Search

Herein, we report an efficient and sustainable manganese‐catalyzed α‐C−H bond alkylation methodology to synthesize branched sulfones via a hydrogen borrowing pathway. The air‐stable and phosphine‐free Mn‐catalyst, (NNN)Mn(II)Cl2 was synthesized by using an earth‐abundant, commercially available, and inexpensive precursor MnCl2.4H2O, and a stable NNN pincer i. e. [N‐((benzimidazole‐2‐yl)methyl)quinoline‐8‐amine] ligand system. Taking benzyl phenyl sulfones as substrates, and benzyl alcohol derivatives as alkylating agents, a range of branched sulfones were synthesized in 40–82 % isolated yields using (NNN)Mn(II)Cl2 complex as the catalyst under open‐air conditions. Control experiments and deuterium incorporation studies have also been conducted to investigate the possible reaction mechanism and to provide evidence for the hydrogen borrowing pathway. [ABSTRACT FROM AUTHOR]

In this study, we propose an alternative metal‐free methodology for the synthesis of Streptindole and its derivatives. This approach employs economically viable and easily handled molecular iodine (I2) as the catalyst in an aqueous medium. The method demonstrates remarkable tolerance towards a diverse array of functional groups. The versatility of the developed protocol is highlighted by its application in the efficient total syntheses of the alkaloid natural products, Streptindole and Arsindoline B accomplished in a single step from indole. Furthermore, the methodology is also useful for the synthesis of pharmaceutically significant compounds, specifically anti‐TMV agents (5 c, 5 d, and 5 e) and an anticancer agent (5 f). Control experiments have been carried out to study the plausible catalytic cycle by finding the key intermediates. The experimental findings support the mechanistic pathway involving halogen bond activation in molecular iodine catalysis. [ABSTRACT FROM AUTHOR]

Herein, we report an efficient methodology for the reduction of esters, carbonates, and anhydrides to alcohols using in situ generated aminodiborane from iodine and ammonia borane. This methodology also finds use for the transformation of esters to iodides by varying the stoichiometry of reagents. The protocol has broad substrate scope for transformation of esters to alcohols and iodides with excellent yields. The method is also useful for synthesizing pharmaceutically and industrially important compounds such as a Cinacalcet precursor, a Streptoindole analogue, and 1,4-pentanediol. Control studies and DFT calculations carried out to study the reduction mechanism of esters using aminodiborane indicate that a dioxaborinamine intermediate is formed during the reaction. [ABSTRACT FROM AUTHOR]

Herein, we report a palladium‐catalyzed 'on‐water' methodology for the synthesis of biaryl and m‐teraryl derivatives of aryl carboxamides by selective mono and bis C−H bond functionalization. 8‐aminoquinoline and 2‐thiomethylaniline were used as directing groups for C−H bond functionalization of aryl carboxamides with various aryl and alkyl iodides using 3.0–4.0 mol% of Pd(OAc)2 as catalyst and water as the solvent resulting in 45–97% isolated yields of the mono and bis C−H bond functionalized products. Using an 8‐aminoquinoline carboxamide core, C−H bond functionalization of indole‐3‐carboxylic acid and a late‐stage functionalization of aspirin molecule have also been carried out. Reactions of benzyl/naphthyl picolinamides with aryl iodides gave 60–96% yield of the arylated products using the picolinamide directing group. Moreover, the insoluble nature of products in an aqueous medium enabled us to explore the reusability of the solvent, i. e. water and the catalyst. Control experiments and structural studies were carried out which confirmed the in situ formation of unique palladacycles during the reaction. Removal of the directing groups has been carried out to convert the functionalized products into amines and fluorenone compounds useful in industrial and pharmaceutical applications. [ABSTRACT FROM AUTHOR]

Herein, we report a new air‐stable phosphine‐free 8‐AQ (8‐aminoquinoline) based Mn(I) carbonyl complex as the catalyst for the C(α)‐alkylation of oxindoles with alcohols. The Mn complex [(8‐AQ)Mn(CO)3Br] works effectively as a catalyst for the α‐alkylation of oxindoles by both secondary as well as primary alcohols. The procedure has been used for the synthesis of pharmaceutically important recently developed oxindoles such as 3‐(4‐methoxybenzyl)indolin‐2‐one, 3‐(4‐(dimethylamino)benzyl)indolin‐2‐one, 3‐(4‐(dimethylamino)phenyl)‐5‐fluoroindolin‐2‐one and 3‐(benzo[d][1,3]dioxol‐5‐ylmethyl)indolin‐2‐one, which are found to be effective in preventing specific types of cell death in neurodegenerative disorders. Control experiments have been carried out to investigate the reaction mechanism and the crucial role of metal‐ligand cooperation via ‐NH2 moiety during catalysis. [ABSTRACT FROM AUTHOR]

