Chiral 1,2-diamines are privileged structural motifs in organocatalysis, whereas efficient 1,3-diamine-derived organocatalysts are very rare. Herein, a highly efficient camphor-1,3-diamine-derived squaramide organocatalyst is reported. Its catalytic activity in Michael additions of 1,3-dicarbonyl nucleophiles to trans-beta-nitrostyrene derivatives provides excellent enantioselectivities (up to )99% ee). Notably, the catalyst's performance is excellent also in aqueous medium and it is not sensitive to air. The results published in this article represent an important breakthrough of the programme group and provided a solid foundation for further development of the research programme in the field of organocatalysts.
Rhodium-catalyzed intramolecular C–H insertion with diazo compounds, which are tethered by alkoxyamines, afforded 1,5- and the rare 1,7-insertion products (see scheme; Bn=benzyl). The resulting N–O tether is unaffected under the C–H insertion reaction conditions and it can be readily cleaved or transformed into various functionalities. The reduction of the N–O moiety controls acyclic stereochemistry. Selectivity control is of fundamental importance for a successful transformation. In this paper, a controlled intramolecular cyclative insertion of a carbenoid, formed from alpha-diazohydroxamates, into a c–H bond of the substrate. This article belongs to the field of metal-catalyzed C–H activation, which is a vital part of the programme.
Hydrogenation of prochiral ketones using chiral transition-metal catalysts represents the cleanest way to access enantiomerically enriched secondary alcohols, which are important building blocks in fine chemicals synthesis. Despite excellent activity, selectivity and compatibility of metal complexes with variety of functional groups, no universal catalysts exist. In this article we summarize the advances in catalyst systems for the asymmetric homogenous and heterogenous hydrogenation of ketones that have been made in past decade. The development of catalysts is oriented in reaching as high as activity with low catalyst loadings, using “greener’’ conditions, and ensuring good recyclability of catalysts. Even though ruthenium complexes represent the largest part of the catalysts, other metals rapidly penetrate this field. Review paper on advanced method for the synthesis of enantiomerically pure alcohols. The paper belongs to the filed of asymmetric catalysis, which is a vital part of the programme.
The one-pot synthesis of a broad variety of dihydrofuroquinolines, dihydrothienoquinolines, and dihydrobenzoquinolines is reported. The combination of the Rh(I)-catalyzed hydroarylation of vinylpyridines with the Pd(0)/Pd(II)-catalyzed direct C–H arylation in a Multicomponent-Multicatalyst Reaction (MC)2R could be used to develop an efficient and step-economic protocol for the rapid construction of molecular complexity. A high-yielding synthesis of ?-extended heteroarenes through an efficient three-step-one-pot procedure and a highly enantioselective synthesis of 6-alkylsubstituted dihydrobenzoquinolines are shown. Metal-catalyzed C-H arylation is the core research field of our programme.
Heteroaromatics bearing unprotected hydroxyalkyl functions can be arylated using aryl or heteroaryl bromides, via palladium-catalysed carbon-hydrogen bond activation/arylation. Good yields were generally obtained using 0.01–0.5 mol% of the air-stable palladium acetate complex as the catalyst. The nature of the base was found to be crucial for the selectivity of this reaction. Potassium acetate led to the direct arylation products whereas caesium carbonate led to the formation of the ether. This procedure is certainly more atom-economic than other methods for the preparation of such compounds, as no protection/deprotection sequence of the hydroxyalkyl function and no preparation of an organometallic derivative is required. Metal-catalyzed C-H arylation is the core research field of our programme.
The synthesis, characterization and (TD)-DFT calculations of the electrochemical and photophysical properties of novel ethynylene-analogues of hemicurcuminoids are described. These dyes are both emissive in solution and in the solid state. While compounds that emit through an efficient charge transfer (CT) state show solvatochromic behaviour associated with low fluorescence quantum yields, those lacking of donor groups show high fluorescence quantum yields of 70–80%, in solution. The latter dyes also present the advantage to emit in the solid state in the visible region with fluorescence quantum yields up to 23%. Their condensed phase spectrum can be bathochromically shifted to the near infrared region (742 nm) by appending a strong donor group. New fluorescent probes and their properties are important topic of the programme.
Racemic ?2-pyrrolin-4-ones (4-pyrrolones), easily available in two steps from N-protected ?-amino acids, undergo organocatalysed asymmetric Mannich-type addition to isatin-derived ketimines to furnish the non-racemic oxindole- ?2-pyrrolin-4-one adducts, stereoselectively (up to 96% ee, dr 15:1). The oxindole–pyrrolone products feature vicinal tetrasubstituted carbon stereocenters.The developed protocol has a broad substrate scope and tolerates diverse substituents at position C-5 in 4-pyrrolones and at positions N-1 and C-5/7 in isatin imines. Efficient asymmetric catalytis methods for simultaneous C-C bond formation and construction of two stereogenic centers are rare, therefore, the developed method is an important contribution to the field of asymmetric organic synthesis, (organo)catalysis, and stereochemistry. Important results related to the topic of the proposed programme.
A series of hexa(heteroaryl)benzenes were synthesized by the Ru(II)-carboxylate-catalyzed multiple C-H activation of benzenes carrying pyridyl, pyrimidyl, or pyrazolyl directing groups using N-heteroaryl bromides as coupling partners. The reactions proceeded with high selectivity under microwave irradiation in water. Iterative pentaarylation could be implemented via activation of C-H bonds of generated intermediates by cascade chelation assistance of in situ installed pyridyl groups. This strategy provides multidentate ligands for selective complexation of transition metals and potential building of photoredox systems. Important breakthrough of the programme group in the filed of C-H activation.
A series of 16 copper metal-catalyzed CuAIAC reactions between four pyrazolidinone-1-azomethine imines and four terminal ynones gave the corresponding fluorescent cycloadducts as bimane analogues in very high yields. Applicability of CuAIAC was demonstrated by fluorescent labelling of functionalized polystyrene and by using Cu–C and Cu–Fe as catalysts. Experimental evidence, kinetic measurements and correlation between a clean catalyst surface and the reaction rate are in agreement with homotopic catalytic system with catalytic Cu(I)-acetylide formed from Cu(0) by 'in situ' oxidation. Availability of azomethine imines, mild reaction conditions, simple workup, and scalability make CuAIAC a viable supplement to CuAAC reaction in 'click' chemistry.
Efficient diarylation of ortho-C-H bonds of 2-arylpyrimidines was achieved by Ru(II)-carboxylate-catalyzed reaction with aryl bromides in water, whereas meta-substituted phenylpyrimidines selectively led to monoarylation. The reaction is strongly accelerated under microwave irradiation, and is compatible with various functional groups on both coupling partners. As established from Hammett plots, electron-withdrawing groups on the pyrimidine substrates facilitate the arylation, while both, electron-withdrawing and electron-donating groups on the aryl bromides lead to a faster reaction. The C-H functionalization of 2-arylpyrimidines with heteroaryl halides provides potential multidentate ligands. This article belongs to the field of metal-catalyzed C–H activation and direct (hetero)arylation, which are vital parts of the programme.