Thia-Michael Reaction under Heterogeneous Catalysis

Thia-Michael reactions between aliphatic and aromatic thiols and various Michael acceptors were performed under environmentally-friendly solvent-free conditions using Amberlyst® A21 as a recyclable heterogeneous catalyst to efficiently obtain the corresponding adducts in high yields. Ethyl acrylate was the main acceptor used, although others such as acrylamide, linear, and cyclic enones were also utilized successfully. Bifunctional Michael donor, 3-mercaptopropanoic acid, positively furnished the product, albeit in a lower yield and after leaving the reaction to take place for a longer time. The catalyst was easy and safe to handle and successfully recycled for five consecutive cycles.

Cooperative catalysis with block copolymer micelles: a combinatorial approach

A rapid approach to identifying complementary catalytic groups using combinations of functional polymers is presented. Amphiphilic polymers with "clickable" hydrophobic blocks were used to create a library of functional polymers, each bearing a single functionality. The polymers were combined in water, yielding mixed micelles. As the functional groups were colocalized in the hydrophobic microphase, they could act cooperatively, giving rise to new modes of catalysis. The multipolymer "clumps" were screened for catalytic activity, both in the presence and absence of metal ions. A number of catalyst candidates were identified across a wide range of model reaction types. One of the catalytic systems discovered was used to perform a number of preparative-scale syntheses. Our approach provides easy access to a range of enzyme-inspired cooperative catalysts.

Synthesis and odor evaluation of five new sulfur-containing ester flavor compounds from 4-ethyloctanoic acid

Five sulfur-containing flavor compounds were synthesized for the first time by the reaction of 4-ethyloctanoyl chloride with sulfur-containing alcohols or mercaptans. The synthesized compounds are 3-(methylthio)propyl 4-ethyloctanoate, 2-methyl-3-tetrahydro-furanthiol 4-ethyloctanoate, 4-methyl-5-thiazoleethanol 4-ethyloctanoate, 2-furan-methanethiol 4-ethyloctanoate and 2-methyl-3-furanthiol 4-ethyloctanoate. These five synthetic sulfur-containing ester flavor compounds all have meaty odor and might be used in foods if approved for this purpose in the future.

Recyclable nanostructured catalytic systems in modern environmentally friendly organic synthesis

Modern chemical synthesis makes heavy use of different types of catalytic systems: homogeneous, heterogeneous and nano-sized. The latter--nano-sized catalysts--have given rise in the 21st century to a rapidly developing area of research encompassing several prospects and opportunities for new technologies. Catalytic reactions ensure high regio- and stereoselectivity of chemical transformations, as well as better yields and milder reaction conditions. In recent years several novel catalytic systems were developed for selective formation of carbon-heteroatom and carbon-carbon bonds. This review presents the achievements of our team in our studies on various types of catalysts containing metal nanoparticles: palladium-containing diblock copolymer micelles; soluble palladium-containing polymers; metallides on a support; polymeric metal salts and oxides; and, in addition, metal-free organic catalysts based on soluble polymers acting as nanoreactors. Representative examples are given and discussed in light of possible applications to solve important problems in modern organic synthesis.