A metal-free strategy to construct fluoroalkyl-olefin linkages using fluoroalkanes.

We present a metal-free strategy to access fluoroalkyl-olefin linkages from fluoroalkane precursors and vinyl-pinacol boronic ester (BPin) reagents. This reaction sequence is templated by the boron reagent, which induces C-C bond formation upon oxidation. We developed this strategy into a one-pot synthetic protocol using RCF2H precursors directly with vinyl-BPin reagents in the presence of a Brønsted base, which tolerated oxygen- and nitrogen-containing heterocycles, and aryl halogens. We also found that HCF3 (HCF-23; a byproduct of the Teflon industry) and CH2F2 (HCF-32; a low-cost refrigerant) are amenable to this protocol, representing distinct strategies to generate RCF2H and RCF3 molecules. Finally, we demonstrate that the vinyldifluoromethylene products can be readily derivatized, representing an avenue for late-stage modification after installing the fluoroalkyl unit.

Synthesis of N-methylated amines from acyl azides using methanol.

The transformation of acyl azide derivatives into N-methylamines was developed using methanol as the C1 source via the one-pot Curtius rearrangement and borrowing hydrogen methodology. Following this protocol, various functionalised N-methylated amines were synthesized using the (NNN)Ru(ii) complex from carboxylic acids via an acyl azide intermediate. Several kinetic studies and DFT calculations were carried out to support the mechanism and also to determine the role of the Ru(ii) complex and base in this transformation.

Tandem transformations and multicomponent reactions utilizing alcohols following dehydrogenation strategy.

The construction of new C-C, C-N and C-O bonds by replacing hazardous and waste generating chemicals with alcohols as the greener and sustainable reagents is one of the emerging areas of research. In consequence, the borrowing hydrogen and acceptorless dehydrogenative coupling principles have received significant momentum to synthesize various alkylated molecules and N-heterocycles. In the tandem transformations and multi-component reactions, simple substrates are directly converted to new functionalities or complex molecular systems using a single reaction set-up. In this review, the progress of tandem transformation of nitro, nitrile and azide functionalities as well as multi-component reactions utilizing alcohols is summarised. These transformations lead to the atom-economical synthesis of a wide range of alkylated imines, amines, amides and N-heterocycles such as pyrrole, pyridine, pyrimidine, quinoxaline, etc.

Utilization of MeOH as a C1 Building Block in Tandem Three-Component Coupling Reaction.

Ru(II) catalyzed tandem synthesis of α-branched methylated ketones via multicomponent reactions following the hydrogen borrowing process is described. This nonphosphine-based air and moisture stable catalyst efficiently produced various methylated ketones using methanol as a methylating agent. This system was found to be highly effective in three-component coupling between methanol, primary alcohols, and methyl ketones. A proposed catalytic cycle for the α-methylation is supported by DFT calculations as well as kinetic experiments.

Tandem Transformation of Nitro Compounds into N-Methylated Amines: Greener Strategy for the Utilization of Methanol as a Methylating Agent.

A simple air- and moisture-stable, highly efficient ruthenium NNN pincer complex is reported for the first time to catalyze the tandem transformation of various aromatic and aliphatic nitro compounds into the corresponding N-methylated amines in up to 98 % yield by using methanol as a green methylating agent. Gram-scale reactions of challenging nitro substrates demonstrated the practical application aspects of this catalytic system. Importantly, the N-methylamine moiety could be smoothly introduced to various complex molecular structures without using any expensive palladium/phosphine/amine-based cross-coupling reactions.

Bifunctional Ru(ii) complex catalysed carbon-carbon bond formation: an eco-friendly hydrogen borrowing strategy.

The atom economical borrowing hydrogen methodology enables the use of alcohols as alkylating agents for selective C-C bond formation. A bifunctional 2-(2-pyridyl-2-ol)-1,10-phenanthroline (phenpy-OH) based Ru(ii) complex (2) was found to be a highly efficient catalyst for the one-pot ß-alkylation of secondary alcohols with primary alcohols and double alkylation of cyclopentanol with different primary alcohols. Exploiting the metal-ligand cooperativity in complex 2, several aromatic, aliphatic and heteroatom substituted alcohols were selectively cross-coupled in high yields using significantly low catalyst loading (0.1 mol%). An outer-sphere mechanism is proposed for this system as exogenous PPh3 has no significant effect on the rate of the reaction. Notably, this is a rare one-pot strategy for ß-alkylation of secondary alcohols using a bifunctional Ru(ii)-complex. Moreover, this atom-economical methodology displayed the highest cumulative turn over frequency (TOF) among all the reported transition metal complexes in cross coupling of alcohols.

Bifunctional RuII -Complex-Catalysed Tandem C-C Bond Formation: Efficient and Atom Economical Strategy for the Utilisation of Alcohols as Alkylating Agents.

