CsF–Al<SUB>2</SUB>O<SUB>3</SUB> mediated rapid condensation of phenols with aryl halides: comparative study of conventional heating vs. microwave irradiation

Biaryl ethers and thio ethers are formed in high yields by the condensation of phenols and thiophenols with electron-deficient aryl halides using CsF supported on Al2O3 under microwave irradiation in solvent-free conditions

Metal triflates catalyzed efficient synthesis of 3,4-dihydro-2H-1-benzopyrans

Ytterbium triflate efficiently catalyzes an unusual cyclization of o-hydroxybenzaldehydes with 2,3-dihydrofuran and 3,4-dihydro-2H-pyran in the presence of trimethyl orthoformate at ambient temperature to afford a new class of compounds, furo- and pyrano[2,3-b]benzopyrans in excellent yields with high diastereoselectivity. Also, o-hydroxybenzaldehydes reacted smoothly with acetophenones in the presence of a catalytic amount of scandium triflate under similar reaction conditions to give the corresponding 2,4-dialkoxy-2-aryl-3,4-dihydro-2H-1-benzopyrans in high yields

Ru(II)-Catalyzed Oxidative Functionalization of Arylhydrazine-1,2-dicarboxylates with Internal Alkynes for the Synthesis of Enecarbamates

A novel method has been developed for the synthesis of highly substituted enecarbamates and trisubstituted alkenes from arylhydrazine-1,2-dicarboxylates and 1,2-disubstituted alkynes through a sequential C–C and C–N bond formation. It is entirely a new strategy to produce enecarbamates in a highly regio- and stereoselective manner

Iron (III) chloride as mild and efficient reagent for the α-thiocyanation of ketones: an expedient synthesis of α-oxo thiocyanates

A simple and efficient method for the α-thiocyanation of ketones has been developed; anhydrous iron(III) chloride is used under mild conditions to produce α-oxo thiocyanates in good to high yields and with high selectivity. The use of inexpensive and readily available iron(III) chloride makes this procedure simple, convenient, and practical

Highly stereoselective synthesis of 2,3- unsaturated thioglycopyranosides employing molecular iodine

Molecular iodine has been utilized for the first time for the thioglycosidation of D-glycals with various thiols to afford the corresponding 2,3-unsaturated thioglycosides in high yields. In the case of tri-O-acetyl-D-glucal, the α-anomer was obtained exclusively. The use of readily available iodine makes this method quite simple, more convenient, and practical

Dy(OTf)<SUB>3</SUB>-immobilized in ionic liquids: a novel and recyclable reaction media for the synthesis of 2,3-unsaturated glycopyranosides

D-Glycals react smoothly with a variety of alcohols, phenols and hydroxy α-amino acids in the presence of 5 mol% dysprosium triflate immobilized in 1-butyl-3-methylimidazolium hexafluorophosphate under mild reaction conditions to afford the corresponding 2,3-unsaturated glycopyranosides in excellent yields with high α-selectivity. The catalyst immobilized in ionic liquids was recycled in subsequent reactions without any apparent loss of activity

Substrate-Directed C-H Functionalization of 2-Aryl Pyridines by Transition Metal Complexes

International audienceTransition metal mediated C-H activation is a powerful synthetic tool for the total synthesis of complex natural products and biologically active molecules. The strategy involves mainly C-H activation, nucleophilic addition and regeneration of the catalyst. It proceeds through a C-H bond cleavage by ligand coordination to transition metal. Transition metals like Pd, Rh, Ru, Co, and Ir are the most often used catalysts, which form a complex with 2-aryl pyridine and facilitates the functionalization of various C-H bonds to generate diverse C-C and C-X bonds under typically mild reaction conditions with low catalyst loading. In particular, the chelation-assisted cleavage of C-H bonds at ortho-position of the pyridine directing group has been recognized as one of the most powerful strategies for the functionalization of unreactive C-H bonds. Recently, transition metal catalyzed C-H bond activation has received significant interest because it does not require the prefunctionalization of the substrate. Therefore, the metal-catalyzed C-H activation and functionalization is currently considered as atom economy and simplified procedure in comparison with the traditional strategies

Montmorillonite clay-catalyzed stereoselective syntheses of aryl-substituted (E)- and (Z)-allyl iodides and bromides

An efficient and rapid procedure for the synthesis of allyl iodides and bromides from Baylis-Hillman adducts using clay-supported sodium iodide and sodium bromide is described. Improved yields and enhanced rates have been achieved by employing microwave irradiation

InCl<SUB>3</SUB> immobilized in ionic liquids: a novel and recyclable catalytic system for tetrahydropyranylation and furanylation of alcohols

A mild and highly efficient method has been developed for the protection of hydroxyl compounds as tetrahydropyranyl and furanyl ethers using a catalytic amount of indium trichloride immobilized in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid under mild conditions. A wide range of functional and protecting groups such as THP, TBDMS, TBDPS, PMB, MOM ethers, acetonides, olefins and epoxides are compatible with ionic liquids. Monoprotection of diols has also been achieved using this novel procedure