RESUMO
Inherently chiral calixarenes have garnered significant attention due to their distinctive properties, yet the development of efficient catalytic asymmetric synthesis methods remains a critical challenge. Herein, we report the asymmetric synthesis of calix[4]arenes featuring inherent or both inherent and axial chirality via a cobalt-catalyzed C-H activation/annulation strategy in high yield with excellent enantio- and diastereoselectivity (up to > 99% ee and > 20:1 dr). Electrooxidation was also suitable for this transformation to obviate the sacrificial metal oxidants, underscoring the environmentally friendly potential of this approach. A key octahedral cobaltacycle intermediate was synthesized and characterized, providing valuable insights into the mode of enantio- and diastereocontrol of this protocol. Noteworthy photoluminescence quantum yields of up to 0.94 were measured, underscoring the potential of these compounds in the domain of organic fluorescent materials.
RESUMO
An unprecedented enantioselective synthesis of spiro-γ-lactams via a sequential C-H olefination/asymmetric [4+1] spirocyclization under a simple CoII /chiral spiro phosphoric acid (SPA) binary system is reported. A range of biologically important spiro-γ-lactams are obtained with high levels of enantioselectivity (up to 98 % ee). The concise, asymmetric synthesis of an aldose reductase inhibitor was successfully achieved. Notably, contrast to previous reports that relied on the use of cyclopentadienyl or its derivatives (achiral Cp*, CptBu , or chiral Cpx ) ligated CoIII complexes requiring tedious steps to prepare, cheap and commercially available cobalt(II) acetate tetrahydrate was used as an efficient precatalyst.
RESUMO
An unprecedented synthesis of valuable benzofuran-3(2 H)-one scaffolds with a quaternary center was developed via Rh/Co relay catalyzed C-H functionalization/annulation of N-aryloxyacetamides with propiolic acids in moderate to good yields. The reaction features the simultaneous construction of the benzofuran motif containing a C2 quaternary center and a C3 carbonyl group. The preliminary mechanism study verified that the O atom of C3 carbonyl group originates from molecular oxygen.
RESUMO
An efficient synthesis of thiazolidine-2,4,5-triimine derivatives was developed via Ni-catalyzed oxidative double isocyanide insertion to thioureas under air conditions, in which thioureas play three roles as a substrate, a ligand, and overcoming isocyanide polymerization. The reaction is featured by employing a low-cost and low loading Ni(acac)2 catalyst, without any additives, and high atom economy. This is the first example to directly apply a Ni(II) catalyst in oxidative double isocyanide insertion reactions.
RESUMO
A new CuI/1,10-phen-catalyzed reaction for the synthesis of 3-ylideneoxindoles from readily available isatins and ethyl isocyanoacetate, in which ethyl isocyanoacetate acts as a latent two-carbon donor like the Wittig reagent, is reported. A tandem procedure including 1,3-dipolar cycloaddition/inverse 1,3-dipolar ring opening/olefination allows the preparation of 3-ylideneoxindoles with broad functional group tolerance.
RESUMO
A concise and direct synthetic strategy for the construction of 2-aryliminochromene skeleton by cascade three-component coupling reaction of arynes, N,S-keteneacetals, and DMF in good yields has been disclosed. The process demonstrates the first example of aryne chemistry combined with N,S-keteneacetals. Using this strategy, an expeditious synthesis of biologically important arylimino-2H-chromene-3- carboxamides was achieved.
RESUMO
A facile and efficient method for the chemoselective synthesis of benzo[e]pyrazolo[1,5-c][1,3]thiazine derivatives has been developed by tandem Ullmann coupling reactions of ß-oxodithioesters (ODEs) with 3-(2-bromoaryl)-1H-pyrazoles in C-S bond formation manner, in which ODEs play dual roles as both a substrate and a ligand. A series of benzo[e]pyrazolo[1,5-c][1,3]thiazine derivatives were provided in good to excellent yields with CuI as the copper source in the presence of NaOH in CH3CN at 80 °C under a N2 atmosphere.
Assuntos
Cobre/química , Pirazóis/síntese química , Compostos de Sulfidrila/química , Tiazinas/síntese química , Catálise , Estrutura Molecular , Pirazóis/química , Tiazinas/químicaRESUMO
Highly substituted cyclopentenes can be accessed rapidly from isocyanides, aldehydes and malononitrile or ethyl cyanoacetate (AB2C2) using DABCO as a catalyst under solvent-free conditions at 40 °C within 30 min.