Catalytic activities of a series of functional bipyridine-based RuII complexes in ß-alkylation of secondary alcohols using primary alcohols were investigated. Bifunctional RuII complex (3 a) bearing 6,6'-dihydroxy-2,2'-bipyridine (6DHBP) ligand exhibited the highest catalytic activity for this reaction. Using significantly lower catalyst loading (0.1 mol %) dehydrogenative carbon-carbon bond formation between numerous aromatic, aliphatic and heteroatom substituted alcohols were achieved with high selectivity. Notably, for the synthesis of ß-alkylated secondary alcohols this protocol is a rare one-pot strategy using a metal-ligand cooperative RuII system. Remarkably, complex 3 a demonstrated the highest reactivity compared to all the reported transition metal complexes in this reaction.

Optimum bifunctionality in a 2-(2-pyridyl-2-ol)-1,10-phenanthroline based ruthenium complex for transfer hydrogenation of ketones and nitriles: impact of the number of 2-hydroxypyridine fragments.

Considerable differences in reactivity and selectivity for 2-hydroxypyridine (2-HP) derived ruthenium complexes in transfer hydrogenation are described. Bifunctional Ru(ii)-(phenpy-OH) [phenpy-OH: 2-(2-pyridyl-2-ol)-1,10-phenanthroline] complex () exhibited excellent catalytic activity in transfer hydrogenation (TH) of ketones and nitriles. Notably, in comparison with all the reported 2-hydroxypyridine (2-HP) derived ruthenium complexes in transfer hydrogenation, complex displayed significantly higher activity. Additionally, exploiting the metal-ligand cooperativity in complex , chemoselective TH of ketones was achieved and sterically demanding ketones were readily reduced. An outer-sphere mechanism is proposed for this system as exogenous PPh3 has no significant effect on the rate of this reaction. This is a rare example of a highly active bifunctional Ru(ii) catalyst bearing only one 2-HP unit.

Interfacial magnetism and exchange coupling in BiFeO3-CuO nanocomposite.

Ferromagnetic BiFeO3 nanocrystals of average size 9 nm were used to form a composite with antiferromagnetic CuO nanosheets, with the composition (x)BiFeO3/(100-x)CuO, x = 0, 20, 40, 50, 60, 80 and 100. The dispersion of BiFeO3 nanocrystals into the CuO matrix was confirmed by x-ray diffraction and transmission electron microscopy. The ferromagnetic ordering as observed in pure BiFeO3 occurs mainly due to the reduction in the particle size as compared to the wavelength (62 nm) of the spiral modulated spin structure of the bulk BiFeO3. Surface spin disorder of BiFeO3 nanocrystals gives rise to an exponential behavior of magnetization with temperature. Strong magnetic exchange coupling between the BiFeO3 nanocrystal and the CuO matrix induces an interfacial superparamagnetic phase with a blocking temperature of about 80 K. Zero field and field cooled magnetizations are analyzed by a ferromagnetic core and disordered spin shell model. The temperature dependence of the calculated saturation magnetization exhibits three magnetic contributions in three temperature regimes. The BiFeO3/CuO nanocomposites reveal an exchange bias effect below 170 K. The maximum exchange bias field HEB is 1841 Oe for x = 50 at 5 K under field cooling of 50 kOe. The exchange bias coupling results in an increase of coercivity of 1934 Oe at 5 K. Blocked spins within an interfacial region give rise to a remarkable exchange bias effect in the nanocomposite due to strong magnetic exchange coupling between the BiFeO3 nanocrystals and the CuO nanosheets.

Effect of oleic acid ligand on photophysical, photoconductive and magnetic properties of monodisperse SnO2 quantum dots.

Oleic acid capped monodisperse SnO(2) quantum dots (QDs) of size 2.7 nm were synthesized by thermal decomposition and oxidation of Sn(II)(oleate) complex in high boiling nonpolar solvent octadecene using oleic acid as a capping agent and N-methylmorpholine N-oxide as an oxidizing agent. FTIR, DSC and TGA were employed to understand the growth of the oleic acid capped SnO(2) QDs through the decomposition of metal fatty acid complex. The surface defect-related luminescence properties of the QDs were demonstrated using steady-state and time-resolved spectroscopy. The oleic acid capping on the QD surface modifies the electronic structure of SnO(2) and generates blue emission. Moreover the surface capping on the QDs diminishes the photocatalytic activity of bare SnO(2) QDs due to absence of surface oxygen and adsorbed hydroxyl group on the surface of the capped QDs. The capping by the long chain ligand oleic acid makes the SnO(2) QDs less conducting. Ligand exchange of the long chain oleic acid (2.5 nm) by the short chain n-butylamine (0.6 nm) increases the current density of SnO(2) around 43 times due to the reduction of the interparticle distance. Ferromagnetic behaviour of oleic acid capped QDs may be ascribed to the defects in the host due to the alteration of the electronic structure owing to the capping.