Nanocrystallite Zeolite BEA for Regioselective and Continuous Acetyl Functionalization of Anisole Using Acetic Anhydride: Catalyst Deactivation Studies.

Ultrasonic pretreatment of gel composition followed by hydrothermal synthesis produces the nanocrystallite zeolite beta (ZB) with crystal sizes of 10.3, 22.6, and 9.1 nm for ZB-1, ZB-2, and ZB-3, respectively. The effect of ultrasonic pretreatment and the (SiO2/Al2O3) ratio of gel composition on physical, textural properties, and also on the catalytic activity of ZB catalysts with increasing time on stream (TOS) was investigated. The specific surface area and mesopore volume for ZB-1, ZB-2, and ZB-3 are 438, 380, and 429 m2/g and 0.17, 0.05, and 0.14 cm3/g, respectively. The activity studies of ZB-1 and ZB-3 catalysts were confirmed that the anisole conversion initially increased with TOS until it attained the maximum value and then started decreasing further with TOS due to the deactivation of the catalyst caused by the strong interaction of the product with the acidic sites in the mesopore region. However, in the case of ZB-2, the anisole conversion (>45%) was sustained for a longer TOS due to its smaller particle size, low mesopore volume, and more acidic sites in the micropore volume that are inclusively made for retardation in the catlytic deactivation rate. The CHNS and TGA analysis of the spent catalysts confirm that ZB-1 and ZB-3 catalysts are susceptible for a significant coke formation attributed due to strong product retention in their large mesopore volume, which lead to the catalytic deactivation.

Correction: A multi-component reaction for the synthesis of pyrido [1,2-b] isoquinoline derivatives via the [3 + 2] cycloaddition reaction between alkynes and in situ generated isoquinolinium ylides.

Correction for 'A multi-component reaction for the synthesis of pyrido [1,2-b] isoquinoline derivatives via the [3 + 2] cycloaddition reaction between alkynes and in situ generated isoquinolinium ylides' by Sundar S. Shinde et al., Org. Biomol. Chem., 2019, 17, 4121-4128, DOI: 10.1039/C9OB00560A.

A multi-component reaction for the synthesis of pyrido [1,2-b] isoquinoline derivatives via the [3 + 2] cycloaddition reaction between alkynes and in situ generated isoquinolinium ylides.

An efficient and one-pot tandem procedure for the synthesis of fused ethanopyrido [1,2-b] isoquinoline derivatives from ninhydrin, proline and alkynes has been developed. This strategy exhibits an unprecedented [3 + 2] cycloaddition reaction between alkynes and isoquinolinium ylide (1,3 dipole) generated in situ from proline and ninhydrin. This newly developed methodology features simple operation and is metal free. In this methodology overall three new C-C bonds, two C-N bonds, and three new rings are formed in a single step process.

Correction: Magnetically recoverable Cu0/Fe3O4 catalyzed highly regioselective synthesis of 2,3,4-trisubstituted pyrroles from unactivated terminal alkynes and isocyanides.

Correction for 'Magnetically recoverable Cu0/Fe3O4 catalyzed highly regioselective synthesis of 2,3,4-trisubstituted pyrroles from unactivated terminal alkynes and isocyanides' by Dipak Kumar Tiwari et al., Chem. Commun., 2016, 52, 4675-4678.

Transition-Metal-Free Approach for the Synthesis of 4-Aryl-quinolines from Alkynes and Anilines.

An efficient and transition-metal-free approach for the synthesis of 4-arylquinolines from readily available anilines and alkynes in the presence of K2S2O8 and DMSO has been developed. A variety of alkynes and anilines having a diverse range of substitution patterns can undergo the one-pot cascade process successfully. Effectively, this method uses DMSO as one carbon source, thus providing a highly atom-economical and environmentally benign approach for the synthesis of 4-arylquinolines.

Unprecedented synthesis of 1,2,3-triazolo-cinnolinone via Sonogashira coupling and intramolecular cyclization.

