Catalytic stereoselective Mannich reaction under solvent-free conditions

Silicon tetrachloride catalyzed one-pot three-component Mannich reaction of cyclic ketones, aromatic aldehydes, and aromatic amine under solvent-free conditions affords the corresponding β-amino ketones with excellent yield and good to excellent anti-selectivity.     

Facile preparation of aromatic ketones from aromatic bromides and arenes with aldehydes

Aromatic ketones were efficiently prepared in good yields by the reactions of aryl bromides with n-BuLi, followed by the reactions with aromatic aldehydes or aliphatic aldehydes and the subsequent treatment with molecular iodine and K₂CO₃, in a one-pot method. The same treatment of arenes, instead of aromatic bromides, also provided the corresponding aromatic ketones in good yields. Using these methods, various diaryl ketones and alkyl aryl ketones bearing electron-rich aromatics and electron-deficient aromatics could be prepared efficiently by a simple, transition-metal-free, and therefore environmentally benign experimental procedure.     

Sequential amination/annulation/aromatization reaction of carbonyl compounds and propargylamine: a new one-pot approach to functionalized pyridines

A general one-pot synthesis of pyridines 4a-t from the reaction of dialkyl acyclic/cyclic ketones 1a-i, methyl, aryl/heteroaryl ketones 1m-r, and aldehydes bearing alpha-hydrogens 1s,t with propargylamine 2 is described. Gold and copper salts are efficient catalysts for the reaction of ketones with 2. The formation of the pyridines 4 is suggested to proceed through the sequential amination of carbonyl compounds followed by regioselective 6-endo-dig cyclization of the N-propargylenamine (N-propargyldienamine) intermediate 3(5) and aromatization reaction. Whereas the preparation of linear polycyclic pyridine 4i can be carried out by reacting cholestan-3-one 1i with 2, the angular polycyclic pyridine 4j has been obtained starting from cholest-5-en-3-one 1j. Selectivity of the reaction of polycyclic dicarbonyls 1k,l with 2 has also been investigated.     

One-pot three-component reaction for the synthesis of pyran annulated heterocyclic compounds using DMAP as a catalyst

The one-pot three-component reaction for the synthesis of pyran annulated heterocycles is reported by condensing aromatic aldehydes, ethyl cyanoacetate, or malononitrile and C-H activated acidic compounds in the presence of catalytic amount of 4-(dimethylamino)pyridine (DMAP) in ethanol under reflux conditions. The significant features of the present protocol are simple, environmentally benign, high yields, non-aqueous work-up procedure, no chromatographic separation and recyclability of the catalyst.     

A new and facile tetrachlorosilane-promoted one-pot condensation for the synthesis of a novel series of tetracyclic 1,5-thiazepines

A new and facile approach for the one-pot synthesis of a novel series of tetracyclic 1,5-thiazepines is described. The reaction occurs through cyclocondensation of fused cyclic ketones, aromatic aldehydes, and 2-aminothiophenol using tetrachlorosilane as a promoter in methylene chloride at ambient temperature.     

Highly efficient one-pot, three-component Mannich reaction catalysed by boric acid and glycerol in water with major ‘syn’ diastereoselectivity

Boric acid and glycerol efficiently catalysed the one-pot, three-component Mannich reaction of aldehydes, aromatic amines and cyclic ketones in water at ambient temperature to afford the corresponding β-amino carbonyl compounds in good yields. All but one reaction proceeded with moderate ‘syn’ diastereoselectivity. This observation is just the reverse of the major anti diastereoselectivity obtained in most of the earlier reported procedures. The methodology is mild and efficient using minute quantities of catalyst with no side products and a very simple work-up procedure.     

Efficient NaOH-Catalyzed Reaction of Aromatic Aldehyde,Cyclic Ketones,and Malononitrile Under Solvent-Free Conditions Using a Grinding Method

An efficient and facile synthesis of 2,6-dicyanoanilines via a one-pot reaction of aromatic aldehydes, malononitrile, and cyclic ketones in the presence of NaOH under solvent-free conditions using a grinding method has been developed. Compared with the classical reaction conditions, the new synthetic method has the advantages of excellent yields, shorter reaction times, and mild reaction conditions.     

Zr(HSO4)4/SiO2: An effective heterogeneous alternative for one-pot synthesis of β-acetamido ketones

In a one-pot procedure, enolizable ketones reacted with aromatic aldehydes, acetyl chloride and acetonitrile at room temperature in the presence of Zr(HSO₄)₄/SiO₂ to furnish the corresponding β-acetamido ketones in improved yields.     

The methyl group as a source of structural diversity in heterocyclic chemistry: side chain functionalization of picolines and related heterocycles

The reaction of 2-picoline at the methyl group with NDA and KDA followed by dimethyldisulfide trapping furnished, respectively, dithioacetals and trithioortho esters with high selectivity. The method was successfully applied to other methyl-substituted pyridines, quinolines, and pyrazines. Dithioketals were prepared by a one-pot procedure involving the reaction of metalated 2-picoline with 2 equiv of dimethyldisulfide followed by in situ trapping with a second electrophile. All of the generated thio-substituted compounds were efficiently transformed in presence of mercury salts or under oxidizing conditions to other functional groups comprising aldehydes, ketones, ketals, thiol esters, orthoesters, and esters.     

