In the present work, a novel donor (D)–acceptor
(A) fluorophore based on indeno-pyrrole derivative (PYROMe) has been
utilized as a dual sensor for volatile acids and aromatic amines,
where sensory responses were regulated by the aggregation-induced
emission (AIE) property. The twisted structural framework of PYROMe,
confirmed by crystal study, avoids closed cofacial encounter upon
aggregation and aided with augmented rigidity via different noncovalent
interactions that ultimately ensued restricted intramolecular rotation
(RIR). Consequently, PYROMe exhibited AIE in THF/H2O mixture
along with bright solid-state emission. The accessibility of protonation
at carbonyl site and feasible HOMO energy to accept electrons from
aromatic amines during photoexcitation enabled PYROMe as a potential
dual sensor. A thin film of PYROMe was utilized for the quantitative
detection of volatile acids and aromatic amines, and the detection
limit (DL) was found to be as low as 0.77 ppm and 6.04 ppb for trifluoroacetic
acid (TFA) and aniline vapors, respectively. Beyond the established
scopes of substituted indeno-pyrroles, the present study paves the
way, for the first time, toward an AIE-driven dual-stimuli response
in indeno-pyrrole based D–A fluorophores.
The α,α‐dihalocarbonyl moiety is a bifunctional system with a gem‐dihalocarbon and a carbonyl carbon in 1,2‐fashion. This is one of the privileged scaffolds in medicinal chemistry due to its chemical and metabolic stability and lipophilicity. They have also been found in numerous structurally divergent natural products and most of their fabricated structures have already been in medicinal use. Apart from their important use in medicinal chemistry, the α,α‐dihalocarbonyl groups have been employed as key building blocks for the development of novel synthetic strategies and utilized as intermediates in total synthesis. In addition to the traditional transformations such as oxidations, reductions, and C−C bond formations, recently several new and non‐classical reactions have also been developed. This review provides short description of existing methods for their synthesis and detailed discussion on the efforts for the discovery and development of new reactions by employing α,α‐dihaloketones as synthetic building blocks. We have presented their use as key functional groups for the synthesis of polycyclic systems of medicinal and material importance and natural products.
We have developed am etal-free, N-iodosuccinimide (NIS)-promoted, cascade strategy for the efficient synthesis of biologically important indeno[1,2-c]pyrroles via a[ 3 + +2] annulation process of enamine-alkynes.T his methodology had shown av ery broad scope for diversely functionalized enamines and alkynes.W eh ave also developed ao nepot, multicomponent strategyf or the direct synthesis of indeno-pyrrolesf rom diynones via enamine-alkynes. Control experiments supported the involvement of NIS as an electrophilic activator via an ionic mechanism rather than aradical pathway.Scheme 5. One-pot, multicomponent strategyf or the direct synthesis of indeno[1,2-c]pyrroles from diynones.Scheme6.Control experiments and proposed mechanism.
A mild strategy for highly regioselective hydration of the alkynes (internal and terminal) has been developed employing intramolecular ketone as the directing group under Ag(I) catalysis. In this process both internal and terminal alkynes exhibited 100 % complementary reactivity i. e. 6‐endo‐dig vs. 5‐exo‐dig respectively, and provided two regio‐isomeric dicarbonyl products as exclusive products. This process found very broad scope for the ketones and alkynes. The 1,5‐diketones were efficiently transformed in to synthetically and pharmaceutically important naphthalene derivatives employing an intramolecular Aldol condensation.
We report the discovery of an anomalous reaction of 2‐(alkynonyl)alkynylbenzenes under AgI catalysis for the selective formation of isocoumarins. This reaction is previously undocumented for 2‐(alkynonyl)alkynylbenzenes in terms of the reaction mechanism and the product formed. Water (H2O18) labeling studies suggested a possible mechanistic pathway in which the initial formation of a pyrylium ion is followed by hydrative dealkynylation, that is, water incorporation and alkyne expulsion, similar to a retro‐Favorskii reaction.
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