An unprecedented copper mediated one-pot sequential synthesis of 1,2,3-triazolo cinnolinone derivatives from 2-halo-phenyl triazoles and terminal alkynes has been reported. Under the optimized reaction conditions, a broad range of substituted triazoles and alkynes were found to participate in this transformation, thus affording unknown 1,2,3-triazolo cinnolinone derivatives in moderate to excellent yields. This method proceeds through sequential C-C coupling followed by an annulation cascade sequence in the same vessel under atmospheric air as the sole oxidant, thus representing a simple, efficient and atom economical approach for the synthesis of aza-cinnolinones.

Transition-Metal-Free Quinoline Synthesis from Acetophenones and Anthranils via Sequential One-Carbon Homologation/Conjugate Addition/Annulation Cascade.

A transition-metal-free method for the construction of functionalized quinolines from readily available acetophenones and anthranils is reported. This one-pot reaction cascade involves in situ generation of α,ß-unsaturated ketones from the acetophenone via one-carbon homologation by DMSO followed by the aza-Michael addition of anthranils and subsequent annulation. DMSO acted in this reaction not only as solvent but also as one carbon source, thus providing a highly atom-economical and environmentally benign approach for the synthesis of 3-substituted quinolines.

Magnetically recoverable Cu(0)/Fe3O4 catalyzed highly regioselective synthesis of 2,3,4-trisubstituted pyrroles from unactivated terminal alkynes and isocyanides.

An efficient, one pot tandem nano Cu(0)/Fe3O4 catalyzed highly regioselective synthesis of 3-substituted pyrrole-2,4 dicarboxylates from unactivated terminal alkynes and isocyanides has been developed. This strategy exhibits an unprecedented double addition of isocyanides on unactivated terminal alkynes to obtain trisubstituted pyrroles in high yields. Furthermore, the catalyst was magnetically recovered and reused five times without any appreciable loss of activity.

Electronically modified amine substituted alkynols for regio-selective synthesis of dihydrofuran derivatives.

An efficient and simple approach has been developed for the regio-selective synthesis of iodo-substituted dihydrofurans from amine substituted alkynols. The resulting iodo-substituted dihydrofurans have been further diversified by C-C couplings and C-N coupling reactions to afford a diverse range of substituted dihydrofuran derivatives.

Nano-copper catalysed highly regioselective synthesis of 2,4-disubstituted pyrroles from terminal alkynes and isocyanides.

Nano-copper(0) stabilized on alumina prepared from Cu-Al hydrotalcite has been reported for completely regioselective synthesis of 2,4-disubstituted pyrroles from unactivated terminal aromatic/aliphatic alkynes and isocyanides. The reaction is operationally simple, involves ligand-free inexpensive nano-copper, and affords products in high yields.

An expedient approach to pyrrolo[3,2-c]quinolines via regioselective formation of the pyrrole nucleus over indoles.

An efficient approach for the synthesis of pyrrolo[3,2-c]quinolines (the core nucleus of the natural product martinellic acid) from protected 2-alkynylanilines via the regioselective formation of pyrroles followed by Heck and intramolecular Michael addition has been described.

Base-mediated chemo- and stereoselective addition of 5-aminoindole/tryptamine and histamines onto alkynes.

Transition-metal-free chemo- and stereoselective addition of 5-aminoindole (1a), tryptamine (1b), and histamine (1c) to alkynes 2a-s to synthesize the indolyl/imidazolyl enamines 3a-p, 5a-o, and 6a-e using superbasic solutions of alkali-metal hydroxides in DMSO is described. The addition of N-heterocycles onto alkynes takes places chemoselectively without affecting the 1° amino groups (aromatic and aliphatic) of 5-aminoindole, tryptamine, and histamine. The stereochemistry of the products was found to be dependent upon reaction time; an increase in reaction time leads to the formation of a mixture of E/Z isomers and the thermodynamically stable E addition product. The chemoselective addition of N-heterocycle 1a onto alkyne over thiophenol 7 and phenol 8 is supported by control experiments. Competitive experiments showed that 5-aminoindole was more reactive than tryptamine, and histamine was found to be the least reactive. The present methodology provides an efficient chemoselective method to synthesize a variety of (Z)-enamines of 5-aminoindole, tryptamine, and histamine without affecting the 1° amino group. The presence of the free amino group in enamines could be further used for synthetic elaboration, which proved to be highly advantageous for structural and biological activity assessments.

