CuII-Catalyzed cis-Selective Synthesis of Ketoepoxides from Phenacyl Bromides and Water.

A verity of α,ß-ketoepoxides was synthesized using a CuII-catalyzed oxidative C-C/O-C coupled cyclization strategy with high yield and cis-selectivity. Water is used as the source of oxygen and phenacyl bromide as the carbon in the valuable epoxides. The self-coupling method was extended to cross-coupling between phenacyl bromides with benzyl bromides. A high cis-diastereoselectivity was observed in all the synthesized ketoepoxides. Control experiments and density functional theory (DFT) study were performed to understand the CuII-CuI transition mechanism.

Water-based efficient alkyne transformation towards α-acetoxy/imido-ketones via oxidative coupling reactions using an alkylamine catalyst.

A novel approach is unveiled for the expedited synthesis of valuable α-substituted ketones, utilising aliphatic amine catalysis to drive the oxidative C-O/C-N coupling reaction between alkynes and an appropriate nucleophile. This one-pot synthesis employs hypervalent iodine as both the oxidant and coupling agent. A fast, metal-free, and environmentally benign method is developed for synthesising α-acetoxyketones and α-imidoketones in an aqueous medium. To demonstrate the potential for larger-scale production, a gram-scale reaction is conducted. Moreover, the newly developed methodology has successfully enabled the direct synthesis of cathinone, a psychoactive drug. Overall, this work holds significant promise for the efficient and sustainable synthesis of α-substituted ketones and the potential development of novel biologically active compounds.

Cu(I)-catalysed cross-coupling reaction of in situ generated azomethine ylides towards easy construction of fused N-heterocycles.

In this study, we have devised a new method for synthesizing highly valuable 5,6,7,8a-tetrahydropyrrolo[2,1-b]thiazoles using a decarboxylative C-N coupling reaction between phenyl glyoxal and proline or its analogue, which is catalyzed by CuI in the presence of K2CO3. This reaction is followed by a regiospecific C-C and C-S coupling cyclization with dialkyl trithiocarbonate. Furthermore, we have demonstrated that this cross-coupling method can also be extended to imines, leading to the formation of fused symmetrical and unsymmetrical 6,7-dihydro-5H-pyrrolo[1,2-a]imidazoles. This finding greatly expands the scope and versatility of the synthetic approach. Therefore, this work represents a significant contribution to the field of organic synthesis, providing a novel and efficient method for the preparation of fused N-heterocyclic compounds that could have useful applications in areas such as material science and pharmaceuticals.

CeCl3·7H2O catalyzed C-C and C-N bond-forming cascade cyclization with subsequent side-chain functionalization and rearrangement: a domino approach to pentasubstituted pyrrole analogues.

CeCl(3)·7H(2)O is found as an efficient catalyst for new intermolecular domino reactions of three-, four- and seven-component assemblies of common precursors under benign reaction conditions. Generation of enaminioesters from ß-keto esters and primary amines, activation of their allylic sp(3) C-H, vinylic sp(2) C-H and N-H bonds, multi C-C and C-N bond-forming cascade cyclization with 1,2-diketones and subsequent side-chain alkylation have been developed to construct functionalized pentasubstituted pyrroles and their chiral analogues. The scope of the domino reaction is successfully explored toward synthesis of highly aryl-substituted pyrroles, pentasubstituted pyrroles bearing C2-olefinic side-chain and spiro-2-pyrrolinones and their chiral analogues via unusual side-chain amination, elimination and ring contraction. The new domino reaction is operationally simple, robust, substrate specific, selective and high yielding.

Selective amidation by a photocatalyzed umpolung reaction.

