using Iodine–Silver Nitrate Combination

A simple and environmentally safe general method of iodination of aromatic substrates under sovent‐free conditions using the I₂/AgNO₃ combination in a solid state is reported. Both activated and deactivated aromatic compounds afford the respective aryl iodides in generally high yields (80–90%).     

Highly Emissive Diborylphenylene‐Containing Bis(phenylethynyl)benzenes: Structure–Photophysical Property Correlations and Fluoride Ion Sensing

A series of 2,5‐bis(dimesitylboryl)‐1,4‐bis(arylethynyl)benzenes 1 – 6 that contain various p‐substituents on the terminal benzene rings, including NPh₂ ( 1 ), OMe ( 2 ), Me ( 3 ), H ( 4 ), CF₃ ( 5 ), and CN ( 6 ) groups, were synthesized, and the effects of the p‐substituents on the absorption and fluorescence properties were investigated both in solution and in the solid state. Linear relationships were obtained not only between the Hammett σ_p⁺ constants of the p‐substituents and the absorption and fluorescence maxima, quantum yields, and excited‐state dynamics parameters in solution, but also between the σ_p⁺ constants and the fluorescence quantum yields in the solid state. An important finding extracted from these results is that the suppressed fluorescence quenching in the solid state is a common feature for the present laterally boryl‐substituted π‐conjugated skeletons. Hence, the diborylphenylene can serve as a useful core unit to develop highly emissive organic solids. In fact, most of the derivatives showed more intense emission in the solid state than in solution. In addition to these studies, the titration experiment of 1 by the addition of nBu₄NF was conducted, which showed the stepwise bindings of two fluoride ions with high association constants as well as a drastic change in the fluorescence spectra, while constantly maintaining high quantum yields (0.61–0.76), irrespective of the binding modes. This result also demonstrated the potential utility of the present molecules as an efficient fluorescent fluoride ion sensor.     

Ca(HSO4)2 mediated conversion of alcohols into N-substituted amides under heterogeneous conditions: A modified Ritter reaction

Tertiary, secondary, and benzylic alcohols react efficiently with nitriles in the presence of the catalyst calcium hydrogen sulfate, Ca(HSO₄)₂, to produce amides in high yields. In this study, a modified Ritter reaction using this solid acid catalyst is found to be an environmentally safe method for converting 2,6-bis(hydroxymethyl)-4-halo anisole into the corresponding diamides in CH₃CN.     

Microwave-assisted silica-supported aluminum chloride-catalyzed Friedel-Crafts alkylation

Microwave irradiation is a popular method in organic synthesis to achieve high yields in shorter reaction times. This decreases total ‘man-hours’ in a synthetic setting. Another technique used in organic chemistry to decrease manual manipulations, is solid support reagents. The benefits of this approach is that upon completion of a reaction, a simple filtration can be performed which expedites the work-up and also produces less organic waste. Friedel-Crafts alkylation has been explored using microwave chemistry as well as with solid-supported reagents. In comparison with traditional heating, as well as with AlCl₃, superior yields were observed with silica-gel bound aluminum chloride (Si-AlCl_x) when microwave irradiated for only 5 min.     

Synthesis of water-soluble cationic cellulose derivatives with tertiary amino groups

Water-soluble cellulose derivatives with tertiary amino groups up to substitution degree 0.8 (4.2% of coupled nitrogen) were prepared in a controlled manner by the interaction of cellulose acetate with N,N-diethylepoxypropylamine. It was shown that two reactions take place simultaneously, i.e., hydrolysis of acetyl groups and aminoalkylation of free hydroxyl groups of cellulose. The amino groups coupled to the cellulose are of middle basicity with pK _α ~9.5. Solubility of the products was found to be determined by the chemical composition of the cellulose derivative.     

Synthesis of (Z)-organylthioenynes using KF/Al2O3/solvent as recyclable system

PEG-400 and glycerol were successfully used as recyclable solvents for the synthesis of several organylthioenynes in good to excellent yields and high selectivity using solid supported catalyst (KF/Al₂O₃). This easy, general and improved method furnishes the corresponding alkenyl sulfides preferentially with Z configuration. The catalytic system and the glycerol or PEG-400 can be reused up to three times without previous treatment with comparable activity.     

Sulfated zirconia (SO4/ZrO2) as a reusable solid acid catalyst for the Mannich-type reaction between ketene silyl acetals and aldimines

Sulfated zirconia (SO₄/ZrO₂) catalyzed Mannich-type reactions of ketene silyl acetals and aldimines proceeded smoothly at room temperature to afford β-amino esters in good to high yields. In addition, the heterogeneous solid acid catalyst SO₄/ZrO₂ was easily recovered from the reaction mixture and then reused without significant loss of effectiveness.