New cyclopalladated benzothiophenes: a catalyst precursor for the Suzuki coupling of deactivated aryl chlorides.

Dimeric benzothiophene-based palladacycles were synthesized from thioanisole-substituted perfluoroalkyl propargyl imines and palladium(II) salts via an intramolecular thiopalladation pathway. The treatment of benzothiophene-based palladacycles with an excess of phosphine ligands in benzene at room temperature selectively afforded trans-bis(phosphine) palladium complexes in good yields. The trans-bis(tricyclohexylphosphine) palladium complex was found to be an active catalyst in the Suzuki coupling of electron rich aryl chlorides. The complex was also employed in the catalytic synthesis of sterically hindered biaryls. The anticancer activity of palladacycles is also discussed.

Trifunctional N,N,O-terdentate amido/pyridyl carboxylate ligated Pd(II) complexes for Heck and Suzuki reactions.

Trifunctional N,N,O-terdentate amido/pyridyl carboxylate Pd(II) complexes were highly active and stable phosphine-free catalysts for Heck and room-temperature Suzuki reactions with high turnover numbers up to ca. 10(4).

N4-tetradentate dicarboxyamidate/dipyridyl palladium complexes as robust catalysts for the Heck reaction of deactivated aryl chlorides.

Structurally well defined and thermally stable Pd(II) complexes, derived from N4-tetradentate dicarboxyamide/dipyridyl ligands, were evaluated as catalysts for the Heck reactions of deactivated aryl chlorides and olefins (see scheme). The concept of using an anionic carboxyamide as an ancillary ligand for palladium demonstrated here provides a new opportunity for the development of phosphine-free transition-metal catalysis.

Synthesis of highly substituted 2-perfluoroalkyl quinolines by electrophilic iodocyclization of perfluoroalkyl propargyl imines/amines.

A series of highly substituted 2-perfluoroalkyl-3-iodoquinolines are prepared by two different methods in good to excellent yields under mild reaction conditions. The first method involves iodocyclization of perfluoroalkyl propargyl imines with I(2)-CAN. The second method involves iodocyclization of perfluoroalkyl propargyl amines using I(2) and ICl. The perfluoroalkyl propargyl amines are prepared in excellent yields via Sonogashira coupling of easily accessible imidoyl iodides with alkynes followed by reduction with NaBH(3)CN. The scope of this methodology is extended by using the resulting 2-perfluoroalkyl-3-iodo quinolines in Suzuki, annulation, dehalogenation and carboxylation reactions. Antimalarial activity of the 2-perfluoroalkyl-3-iodoquinolines is discussed.

An efficient copper-aluminum hydrotalcite catalyst for asymmetric hydrosilylation of ketones at room temperature.

A catalyst system consisting of a copper-aluminum hydrotalcite-chiral diphosphine ligand effects asymmetric hydrosilylation of several ketones, using polymethylhydrosiloxane (PMHS) as the stoichiometric reducing agent at room temperature, with moderate-to-excellent enantioselectivities. The catalyst is recovered by simple centrifugation, and the efficiency of the catalyst remains almost unaltered even after several cycles.

Preparation and structural characterisation of methoxybis(trimethylsilyl)silyl potassium and its condensation product.

Depending on the conditions the reaction of tris(trimethylsilyl)methoxysilane (1) with potassium tert-butoxide either in benzene and in the presence of 18-crown-6 or in THF gives either the crown ether adduct of potassium-methoxybis(trimethylsilyl)silane (2), or 2-methoxytetrakis(trimethylsilyl)disilanyl potassium (3).