Development
of novel and greener methods for the selective oxidation
of various organic compounds is a challenging task. Herein, a novel
protocol for the selective oxidation of aromatic amines to nitroaromatics
at room temperature is developed. The oxidation reaction was carried
out using a mixture of formic acid and aqueous hydrogen peroxide,
which resulted in the in situ formation of performic acid. Further,
improvement of selectivity was studied using different surfactants,
of which cetyltrimethylammonium bromide (CTAB) gave the highest selectivity
(85%) toward nitrobenzene. The role of CTAB in achieving higher selectivity
is discussed. Under optimized reaction conditions, various substituted
amines were successfully oxidized to corresponding nitro compounds.
It is worth mentioning that this is the first report on oxidation
of amines to nitro compounds in an aqueous medium with high selectivity.
An
efficient protocol involving the transformation of sequentially
generated recursive anions from heterocyclic precursors to orthogonally
strap diynones through one pot transition-metal-free spirocyclopentannulation
has been devised, employing oxindoles and pyrazolones as prototypical
platforms. Insights into these regioselective tandem Michael–anti-Michael processes have been gleaned through DFT calculations.
The stereoelectronic effects are crucial in governing the conformational behaviour of the small molecules bearing heterocyclic ring adjacent to amides. It dictates the antagonist and agonist activity for G-protein coupled...
Globally 3 billion people are consuming water with moderately high concentrations of fluoride and arsenic. The development of a simple point of care (PoC) device or home device for the detection of fluoride/arsenic ensures safety before consuming water. Till date, lateral flow assay (LFA) based PoC devices can detect nucleic acids, viruses and diseases. An aluminium complex of rhodamine B functionalized oxacalix[4]arene (L) was designed to execute the LFA-based PoC device. Initially, Al3+ and Fe3+ ions were involved in complexation with the rhodamine B functionalized oxacalix[4]arene (L), resulting C1 (L-Al3+) and C2 (L-Fe3+) complexes respectively. The receptor L, as well as the probes (C1, C2), were characterized thoroughly using mass spectroscopy, FTIR, NMR, and EA. C1 and C2 were further utilized as recyclable probes for the detection of aqueous fluoride (21 ppb) and arsenate (1.92 ppb) respectively. The computational calculation indicates that upon complexation, the spirolactam ring opening at the rhodamine B site leads to optoelectronic changes. The consistency of LFA-based portable sensing device has been tested with water samples, synthetic fluoride standards and dental care products like toothpaste and mouthwash with concentrations ≥ 3 ppm. Moreover, fixed cell imaging experiments were performed to ascertain the in-vitro sensing phenomena.
α-heterosubstituted 1,3-dioxane and 1,3-dithiane systems have been extensively reported for n_( X) → σ_(C-Y)^* (X, Y = heteroatoms) hyperconjugative interactions. However, the definitive interpretation for the conformational analysis of 2-carbomethoxy...
α-heterosubstituted 1,3-dioxane and 1,3-dithiane systems have been
extensively reported for n_( X) → σ_(C-Y)^* (X, Y = heteroatoms)
hyperconjugative interactions. However, the definitive interpretation
for the conformational analysis of 2-carbomethoxy
1,3-diheterocyclohexane is less explored. The weaker accepting ability
of C-C(carbomethoxy) antibonding orbitals in 2-substituted
1,3-diheterocyclohexane makes it an attractive candidate for estimating
the role of stereoelectronic effects in such systems. This study
explores conformational preferences of 2-carbomethoxy substituted
1,3-dioxane, 1,3-oxathiane and 1,3-dithiane in the light of
stereoelectronic interactions and the contribution of other factors to
attain stability in the respective systems. The DFT calculated results
in the solvent phase reveal the delocalizing interactions operate in all
the three systems examined; however, ring strain override the axial
preference of 2-carbomethoxy substituent on 1,3-dioxane (2-ax) and
1,3-oxathiane (3-ax). The hyperconjugative interaction, lower ring
strain and attractive C-H∙∙∙O non-bonded interactions favor axial (4-ax)
over equatorial (4-eq) isomer of methyl-2-carboxylate-1,3-dithiane.
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