Gold-catalyzed oxycyclization of allenic carbamates: expeditious synthesis of 1,3-oxazin-2-ones

Khan

ACS Sustainable Chem. Eng.

et al. 2020

The present work introduces the favorable synthesis of porous functionalized nanomaterials with excellent surface area, porosity, and high CO 2 capture ability to facilitate cyclizative reactions by incorporating the CO 2 molecule into highly reactive organic moieties. We have attempted to fulfill the target by the decoration of Ag NPs over the exterior surfaces of covalent organic frameworks (COFs) TpPa-1 and TpTta to achieve Ag@TpPa-1 and Ag@TpTta nanomaterials with an absolutely ordered structure. Characterizations of the nanocatalysts (Ag@TpPa-1 and Ag@ TpTta) have been performed by field emission scanning electron microscopy, thermogravimetric tools, N 2 adsorption/desorption, transmission electron microscopy, Fourier transform infrared spectroscopy, UV−vis, and powder X-ray diffraction analysis. These Ag NPs architectured porous COFs described excellent performance for the benign synthesis of cyclic carbamates from unsaturated amines in the presence of N-iodosuccinimide (NIS) and several 2-oxazolidinone derivatives from propargylamine derivatives via cyclizative atmospheric CO 2 capture under solvent-free and alkali-free conditions (sustainable approach). The microporous material Ag@TpTta revealed most excellent catalytic performance than Ag@TpPa-1during production of cyclic carbamates and oxazolidinones which indicates that the selection of Ag NPs decorated COFs with the excellent surface area has a contributory effect on carboxylative cyclization reaction. Density functional theory studies furnished important information to establish the detailed mechanism of silver (0) catalyzed CO 2 incorporation into unsaturated amine. These COFs enriched with N centers can interact with the Ag NPs at their outer exterior surfaces very tightly. These two nanocatalysts exhibited magnificent recycling efficiencies for the generation of cyclic carbamates and 2-oxazolidinones with almost zero silver leaching from the exterior part of the catalyst.

Section: Resultsmentioning

confidence: 99%

Utility of Silver Nanoparticles Embedded Covalent Organic Frameworks as Recyclable Catalysts for the Sustainable Synthesis of Cyclic Carbamates and 2-Oxazolidinones via Atmospheric Cyclizative CO₂ Capture

Khan

ACS Sustainable Chem. Eng.

et al. 2020

“…In order to prepare a library of new imidazo[1,2- c ][1,3]oxazin-5-one heterocycles, N -Boc-4-bromo-5-methyl-2-phenylethynylimidazole 1a was studied as a model substrate and subjected to some annulation process conditions which have been already described in the literature. 25,37,46,49,50,57–64 Compound 1a , which is a suitable substrate for undergoing intramolecular annulation, was prepared following our recent procedure involving the regioselective Sonogashira cross coupling reaction of N -Boc-2,5-dibromo-4-methylimidazole. 48 Initially, the zinc catalyst (ZnCl 2 ) was used in dichloromethane at 40 °C but it was found to be totally inert since the starting material was completely recovered after 48 h (Table 1, entry 1).…”

Section: Resultsmentioning

confidence: 99%

A Ag₂CO₃/TFA-catalyzed intramolecular annulation approach to imidazo[1,2-c][1,3]oxazin-5-one derivatives

et al. 2022

“…We then attempted to protect the hydroxyl group, but found that the resultant allene 29 underwent Au‐mediated cyclization to produce cyclic carbamate 30 . This undesired product probably results from the attack of the carbamate to allene through the oxygen rather than the nitrogen atom . To fix this problem, we decided to let the free amine attack the allene moiety.…”

Section: Figurementioning

confidence: 99%

Total Synthesis of Lapidilectine B Enabled by Manganese(III)‐Mediated Oxidative Cyclization of Indoles

Gao

Fan

Geng

et al. 2018

Chemistry A European J

A novel manganese(III)-mediated oxidative cyclization of readily accessible 1,2,3-trisubstituted indoles is described. This unprecedented method enabled the efficient construction of a complex polycyclic scaffold bearing a spiro-indoline motif and a lactone moiety in one step. Its synthetic utility was demonstrated in the total synthesis of lapidilectine B (in 18 steps) by employing a strategic regioselective ring-expansion and a silver-promoted allenic amine cyclization as the additional key elements.