Visible
light-mediated photocatalytic organic transformation has
drawn significant attention as an alternative process for replacing
thermal reactions. Although precious metal/organic dyes based homogeneous
photocatalysts have been developed, their toxic and nonreusable nature
makes them inappropriate for large-scale production. Therefore, we
have synthesized a triazine and a keto functionalized nonmetal based
covalent organic framework (TpTt) for heterogeneous photocatalysis.
As the catalyst shows significant absorption of visible light, it
has been applied for the photocatalytic uphill conversion of trans-stilbene to cis-stilbene in the presence
of blue light-emitting diodes with broad substrate scope via an energy
transfer process.
Here, the first example is reported of a new, molecularly defined SNS-cobalt(ii) catalyst for the acceptorless dehydrogenative coupling (ADC) of unprotected amino alcohols with secondary alcohols leading to pyrrole and pyridine derivatives.
We report here for the first time the catalytic oxidative dehydrogenation of N-heterocycles by a visible-light organo-photoredox catalyst with low catalyst loading (0.1-1 mol %). The reaction proceeds efficiently under base- and additive-free conditions with ambient air at room temperature. The utility of this benign approach is demonstrated by the synthesis of various pharmaceutically relevant N-heteroarenes such as quinoline, quinoxaline, quinazoline, acridine, and indole.
Development of multicatalytic approach consisting of two or more mechanistically distinct catalytic steps using a single-site catalyst for rapid and straightforward access of structurally complex molecules under eco-benign conditions has significance in contemporary science. We have developed herein a rhodium-catalysed C–H activation strategy which uses an unprotected anilines and an electron-deficient alkynes to C–C bonded products as a potential intermediate in contrast to the archetypical C–N bonded products with high levels of regioselectivity. This is followed by carbonylation of C–H bond activated intermediate and subsequent annulation into quinolines has been described. This rhodium-catalysed auto-tandem reaction operates under mild, environmentally benign conditions using water as the solvent and CO surrogates as the carbonyl source with the concomitant generation of hydrogen gas. The strategy may facilitate the development of new synthetic protocols for the efficient and sustainable production of chemicals in an atom-economic way from simple, abundant starting materials.
Direct synthesis of N-heterocycles via the acceptorless
dehydrogenative coupling is very challenging and scarcely reported
under 3d transition-metal catalysis. Here, we have developed an efficient
Mn(I)-catalyzed sustainable synthesis of various quinoxalines from
1,2-diaminobenzenes and 1,2-diols via the acceptorless
dehydrogenative coupling reaction. Further, this strategy was successfully
applied for the unprecedented synthesis of quinazolines by the reaction
of 2-aminobenzyl alcohol with primary amides. The present protocol
provides an atom-economical and sustainable route for the synthesis
of various quinoxaline and quinazoline derivatives by employing an
earth-abundant manganese salt and simple phosphine-free NNN-tridentate
ligand.
Children under 19 years of age constitute over 40% of India's population and information about their mental health needs is a national imperative. Children with specific learning disorders (SLDs) exhibit academic difficulties disproportionate to their intellectual capacities. Prevalence of SLD ranges from 2% to 10%. Dyslexia (developmental reading disorder) is the most common type, affecting 80% of all SLD. About 30% of learning disabled children have behavioral and emotional problems, which range from attention deficit hyperactivity disorder (most common) to depression, anxiety, suicide etc., to substance abuse (least common). Co-occurrence of such problems with SLD further adds to the academic difficulty. In such instances, diagnosis is difficult and tricky; improvement in academics demands comprehensive holistic treatment approach. SLD remains a large public health problem because of under-recognition, inadequate treatment and therefore merits greater effort to understand the co-morbidities, especially in the Indian population. As the literature is scarce regarding co-morbid conditions in learning disability in Indian scenario, the present study has tried to focus on Indian population. The educational concessions (recent most) given to such children by Central Board of Secondary Education, New Delhi are referred to. The issues to be addressed by the family physicians are: Low level of awareness among families and teachers, improper dissemination of accurate information about psychological problems, available help seeking avenues, need to develop service delivery models in rural and urban areas and focus on the integration of mental health and primary care keeping such co-morbidity in mind.
An external oxidant-free, base-free direct C–H arylation of anilides by visible-light mediated metal-free photoredox catalysis in tandem with palladium catalysis is described. The reaction operates at room temperature, without a silver-salt activator and additives, and no generation of copious metal waste.
The development of robust catalytic systems based on base‐metals for reversible acceptorless dehydrogenation (ADH) and hydrogenation of feedstock chemicals is very important in the context of ‘hydrogen storage’. Herein, we report a highly efficient reusable cobalt‐based heterogeneous catalyst for reversible dehydrogenation and hydrogenation of N‐heterocycles. Both the ADH and the hydrogenation processes operate under mild, benign conditions.
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