Palladium-bipyridine catalyzed conjugate addition of arylboronic acids to α,β-unsaturated carbonyl compounds in aqueous media

Palladium/bipyridine catalyzed conjugate addition of arylboronic acids to α,β-unsaturated carbonyl compounds in aqueous media was developed with high yields.     

Radical promoted cyclizations of aromatic carbonyl compounds to benzopyrans using titanocene(III) chloride

Aromatic carbonyl compounds undergo smooth intramolecular radical cyclization with alkenes or alkynes using titanocene(III) chloride to furnish the corresponding benzopyrans. The radical initiator, Cp₂TiCl, was prepared in situ from commercially available titanocene dichloride (Cp₂TiCl₂) and zinc dust in THF under argon.     

Iodine-catalyzed efficient conjugate addition of pyrroles to α,β-unsaturated ketones

Iodine was used as a catalyst for the conjugate addition of pyrroles to α,β-unsaturated ketones at room temperature. Mono- and dialkylated products were obtained by using equimolar amounts of the reactants. However, the use of excess enones afforded only dialkylated products.     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for Michael addition of mercaptans to α,β-unsaturated carbonyl compounds

Copper(II) tetrafluoroborate has been found to be a new and highly efficient catalyst for Michael addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions and in H₂O at room temperature. The reactions are very fast and are completed in 2 min to 1 h affording high yields. The rate of thiol addition was dependent on the steric hindrance at the β-carbon of the α,β-unsaturated carbonyl substrate. In the case of chalcones, the reactions are best carried out in MeOH as solvent.     

A facile synthesis of 1,7-dicarbonyl compounds via three-component Michael addition reactions

A convenient one-pot synthesis of 1,7-dicarbonyl compounds has been accomplished by a three-component Michael addition reaction of nitromethane with two unsymmetric α,β-unsaturated carbonyl compounds in the presence of a base.     

Conjugate addition of pyrroles to α,β-unsaturated ketones using copper bromide as a catalyst

Copper bromide was used as a catalyst for the addition of pyrroles to enones. When both the reactants were used in equimolar amounts, mono and dialkylated products were obtained. However, the use of excess enone furnished only dialkylated products. Thus, copper bromide was shown to be an efficient catalyst for the dialkylation of pyrroles.     

Titanocene(III) chloride mediated radical-induced one-pot synthesis of α-methylene-γ-butyrolactones

A simple and efficient methodology has been developed for the one-pot preparation of α-methylene-γ-butyrolactones by free-radical induced Barbier-type reaction of methyl 2-(bromomethyl)acrylate and aldehydes followed by in situ lactonization. The radical initiator titanocene(III) chloride (Cp₂TiCl) was easily generated in situ from commercially available Cp₂TiCl₂ and activated zinc dust in THF. Ketones remained unaffected under the reaction conditions.     

An efficient and improved synthesis of 1,5-diketones: versatile conjugate addition of nucleophiles to α,β-unsaturated enones and alkynones

Several 1,5-diketones have been prepared in good to excellent yields by versatile conjugate addition of nucleophiles such as cyclic or acyclic ketones, amines and thiols to α,β-unsaturated enones and alkynones, in the presence of catalytic amounts of 10% aq NaOH, TBAI and DMSO at ambient temperature. The choice of solvent and phase-transfer catalyst played a critical role in improving the reaction rate and yields of the products.     

AlCl3 as a powerful catalyst for the one-pot preparation of 1,1,3-triheteroaryl compounds

A general and efficient procedure for the synthesis of 1,1,3-triheteroaryl compounds in good to excellent yield at room temperature is developed. The reaction proceeds via mixed Michael and Friedel-Crafts reactions of α,β-enals or α,β-enones and indoles, 2-methylfuran or 2-methylthiophene in the presence of a catalytic amount of AlCl₃.     

Iodine catalyzed conjugate addition of mercaptans to α,β-unsaturated carboxylic acids under solvent-free condition

We have described herein molecular iodine catalyzed Michael addition of thiol to α,β-unsaturated carboxylic acids. This environmentally benign catalytic system (iodine) used under mild and solvent-free conditions to achieve the corresponding adducts in excellent yield.     

Titanocene (III) chloride mediated radical induced synthesis of (−)-methylenolactocin and (−)-protolichesterinic acid

Enantioselective synthesis of two anti-tumor antibiotics, (−)-methylenolactocin and (−)-protolichesterinic acid, has been achieved through titanocene(III) chloride mediated radical cyclization reaction starting from commercially available d-mannitol. Titanocene(III) chloride (Cp₂TiCl) was prepared in situ from commercially available titanocene dichloride (Cp₂TiCl₂) and zinc dust in THF.     

Direct Michael addition to electron-deficient alkenes using diorganyl dichalcogenides (Te/S) and NaBH4/PEG-400

Nucleophilic species of tellurium and sulfur were generated in situ from the reaction of the respective diorganyl dichalcogenides with NaBH₄ in PEG-400 as solvent and selectively added to electron-deficient alkenes. Chalcogenolate anions were directly added at mild conditions by this simple procedure and in all cases furnished the respective Michael adducts in short reaction times and good yields.     

ZrOCl2·8H2O on montmorillonite K10 accelerated conjugate addition of amines to α,β-unsaturated alkenes under solvent-free conditions

At room temperature, ZrOCl₂·8H₂O on montmorillonite K10 efficiently catalyzes conjugate addition of amines to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, nitriles and amides under solvent-free conditions. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency.     

Eco-friendly polyethylene glycol promoted Michael addition reactions of α,β-unsaturated carbonyl compounds

Intra- and inter-nucleophilic addition reactions of different α,β-unsaturated carbonyl compounds were found to be highly effective without any additives in PEG-400 as a recyclable reaction medium under neutral conditions.     

Zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones in the presence of a catalytic amount of mercury(II) chloride

The zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones gives functionalized cyclopentanols in good yield in the presence of a catalytic amount of mercury(II) chloride in N,N-dimethylformamide as solvent at room temperature. The reaction is regio- and stereo-selective producing 3,4-trans-diarylcyclopentanols selectively.     

Palladium catalyzed mild reduction of α,β-unsaturated compounds by triethylsilane

The palladium(II) chloride/triethylsilane system has been successfully applied for the selective hydrogenation of the carbon-carbon double bond of α,β-unsaturated ketones to yield the corresponding saturated carbonyl compounds. The reaction takes place under mild conditions and affords high yields.     

Microwave-assisted InCl3-catalyzed Meyer-Schuster rearrangement of propargylic aryl carbinols in aqueous media: a green approach to α,β-unsaturated carbonyl compounds

A novel, efficient, simple and environmentally benign protocol for the Meyer-Schuster isomerization of propargylic aryl carbinols into α,β-unsaturated carbonyl compounds has been developed using catalytic amounts of InCl₃, pure water as the solvent, and microwave irradiation as the heating source.     

Vanadium(III) chloride as an effective catalyst for the Pechmann reaction

Good yields of substituted coumarins were obtained by a synthetic method involving the Pechmann reaction using vanadium(III)chloride (VCl₃) reagent to effect this condensation under solvent-free conditions. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 197–200, February, 2006.     

Titanocene(III) mediated radical cyclization of α-bromo carbonyl compounds: synthesis of tri-substituted tetrahydrofurans

A novel and efficient methodology has been developed for the construction of synthetically important tri-substituted tetrahydrofuran derivatives from bromo-alkenes and bromo-alkynes by radical cyclization reactions using the radical initiator Cp₂TiCl, generated in situ from commercially available titanocene dichloride and Zn dust in tetrahydrofuran under argon.