An efficient four-component synthesis of dithiocarbamate derivatives

An environmentally benign, one-pot, four-component synthesis of chemically and pharmaceutically interesting dithiocarbamate derivatives is reported. The one-pot reaction of various aromatic aldehydes, ketones, aliphatic amines, and carbon disulfide, in the presence of potassium hydroxide in urea-choline chloride deep eutectic solvent or ethanol, leads to the corresponding dithiocarbamates in good to excellent yields. This method provides a convenient and time-saving strategy, with a simple work-up procedure.     

Copper-catalyzed three-component one-pot synthesis of quinazolines

Two efficient approaches to multi-substituted quinazolines by the three-component one-pot reaction of o-bromo aromatic ketones/aldehydes, ammonia water and aromatic aldehydes, or primary alcohols catalyzed by CuCl have been developed.     

Secondary amine catalyzed retro-aldol reactions of enals and enones: one-pot conversion of enals to α-substituted derivatives

A practical synthetic procedure to hydrolytically cleave the C,C-double bond of α,β-unsaturated aldehydes and ketones has been developed. Secondary amines are employed as organocatalysts for the retro-aldol process under simple and mild reaction conditions. Beside the generation of the parent aromatic aldehydes, the synthetic procedure has been successfully used in a one-pot reaction sequence to convert simple cinnamaldehydes into their α-aryl/alkyl substituted derivatives.     

Chemoselective annulation of 1,3-dithiin, -thiazine and -oxathiin rings on thiazoles using a green protocol

Tandem Knoevenagel and Michael reactions of 3-arylrhodanines, aromatic aldehydes and ammonium N-aryldithiocarbamates diastereoselectively yield dithioesters, thiazol-5-ylmethyl N-aryldithiocarbamates, under solvent-free microwave irradiation conditions in a one-pot procedure. Under the same conditions, the dithioesters are chemoselectively and expeditiously annulated with montmorillonite K-10 clay, Li⁺-montmorillonite clay and I₂ to give thiazolo-1,3-dithiins, -thiazines and -oxathiins, respectively.     

The NHCs-mediated cross-coupling of aromatic aldehydes with benzyl halides: synthesis of α-aryl ketones

A new NHCs-mediated synthetic method was found to produce α-aryl ketones in 22-63% yields in one-pot process from the corresponding aromatic aldehydes and benzyl halides. This method is the first example of the NHCs-mediated intermolecular nucleophilic acylation of aromatic aldehydes with benzyl halides.     

Bismuth(III) chloride-catalyzed one-pot Mannich reaction: three-component synthesis of β-amino carbonyl compounds

A simple and efficient method has been developed for the one-pot Mannich reaction of β-amino carbonyl compounds from aromatic aldehydes, aromatic ketones and aromatic amines in the presence of a catalytic amount of bismuth trichloride.     

Highly efficient one-pot three-component Mannich reaction in water catalyzed by heteropoly acids

[reaction: see text] Heteropoly acids efficiently catalyzed the one-pot, three-component Mannich reaction of ketones with aromatic aldehydes and different amines in water at ambient temperature and afforded the corresponding beta-amino carbonyl compounds in good to excellent yields and with moderate diastereoselectivity. This method provides a novel and improved modification of the three-component Mannich reaction in terms of mild reaction conditions and clean reaction profiles, using very a small quantity of catalyst and a simple workup procedure.     

Proline-Catalyzed Simple and Efficient Synthesis of 1,8-Dioxo-decahydroacridines in Aqueous Ethanol Medium

Proline-catalyzed synthesis of 1,8-dioxo-decahydroacridines is achieved via one-pot, three-component condensation of aromatic aldehydes, cyclic diketone, and aryl amines in aqueous ethanol medium. This method offers the advantages of proceeding in neutral and mild conditions, giving high to excellent yields of acridines with easy workup procedure.     

One-pot synthesis of ω-bromoesters from aromatic aldehydes and diols using pyridinium hydrobromide perbromide

A simple and efficient one-pot procedure has been developed for the synthesis of ω-bromoesters from aromatic aldehydes and diols in the presence of pyridinium hydrobromide perbromide (PHPB) and triethoxymethane in which aldehyde reacts first with diol and the product, cyclic acetal, reacts with PHPB to give the final product, ω-bromoesters.     

Unexpected cascade transformations in the reaction of aromatic aldehydes with the malononitrile dimer

The one-pot reaction of aromatic aldehydes, malononitrile dimer, and triethylamine unexpectedly led to ammonium salts of not previously assumed 5,7-diamino-4-aryl-2-(dicyanomethyl)-1,4-dihydro-1,8-naphthyridine-3,6-dicarbonitriles, but the isomeric 5,7-diamino-4-aryl-2-(dicyanomethyl)-1,4-dihydro-1,6-naphthyridine-3,8-dicarbonitriles. Following neutralization and dehydrogenation led to the new, annulated with pyridine ring tricyanopyridines (TCPy).     

One-pot synthesis of 1,5-diketones catalyzed by barium isopropoxide

A tandem cross-coupling reaction of aryl methyl ketones with aromatic aldehydes has been accomplished employing barium isopropoxide as a catalyst, in which barium enolates are generated and then three consecutive reactions (aldol reaction/β-elimination/conjugate addition) occur; this one-pot procedure is a convenient method to obtain symmetrical 1,5-diketones in good yields. In some cases, addition of iso-propanol is effective in improving the chemical yield.