Consecutive three-component synthesis of film luminescent indolone merocyanines with L-amino acid ester donors

Multicomponent synthesis of chromophores – The one-pot approach to functional π-systems

Multicomponent reactions, conducted in a domino, sequential or consecutive fashion, have not only considerably enhanced synthetic efficiency as one-pot methodology, but they have also become an enabling tool for interdisciplinary research. The highly diversity-oriented nature of the synthetic concept allows accessing huge structural and functional space. Already some decades ago this has been recognized for life sciences, in particular, lead finding and exploration in pharma and agricultural chemistry. The quest for novel functional materials has also opened the field for diversity-oriented syntheses of functional π-systems, i.e. dyes for photonic and electronic applications based on their electronic properties. This review summarizes recent developments in MCR syntheses of functional chromophores highlighting syntheses following either the framework forming scaffold approach by establishing connectivity between chromophores or the chromogenic chromophore approach by de novo formation of chromophore of interest. Both approaches warrant rapid access to molecular functional π-systems, i.e. chromophores, fluorophores, and electrophores for various applications.

Binaphthyl-Stabilized Palladium Nanoparticle-Catalyzed Stereoselective Synthesis of 3-Arylidene-2-oxindoles via One-Pot Heck-like Carbocyclization/Nucleophilic Addition

Stereoselective, one-pot synthesis of 3-arylidene-2-oxindoles has been accomplished via Heck-like carbocyclization/nucleophilic addition of N-(2-iodophenyl)-N-methyl-3-phenylpropiolamide, phenylacetylene, and secondary amine using binaphthyl stabilized palladium nanoparticles (Pd-BNP) as a reusable catalyst. Less reactive aryl bromides generally provided a similar yield of 3-arylidene-2-oxindoles compared with more reactive aryl iodides. The Pd-BNP nanocatalyst has been recovered and recycled for five catalytic cycles with only an insignificant reduction in particle size, reactivity, and reaction yield.

Multi-component synthesis of fluorophores via catalytic generation of alkynoyl intermediates

This account summarizes recent developments of aggregation-induced emissive and emission solvatochromic fluorophores by multicomponent reactions. Key intermediates are catalytically generated alkynoyl derivatives that are directly transformed into luminophores in a one-pot fashion. The conciseness in combination with ready access to tailored chromophore libraries makes this synthetic methodological concept superior over classical multistep syntheses.

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

Novel triene merocyanines, i.e. 1-styryleth-2-enylidene and 4-(1,3,3-trimethylindolin-2-ylidene)but-2-en-1-ylideneindolones are obtained in good to excellent yields in a consecutive three-component insertion Sonogashira coupling-addition sequence. The selectivity of either series is remarkable and has its origin in the stepwise character of the terminal addition step as shown by extensive computations on the DFT level. All merocyanines display intense absorption bands in solution and the film spectra indicate J-aggregation. While 1-styryleth-2-enylideneindolones show an intense deep red emission in films, 4-(1,3,3-trimethylindolin-2-ylidene)but-2-en-1-ylideneindolones are essentially nonemissive in films or in the solid state. TD-DFT computations rationalize the charge-transfer nature of the characteristic broad long-wavelength absorptions bands.