Alexander S. Kucherenko

(1,2-Diaminoethane-1,2-diyl)bis(N-methylpyridinium) Salts as a Prospective Platform for Designing Recyclable Prolinamide-Based Organocatalysts

A new efficient and highly recyclable organocatalyst has been developed for asymmetric cross-aldol reactions under neat conditions in ketone-ketone, ketone-aldehyde, and aldehyde-aldehyde systems. The catalyst features two prolinamide fragments and a C2-symmetrical (1,2-diaminoethane-1,2-diyl)bis(N-methylpyridinium) group. The catalyst retained high activity and excellent stereoselection over the operating period of more than 830 h (25 cycles). An ab initio theoretical investigation explained the absolute configuration of the products and different stereoinduction levels for designed diastereomeric organocatalysts.

Regio-, stereo-, and enantioselective reactions of carbon acids catalyzed by recoverable organic catalysts bearing ionic liquid moieties

Organic compounds bearing specific ionic liquid (IL) moieties, in particular, bulky organic cations and fluorinated organic or inorganic anions, catalyze many important reactions of carbon acids involving carbanions and enols as reactive species, such as aldol, Michael, and dichlorocyclopropanation reactions. Many of these catalysts are at least comparable to traditional phase-transfer catalysts (PTCs) with halide anions or organocatalysts based on amino acid derivatives. Furthermore, they enjoy the advantage of being readily recoverable and hence are available for multiple recycling in chemical reactions.

Green asymmetric synthesis of Warfarin and Coumachlor in pure water catalyzed by quinoline-derived 1,2-diamines

Simple enantiomerically pure C2-symmetric quinoline (isoquinoline)-derived 1,2-diamines were synthesized from the corresponding aldehydes via stereospecific diaza-Cope rearrangement with 2,2′-(1,2-diaminoethane-1,2-diyl)diphenol (HPEN). Efficient green synthesis of both enantiomers of the anticoagulant Warfarin and rodenticide Coumachlor was achieved in an aqueous medium via the asymmetric iminium-type Michael reaction in the presence of the catalysts 8e and (ent)-8e in combination with (R)- or (S)-mandelic acid, respectively. This procedure provides high enantioselectivity (up to 91% ee), which has never been attained for these bioactive compounds with the known catalysts under aqueous conditions. Nearly optically pure Warfarin (∼99% ee) was prepared via a green isolation procedure, which included acidic precipitation of the crude product from a basic aqueous solution followed by single recrystallization. Furthermore, unlike the known primary amine-derived organocatalysts, the developed aqueous catalytic system does not produce parasitic byproducts and can be recovered and reused in the asymmetric reaction.

Novel L-threonine-based ionic liquid supported organocatalyst for asymmetric syn-aldol reaction: activity and recyclability design

A novel recyclable threonine-derived ionic-liquid-supported organocatalyst of asymmetric cross-aldol reactions has been developed. In its presence, aromatic aldehydes react with hydroxyacetone, methoxyacetone and 2-butanone to afford the corresponding syn-aldol products in moderate to high yields with excellent diastereo(syn/anti up to 96:4) and enantio-selectivity (up to 95 % ee), which was retained over five recycling experiments.