New water soluble neutral and cationic palladium complexes were synthesized using 8‐aminoquinoline (8‐AQ) and 2‐methyl 8‐aminoquinoline (2‐Me 8‐AQ) ligands and their catalytic properties were evaluated. The neutral trimeric complexes having a Pd3N3 core were found to form when Pd(OAc)2 was reacted with 8‐AQ or 2‐Me 8‐AQ irrespective of the stoichiometry between the 2 reagents. Controlled addition of triflic acid to the neutral trimeric complex resulted in the formation of a trimeric cationic palladium complex as well as a monomeric cationic complex. A cationic palladium complex having two units of 2‐Me‐8AQ ligand was also synthesized from the cationic monomeric complex. Crystal structures of the new palladium complexes are reported in this study. The water‐soluble neutral palladium complex showed catalytic activity for the oxidation of benzyl alcohols to benzaldehydes, while the cationic palladium complexes were found to be efficient catalysts for the oxidation of styrenes to methyl ketones. [ABSTRACT FROM AUTHOR]

A water‐soluble bifunctional, bistate ruthenium catalyst has been developed using the 8‐aminoquinoline ligand which responds to an acid‐base stimuli and is catalytically active for two complementary reactions. The "Ru‐amino state" is highly active for catalytic transfer hydrogenation of various aldehydes using formic acid as the hydrogen source resulting in a range of primary alcohols. On the other hand, the "Ru‐amido state" is active for the acceptorless dehydrogenation of alcohols to yield carboxylate salts or ketones. The reactions can be carried out in air without an inert atmosphere and the products can be purified by simple extraction without the use of any chromatographic techniques. A range of functional groups which include electron‐rich and deficient (hetero)arenes and alkenes, alkynes, halides, esters, cyano, and nitro groups, are all well tolerated, indicating excellent chemoselectivity for transfer hydrogenation. [ABSTRACT FROM AUTHOR]

γ‐Valerolactone (GVL), an industrially important compound and green‐solvent was synthesized using a metal‐free method by I2/Et3SiH directly from levulinic acid at room temperature in good yield. Different types of keto‐acids were also subjected to this methodology to synthesize the corresponding lactones. A 2‐gram scale reaction was successfully carried out in good yield. Control experiments indicated that in situ generated Et3SiI is the active catalyst for this reaction. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of two novel fluorophosphazene derived from cobaltocyclopentadienylmetallacycles is reported and a hitherto unknown synthetic route for making aryl bridged fluorinated cyclophosphazenes by the reaction of the metallacycles with substituted acetylenes is provided. These cobaltametallocycles are possible precursors for making novel acetylene-trimerized aryl compounds as well as [[eta].sup.5]-Cp]Co[[[eta].sup.4]-R4C4] metallocenes.

The reinvestigation of the molecular structure of the parent molecule N(sub 4)P(sub 4)F(sub 8) by using x-ray diffraction, gas electron diffraction and differential scanning calorimetry is described. The results from each of these measurements support a nonplanar eight-membered ring for N(sub 4)P(sub 4)F(sub 8) that is puckered and that undergoes a phase transition at -74 degrees C.

Syntheses of 1,3-ansa, spiro and bridged derivatives of tetrameric fluorophosphazene are discussed. In the presence of CsF, the ansa and bridged derivatives are converted to the spiro compound, indicating the higher thermodynamic stability of the latter.

Research demonstrates for the first time the synthesis and structural aspects of exo and endo isomers of ansa-substituted fluorophosphazenes. Results show that the ansa to spiro transformation occurs at temperatures in the range from -20 to +33 C.

A study was conducted to determine the dealkylation reactions of trialkylamines with 1,3,5,-trichloro-1,2,4,6-cyclothiatriazine (CICN)2(CISN). Findings show the emergence of a facial cleavage of a C-N bond of the tertiary amine and the regiospecific substitution of the dialkylamino group on the carbon atoms of the heterocyle. It was also observed that the (CISN)2(CISN) releases thiatriazine with dimethylamino groups substituted on the ring carbon atoms as a response to its interaction with tetramethylmethylenediamine.

Acyclic tertiary amines such as triethylamine and tri-n-propylamine were used as HCl scavengers in nucleophilic substitution reactions of cyclic chlorocarbaphosphazenes. The acyclic tertiary amines undergo facile C-N bond cleavage and induced regiospecific substitutions in the dialkylamino groups on the ring carbon atoms of carbaphosphazene. Reactions of the lithium salts of fluoro diols resulted in selectively substituted C-Cl bond with silylamines or sodium phenoxide/thiophenoxide.