Copper-Loaded Layered Bismuth Subcarbonate—Efficient Multifunctional Heterogeneous Catalyst for Concerted C–S/C–N Heterocyclization

Abstract

An efficient self-supported Cu(II)Bi(III) bimetallic catalyst with a layered structure was designed and developed. By careful characterization of the as-prepared material, the host structure was identified to exhibit a Sillen-type bismutite framework, with copper(II) ions being loaded as guests. The heterogeneous catalyst enabled C–N and C–S arylations under mild reaction conditions and with high chemoselectivities, thus furnishing valuable phenothiazines via heterocyclization with wide substrate tolerance. As corroborated by detailed catalytic studies, the cooperative, bifunctional catalyst, bearing Lewis acid sites along with copper(II) catalytic sites, facilitated an intriguing concerted C–N/C–S heterocyclization mechanism. The heterogeneous nature of the catalytic reactions was verified experimentally. Importantly, the catalyst was successfully recycled and reused multiple times, persevering its original structural order as well as its initial activity.

Sustainable Synthesis of Epoxides from Halohydrin Cyclization by Composite Solid-Based Catalysts

“…Postmortem XRD confirmed that these solids are crystalline Ca­(ClOH) (Figure S11). The additional data and the discussion are included in Sections S8 and S9 of the Supporting Information for demonstrating the heterogeneity of the presented reaction and the XRD patterns and photographs of spent catalysts …”

Sustainable synthesis of azobenzenes, quinolines and quinoxalines via oxidative dehydrogenative couplings catalysed by reusable transition metal oxide–Bi(iii) cooperative catalysts

“…The observed differences in the yields obtained are probably due to the catalytic activity of the composites in alcohol oxidation reactions. This is assumed given that all the catalysts have been shown to be active and reusable catalysts for the synthesis of various N-heterocycles, as shown previously, 92,94 so their abilities to promote alcohol oxidations must necessarily differ. As shown by the determined isolated yield of quinoxaline derivatives (63-85%) and the calculated E-factor of about 2.1-5.6, the developed process can be considered a green chemical process compared to the best available technologies in the fine chemical industry (Table S8 †).…”

“…We have recently shown that as-prepared bismutitesupported (Bi 2 O 2 CO 3 ) TMO cooperative catalysts 92,93 (referred to as MBi 2 O 2 CO 3 ; M = Co(II), Mn(II), Ni(II)) can enable efficient aerobic oxidative annulations to yield imines and benzimidazoles. 94 These inorganic composites practically meet the requirements of promising catalyst candidates to promote the proposed oxidative dehydrogenative crosscoupling reaction of (amino)anilines and diols.…”