A metal-catalyzed organic transformation merged with another organophotocatalyst has been developed under mild conditions for production of α-ketoamides. CuI-catalyzed highly selective and rapid COCH2-amidation in the presence of electrophilic Cα[double bond, length as m-dash]O bonds, which is synchronized by an eosin Y (EY)-photocatalyst, furnishes a wide range of labile α-ketoamides, unsymmetrical oxalamides and chiral analogues on the treatment of 1,3-dicarbonyls with amines, PhIO and LED light at room temperature. The current strategy opens up a new avenue to making photocatalysis a common synthetic tool for large-scale production in academia and industry.

Photocatalytic Generation of Nitrenes for Rapid Diaziridination.

A blue LED, an organic photocatalyst (rose bengal), and the Lewis acid like oxidant PhI(OAc)2 were utilized to generate nitrene intermediates through reactions of 1,2-diols and aliphatic amines under mild reaction conditions. A versatile and rapid diaziridination strategy was established to construct functionalized 1,2-disubstituted diaziridines, diaziridines with chiral substituents, and 1,2,3-trisubstituted analogues with excellent reaction rates, yields, and stereoselectivities. Control and labeling experiments to elucidate the mechanism of this elegant metal-free photocatalyzed cyclization reaction were performed.

CuBr-ZnI2 Combo-Catalysis for Mild CuI-CuIII Switching and sp2 C-H Activated Rapid Cyclization to Quinolines and Their Sugar-Based Chiral Analogues: A UV-Vis and XPS Study.

An unprecedented CuBr-ZnI2 combo-catalyzed mild Cu1-CuIII switching activation of sp2 C-H of highly electron-rich arenes is reported. Anilines, aldehydes, and terminal alkynes were rapidly coupled together at ambient temperature to construct a ubiquitous quinoline framework through cyclization of the C≡C bond. This smart solvent-free strategy was exploited for the direct synthesis of valuable 4-substituted, 2,4-disubstituted, and thermally labile sugar-based chiral quinolines in good yields. In contrast to the frequently used imine-alkyne cyclization reaction, this uncommonly mild CuI-CuIII combo-catalysis for a rapid three-component cyclization is expected to proceed through the formation of a flexible propargyl amine intermediate, which provides a CuI-procatalyst for rapid sp2 C-H activation with cyclization involving transient CuIII species. The in situ generation of transient CuIII species was confirmed through online ultraviolet-visible spectroscopy (UV-vis), electrospray ionization mass spectrometry (ESI-MS), and X-ray photoelectron spectroscopy (XPS) analyses.

In Situ Generated Ag(II)-Catalyzed Selective Oxo-Esterification of Alkyne with Alcohol to α-Ketoester: Photophysical Study.

An expert and easy one-step catalytic method for the multi O-C coupling of alkyne is developed for the synthesis of valuable α-ketoesters and their chiral analogues, in contrast to the generation of esters by a noncatalytic method. The in situ generated powerful Ag(II) catalyst from AgOTf is the workhorse in the oxidative grafting of alkyne with PhIO and alcohol. The radical mechanism is confirmed in our controlled experiments and UV-vis study.

General base-tuned unorthodox synthesis of amides and ketoesters with water.

We discovered a highly reactive λ(3)-hypervalent iodane species using an inorganic/organic base for the unorthodox synthesis of amides and ketoesters through grafting terminal alkynes. In contrast to the metal-catalyzed dehydrative approaches the in situ generated nonmetallic reagent efficiently created C-N/C-O and C[double bond, length as m-dash]O bonds with amines/alkynes and water at rt.

Functionalised Mn(VI)-nanoparticles: an advanced high-valent magnetic catalyst.

