This report describes synthesis of a new class of secondary interactions (SeCH….Cl) controlled molecular rotor having Cl−Pd−Cl rotor spoke, attached on a Se−Pd−Se axle. Variable temperature NMR data establish ΔG⧧298K/ΔG⧧350K...
Rhodium(III)-catalyzed dehydrogenative annulation of 2-aryl-imidazo[1,2-a]pyridines with maleimides is described. The reaction afforded 1H-benzo[e]pyrido[1',2':1,2]imidazo[4,5-g]isoindole-1,3(2H)-diones in high yields with wide range of functional group tolerance. The reaction proceeds through Rh(III)-catalyzed CÀ H bond activation, followed by maleimide insertion and intramolecular cyclization. Photophysical properties of 1H-benzo[e]pyrido[1',2':1,2]imidazo[4,5-g]isoindole-1,3(2H)-diones were studied with UVvisible and fluorescence spectroscopy and validated by quantum chemical calculations. All the annulated products showed large Stokes shift values with emission in the range of 530-618 nm, and moderate to high quantum yields.
This report describes the syntheses of three new trans‐palladium dichloride complexes of bulky selenium ligands. These complexes possess a Cl−Pd−Cl rotor spoke attached to a Se−Pd−Se axle. The new ligands and palladium complexes (C1−C3) were characterized with the help of NMR, HRMS, UV‐Vis., IR, and elemental analysis. The single‐crystal structure of metal complex C2 confirmed a square planar geometry of complex with trans‐orientation. The X‐ray structure revealed intramolecular secondary interactions (SeCH—Cl) between chlorine of PdCl2 and CH2 proton of selenium ligand. Variable‐temperature NMR data shows coalescence of diastereotopic protons, which indicates pyramidal inversion of selenium atom at elevated temperature. The relaxed potential energy scan of C2 suggests a rotational barrier of ∼12.5 kcal/mol for rotation of chlorine atom through Cl−Pd−Cl rotor. The complex C3 possesses dual intramolecular secondary interactions (OCH2—Cl and SeCH2—Cl) with stator ligand. Molecular rotor C2 was found to be a most efficient catalyst for the decarboxylative Heck‐coupling under mild reaction conditions. The protocol is applicable to a broad range of substrates with large functional group tolerance and low catalyst loading (2.5 mol %). The mechanism of decarboxylative Heck‐coupling reaction was investigated through experimental and computational studies. Importantly the reaction works under silver‐free conditions which reduces the cost of overall protocol. Further, the catalyst also worked for decarboxylative arylation and decarboxylative Suzuki‐Miyaura coupling reactions with good yields of the coupled products.
A simple and straightforward approach has been realized for the direct regioselective benzoylation of imidazoheterocycles by oxidative decarboxylation of arylglyoxylic acids in the presence of K2S2O8 as oxidant. Various functional...
A facile and efficient synthetic
method for the construction
of
C3-hydroxyalkylated imidazo[1,2-a]pyridines and indoles
by a Zn(OTf)2-catalyzed Friedel–Crafts hydroxyalkylation
of imidazo[1,2-a]pyridines and indoles with carbonyl
compounds under mechanochemical conditions is reported. Good product
selectivity, shorter reaction time, ambient reaction temperature,
tolerance of a wide range of functional groups, broad substrate scope,
moderate to good yield of products, and scalability are the salient
features of the developed methodology.
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