Polymethylhydrosiloxane (PMHS)/trifluoroacetic acid (TFA): a novel system for reductive amination reactions

Rate and Yield Enhancements in Nucleophilic Aromatic Substitution Reactions via Mechanochemistry

A variety of nucleophilic aromatic substitution reactions were carried out mechanochemically to great advantage. On average, reactions rates were nine-times faster. The corresponding kinetic studies presented provide the clearest head-to-head kinetic comparisons between mechanochemical and conventional systems at identical temperatures. Attempts are provided at classifying the kinetics of one example. Removal of polar, protic solvents from these reactions presents environmental benefits to a reaction class whose kinetics are heavily dependent on such solvents.

Scope and Limitations of Reductive Amination Catalyzed by Half-Sandwich Iridium Complexes Under Mild Reaction Conditions

The conversion of aldehydes and ketones to 1° amines could be promoted by half-sandwich iridium complexes using ammonium formate as both the nitrogen and hydride source. To optimize this method for green chemical synthesis, we tested various carbonyl substrates in common polar solvents at physiological temperature (37 °C) and ambient pressure. We found that in methanol, excellent selectivity for the amine over alcohol/amide products could be achieved for a broad assortment of carbonyl-containing compounds. In aqueous media, selective reduction of carbonyls to 1° amines was achieved in the absence of acids. Unfortunately, at Ir catalyst concentrations of <1 mM in water, reductive amination efficiency dropped significantly, which suggest that this catalytic methodology might be not suitable for aqueous applications where very low catalyst concentration is required (e.g., inside living cells).

A novel route to unsymmetrical disubstituted ureas and thioureas by HMPA catalyzed reductive alkylation with trichlorosilane

A HMPA catalyzed reductive alkylation of ureas and thioureas with trichlorosilane under mild reaction conditions has been developed.

Phosphorous(v) Lewis acids: water/base tolerant P3-trimethylated trications

The water/base intolerance of the previously reported electrophilic phosphonium cations has been overcome by replacing the labile electron-withdrawing groups generally attached to phosphorus (e.g. -F, -OAr, -CF3) with methyl groups. Tri-phosphorus(v) tricationic species, accessible in one-pot from commercially available materials, are air and water/base tolerant, yet are sufficiently Lewis acidic for catalysis.

A novel synthetic approach to poly(hydrosiloxane)s via hydrolytic oxidation of primary organosilanes with a AuNPs-stabilized Pickering interfacial catalyst

A simple and versatile approach based on AuNPs-stabilized Pickering catalyst in water–chloroform biphasic medium has been developed for the synthesis of poly(alkyl/arylhydrosiloxane)s.

Palladium nanoparticles anchored on polymer vesicles as Pickering interfacial catalysts for hydrolytic oxidation of organosilanes

The self-assembly of functional polymer vesicles embedded with PdNPs at water–chloroform interfaces provides a novel catalytic route for the synthesis of poly(hydrosiloxane)s, H₂RSi[OSiRH]_nOSiRH₂.

Reductive amination catalyzed by iridium complexes using carbon monoxide as a reducing agent

N-benzyl, dioxalane, halo-, cyclopropanes tolerates.

Main group catalysed reduction of unsaturated bonds

This Perspective article reviews the recent developments in reduction reactions catalysed by main-group element compounds.

Reductive amination using a combination of CaH2 and noble metal

Amines were prepared by a reductive amination reaction in the presence of calcium hydride and Pt/C.

Reductive Amination of Acetals by Anilines in the Presence of Triethylsilane and Iodine

A mild and efficient method for N-alkylation of aromatic amines with various acetals such as aryl, alkyl, cyclic and acyclic acetals was developed. A number of aromatic amines bearing electron-donating or electron-withdrawing substituents were directly alkylated by acetals with excellent yields. The method uses a catalytic amount of I2 and triethylsilane as the hydride source without a metal present. Monoalkylation with excellent chemoselectivity was observed.

Epoxide group relationship with cytotoxicity in withanolide derivatives from Withania somnifera

Withania somnifera is one of the highly reputed medicinal plants of India. Its steroidal constituents exist in the form of two major substitution patterns, viz. withaferin A (1) and withanone (5). Withaferin A with oxidation at carbons 4, 5, and 6 is considered as an active type, especially as anticancer, whereas the withanones with oxidation at carbons 5, 6, and 7 rarely show any activity. We prepared a series of derivatives with modifications at carbons 5, 6, and 7 in ring B of these withanolides to study the role of the epoxide group towards the cytotoxic property of these bioactive steroids. We have converted withanolides into the respective thiiranes, amino alcohols and alcohols by selective reactions at the epoxide ring and were evaluated for in vitro anticancer activity against four cancer cell lines to study the structure activity relationships. The transformations of the epoxide group in withanolides of the withaferin A type showed moderate reduction in their cytotoxicity whereas the almost inactive withanones have shown some improvements in their alcohol derivatives.

Stereoselective direct reductive amination of ketones with electron-deficient amines using Re2O7/NaPF6 catalyst

The first example of direct reductive amination (DRA) of ketones with electron-deficient amines (EDA) such as Cbz-, Boc-, EtOCO-, Fmoc-, Bz-, ArSO2-, etc. protected amines have been achieved using catalytic Re2O7/NaPF6. Excellent chemoselectivities as well as diastereoselectivity (for 2-alkyl cyclohexanones) were obtained.