Metal complex catalysis in the synthesis of quinolines

The synthesis, photophysical, and electrochemical attributes of a novel class of boron difluorides containing an aromatic-fused alicyclic/hetero-alicyclic ring built on a β-iminoenamine chromophoric backbone are reported. The compounds displayed large Stokes shifts (86–121 nm), and were emissive in the solid state. The quantum yields obtained in solution at room temperature were unusually lower by an order of magnitude compared to those in the solid state. Some of the tested compounds displayed aggregation-induced emission (AIE). Single crystal XRD analyses revealed a lack of interplanar π–π interactions, which are presumed to be absent owing to non-planarity of the alicyclic component in the molecule. For most of the studied compounds, time-dependent DFT (TD-DFT) calculations invariably reveal intramolecular charge transfer (π–π*) characteristics with the frontier orbitals concentrated on the boron–nitrogen heterocycle. The participation of boron and fluorine atoms was found to be negligible.

β-Iminoenamine-BF2 complexes: aggregation-induced emission and pronounced effects of aliphatic rings on radiationless deactivation.

A novel, highly modular synthetic method with high functional group tolerance was developed for the construction of chromenoquinoline derivatives from arylpropynyloxy-benzonitriles and diaryliodonium triflates via an oxidative arylation-cyclization path. The copper(I) chloride catalyzed reaction is presumed to involve the formation of highly active arylcopper(III) species.

Modular Copper-Catalyzed Synthesis of Chromeno[4,3-b]quinolines with the Utilization of Diaryliodonium Salts

The photolysis of propiconazole in pure water, in water containing humic substances, and in natural water was investigated. The reaction rates were determined, and the main photoproducts were identified with the help of HPLC−mass spectrometry and by NMR. The quantum yield for direct photolysis was 0.11 ± 0.01 at the maximum of absorption (269 nm). Photocyclization after HCl elimination and photohydrolysis of the cyclized intermediate were the main reaction pathways at 254 nm. By contrast, oxidation prevailed over dechlorination in simulated or natural solar light. Humic substances (10 mg·L-1) and naturally occurring chromophores contained in natural water enhanced the rate of propiconazole photodegradation in solar light. Half-life in June in Clermont-Ferrand (latitude 46°N) was found to be 85 ± 10 h in pure water and 60 ± 10 h in natural water; showing that photodegradation of propiconazole in natural waters involves both direct photolysis and photoinduced reactions. Keywords: Propiconazole; direct photo...

K.S. Swaminathan

Papers

A novel photochemical cyclisation of 4-chloro-3-(N-Aryliminomethyl) (2H)benzopyrans and benzothiopyrans