Asian Journal of Organic Chemistry最新文献

A photoinduced Wolff rearrangement/chiral isothiourea catalyzed [4+2] cycloaddition reaction of pyrazolone derivatives and α-diazoketones was developed, affording the corresponding dihydropyrano[2,3-c]pyrazolone derivatives in moderate to good yields (50–94 %) with satisfactory to excellent diastereoselectivities (>20 : 1 dr, in almost all cases) and enantioselectivities of 31–99 %. This protocol features readily available substrates, mild reaction conditions, and effective construction of vicinal tertiary and quaternary carbon stereocenters.

A simple synthesis of 3-hydroxy-2-(2-nitro-1-arylethyl)cyclohex-2-en-1-ones, 3-hydroxy-5,5-dimethyl-2-(2-nitro-1-arylethyl)cyclohex-2-en-1-ones and 4-hydroxy-3-(2-nitro-1-arylethyl)pent-3-en-2-ones via conjugate addition of cyclic 1,3-diketones, 1,3-cyclohexanedione and 5,5-dimethyl-1,3-cyclohexanedione and acyclic 1,3-diketone, pentane-2,4-dione to β-Nitrostyrenes were reported. This methodology is pleasing with reliability and scalability with gram scale products that can be synthesized.

Cyclam is a well-known example of a polyaza macrocycle. However, there are few reports of its optically active versions. In this study, we synthesized highly symmetric optically active cyclam (S,S,S,S)-5,7,12,14-tetraphenyl-1,4,8,11-tetraazacyclotetradecane, which has four phenyl groups on the cyclam skeleton, and derivatized it in various ways. We were able to synthesize a chiral Cu complex, an N-ethyl derivative, and a dithiourea from this optically active cyclam. The structures of the chiral Cu complex and dithiourea were verified by single-crystal X-ray diffraction analysis.

An eco-friendly and efficient method was developed for synthesizing a novel class of aliphatic sulfonyl fluorides in a catalyst-free one-pot reaction. The new approach offers a streamlined synthesis for N-(Substituted)-2-(fluorosulfonyl) ethyl carbamodithioates by combining amines, carbon disulfide, with ethenesulfonyl fluoride. The synthesized compounds were obtained in good yields under mild conditions, making this reaction a valuable tool for exploring new chemical transformations.

A method for the synthesis of new heterocyclic system representatives, i. e. imidazo[4,5-d]thiazolo[4,3-b]oxazole derivatives, by the reaction of thioglycolurils with α-bromoketones has been developed. The reaction includes a cascade one-pot S-alkylation/nucleophilic addition/ring-opening/ring-closing process. This protocol is compatible with a broad scope of α-bromoketones, diastereoselectively affording diverse products with 3aS*,4aR*,8aR*-imidazo[4,5-d]thiazolo[4,3-b]oxazole core in 40–76 % yields.

A series of Cu-based mixed oxides were prepared by calcinations of corresponding CuMgAl-layered double hydroxides precursors at different temperatures with nominal Cu/Mg/Al ratios of 1 : 1 : 2(Cu-LDH-1), 1 : 2 : 1(Cu-LDH-2),1 : 1 : 1(Cu-LDH-3), and 2 : 1 : 1(Cu-LDH-4). The synthesized catalysts were characterized using X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and N₂ physisorption analysis techniques. All as-obtained catalysts showed adequate catalytic performance for the α-alkylation of ketones with alcohols through a hydrogen autotransfer mechanism. The catalyst CuMgAl-I-650 (obtained by calcining Cu-LDH-1 at 650 °C) displayed the highest activity and selectivity. Using this catalyst system, a wide range of branched ketones were synthesized in good to excellent isolated yields. Moreover, the catalyst CuMgAl-I-650 could be recycled and reutilized for four cycles without any significant loss of activity and selectivity. This study provides a very simple and inexpensive catalysis based on transition metals, which are in abundance on earth.

A facile method for the preparation of meso-1,2-diarylethane-1,2-diamines from aromatic aldehydes is disclosed. The stereoselectivity of the protocol is based on the disrotatory electrocyclic ring closure of readily generated diazopentadienes, followed by a SET reduction of the imidazoline fragment by sodium. The method is readily scalable to multi-gram quantities and a wide range of alkoxy and alkyl-phenyl substituents can be synthesized.

Thiourea dioxide (TDO) has been demonstrated to be an efficient reagent for the transformation of aromatic, heteroaromatic, alkenyl and aliphatic aldoximes to respective nitriles in excellent yields. Furthermore, this method has been applied to the synthesis of fungicide cyazofamid from a commercial precursor using TDO as a pivotal dehydrating and reducing reagent. This new procedure offers simple and easily reproducible technique for nitrile synthesis and highlights the synthetic utility of TDO as a versatile reagent in organic chemistry.

The development of phosphine ligands continues to be essential for palladium-catalyzed homogeneous carbonylation reactions, particularly in achieving high regioselectivity. In this study, a cyclosiloxane-based multi-dentate phosphine ligand, L1 (V4-4Ph₂P), characterized by its high thermal stability and oxidation resistance, was synthesized through the radical addition of secondary phosphines to the double bonds of tetravinyltetramethylcyclotetrasiloxane. L1 was then used in the Pd-catalyzed alkoxycarbonylation of a variety of olefins, including terminal and internal alkenes, cyclic alkenes, aromatic terminal alkenes as well as tetra-, tri- and 1,1-disubstituted alkenes to afford the desired esters with moderate to good yields. As elucidated via DFT calculations and in situ IR spectroscopy, the optimum spatial chelation modes and high stability of Pd−H active species were responsible for the enhancement of catalytic efficiency.