A mild method for an efficient synthesis of C3-naphthyl indoles from
-alkynylacetophenones has been developed. This Ag-catalyzed transformation is assisted by the acetal formed under the reaction ...condition employing trimethyl orthoformate (TMOF). The role of acetal in promoting the reaction under ambient conditions has been established with control experiments. A range of C3-naphthyl indole derivatives have been synthesized in moderate to very good yields.
Fluorene‐based polyaromatic hydrocarbons are renowned compounds for materials applications. Herein, a straightforward route via in situ acetal formation has been presented to access benzoafluorenes ...by a triflic acid promoted cationic cycloisomerization of enynones in presence of trimethyl orthoformate under metal‐free conditions. In the absence of trimethyl orthoformate, the same reaction results in benzoafluorenones. All the synthesized benzoafluorenones are highly fluorescent in solution phase with high Stokes shift while the corresponding benzoafluorenes are not fluorescent.
An interesting domino reaction for the synthesis of substituted naphthyl ketones has been developed using readily accessible starting materials. This domino reaction proceeds via in situ ...incorporation of an acetal followed by intramolecular heteroalkyne metathesis/annulation in an ortho-alkynylacetophenone derivative. A deuterium incorporation experiment has been carried out to understand the mechanism.
Nucleophilic addition of cyanide on a new triphenylamine attached difluoroboron β‐diketonate {4‐4‐(diphenylamino) phenyl‐2,2‐difluoro‐6‐methyl‐2H‐1,3,2‐dioxaborinin‐1‐ium‐2‐uide (C4)} breaks the ...conjugation readily and thereby offers efficient and selective detection of cyanide. A rational mechanism based on UV/Vis, fluorescence, NMR (1H, 11B, and 19F) and HRMS analysis and DFT calculations has been proposed. The detection limit was found to be 0.36 µM. A test strip assay using the title compound has also been applied to detect CN– in aqueous solution for real‐time applications.
A triphenylamine linked difluoroboron β‐diketonate based sensor can detect cyanide ion in organic–aqueous media with high selectivity and sensitivity. The probe embedded in cellulose test strip enables naked‐eye detection of CN– in a neat aqueous medium.
A wide range of substituted pyridine derivatives were synthesized in moderate to good yields from N‐propargylic α‐enamino esters. The synthetic strategy involved regioselective addition of a ...propargylamine to the α‐carbon atom of an alkynyl ester to produce the N‐propargylic α‐enamino ester, which acted as the key intermediate in the synthesis.
An efficient synthesis of substituted pyridines through the cyclization of easily accessible N‐propargylic α‐enamino esters is described. This method involves regioselective addition of propargylamines to alkynyl esters to produce N‐propargylic α‐enamino esters, which act as the key intermediates in the synthesis.
A new protocol has been developed for the synthesis of indene derivatives in a diastereoselective manner from o-alkenylbenzaldehydes and enolizable ketones in the presence of trimethyl orthoformate ...and catalytic triflic acid. This method involves tandem in situ formed acetal-assisted Claisen–Schmidt condensation followed by 5-exo-trig cyclization/Michael addition in one-pot. It has also been shown that the chalcones derived from o-alkenylbenzaldehydes and ketones can effectively be transformed into indene derivatives in the presence of TfOH catalyst alone.
An intramolecular approach to generate compounds containing an arylnaphthalene lignan scaffold in high yields is presented. It involves a sequential intramolecular electrophilic attack of carbonyl on ...arylalkyne followed by benzannulation catalyzed by gold salt. AuCl(3) in combination with AgSbF(6) works better to effect this transformation. Selected products have been converted into arylnaphthalene lactone natural products such as justicidin E, taiwanin C, and retrojusticidin B.
Using the in‐situ‐formed acetal strategy, a facile approach has been developed to synthesize naphthalene derivatives from o‐alkynylbenzaldehydes and enolizable ketones. In situ acetal formation ...assists the condensation between o‐alkynylbenzaldehydes and enolizable ketones to give chalcone derivatives under Brønsted acidic conditions. In situ acetal formation facilitates the reaction by increasing the electrophilicity of the carbonyl carbon of the o‐alkynylaldehyde through oxonium ion formation, and also by enhancing the nucleophilicity of the α carbon of the ketone through the formation of an enol ether. The formed chalcones undergo trans to cis isomerization to effect alkyne–carbonyl metathesis to give naphthalene derivatives.
In situ acetal formation assists the intermolecular cyclization of o‐alkynyl aryl aldehydes with enolizable ketones to give diverse naphthyl ketone derivatives under metal‐free catalytic conditions.
An interesting gold-catalyzed electrophilic addition to arylalkyne to synthesize substituted naphthalenes has been presented. Different metal hexafluoroantimonates have also been found to effect the ...transformation. Counter anion and oxo- and alkynophilicities of catalytic gold species might play an important role in this annulation reaction.
Gold(III)chloride in catalytic amounts activates 3,4,6-tri-O-acetyl-d-glucal, 3,4,6-tri-O-acetyl-d-galactal, and 3,4-di-O-acetyl-l-rhamnal efficiently. The activated species can be employed in the ...Ferrier reaction with different nucleophiles at ambient conditions. Attempts have been made to make β-anomer of the Ferrier product from anomeric-O-propargylated Ferrier product.
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