We discover Mn(VI)-nanoparticles (NPs) bearing functional groups, high oxidation state, strong electron affinity, unique redox and paramagnetic nature, which opens up a new avenue to catalysis, magnetism and material application. However, its synthesis is challenging and remains unexplored because of associated serious difficulties. A simple benign synthetic strategy is devised to fabricate the high-valent NPs using mild reducing agent bromide, which transformed Mn(VII) to valuable Mn(VI)-species. The EELS-imaging of individual elements, ESI-MS, XPS and other techniques established its composition as Br(Me3SiO)Mn(VI)O2. It revealed significantly improved magnetic moment (SQUID) with isotropic hyperfine splitting of six line spectrum (EPR). The high-oxidation state and incorporated-ligands of the metals present on the active surface of the NPs led to development of a general catalytic process for oxidative heterodifunctionalisation to C-C triple bond towards formation of a new O-C/N-C/S-C and C-C coupling cum cyclisation to biologically important flavones and their aza- and marcapto-analogues, and valuable enaloxy synthons.

Ni(II)-salt catalyzed activation of primary amine-sp(3)Cα-H and cyclization with 1,2-diketone to tetrasubstituted imidazoles.

NiCl2·6H2O and Ni(OAc)2·4H2O were found as efficient catalysts for C-H activation of benzyl and aliphatic amines for an unprecedented multi C-N bond forming cyclization with 1,2-diketones under refluxing toluene to furnish highly substituted and polycyclic imidazoles.

ArCH(OMe)2--a Pt(IV)-catalyst originator for diverse annulation catalysis.

We discover an important property of a small molecule ArCH(OMe)2 which transforms catalytically inactive Pt(II)Br2 procatalyst in situ to an powerful catalyst Pt(IV)-species for diverse annulation reaction. The powerful catalytic system enables selective activation of C2-H/N-H and C2-H/C4-H of acetoacetanilide and C=O/C≡C of substituted butyne-1,2-dione for C-C/C-N, C-C/C-C and C-O/C-O bond-forming inter- and intramolecular annulation towards direct syntheses of functionalised 2-pyridones, cyclohexenones and 3(2H)-furanones respectively. In contrast to the common ligand, herein highly labile C-OMe bond of ArCH(OMe)2 is expected to react with PtBr2 towards generation of the high-valent active catalyst. Unlike catalyst promoter or initiator, the reaction does not occur with PtBr2 in the absence of ArCH(OMe)2. In situ generation of Pt(IV)-species and -OMe fragment of ArCH(OMe)2 were confirmed from the UV-vis characteristic peaks about 260 nm and trapping of -OMe group respectively. These observations provide new prospects and perspectives in catalysis for innovative catalyst design.

Synthetically useful noncatalytic strategy: a stereocontrolled rapid cyclization of a three component system to afford hexahydropyrrolizines.

We demonstrate a highly regio- and stereoselective annulation strategy involving unprecedented C2-H and N-H of proline esters, α,ß-unsaturated aromatic aldehydes and deactivated olefins without a catalytic aid to afford medicinally important pyrrolo[3,4-a]pyrrolizines and hexahydropyrrolizines under benign reaction conditions.

Efficient catalytic cyclizations of three and two imine assemblies: direct access to tetrahydroimidazo[1,5-c]imidazol-7-ones and imidazoles.

A cascade cyclization involving union of three imines by an organocatalyst proline is established to afford new fused-tetrahydroimidazo[1,5-c]imidazol-7-ones with excellent regio- and stereoselectivity. Another dehydrogenative cyclization by union of two imines is developed using the Cu(OTf)(2)-Ag(2)O combo catalyst to furnish functionalized imidazoles.

A fast and selective decarboxylative difunctionalization and cyclization for easy access to gem-dihalo alcohol, ether, ester and bromo-1,4-dioxane.

A general strategy for fast decarboxylative difunctionalization to gem-dihalohydrin, gem-dihaloether, gem-dibromoester and cyclized bromo-1,4-dioxane synthons with outstanding regio- and stereoselectivity is demonstrated.

Addition of halide to π-bond directly from aqueous NaX solution: a general strategy for installation of two different functional groups.

Activation of π-bond with organic Lewis acid and cationic surfactant mediated direct transfer of halides to alkyne and alkene are demonstrated to afford α,α-dihaloketones and other valuable synthons with outstanding selectivities.