Current Organic Synthesis - Volume 5, Issue 4, 2008

The paper presents recent work conducted in our group on the synthesis of a novel class of homogeneous and immobilized Rucomplexes containing Schiff bases as O,N-bidentate ligands benefiting from a versatile, quite general and thoroughly exemplified twostep procedure. The new Ru-complexes with improved stability incorporate a variety of Schiff bases, associated with traditional inorganic and organic ligands such as chloride, phosphanes, arenes, cyclodienes, NHC etc., and different carbenes (alkylidene, vinylidene, allenylidene and indenylidene). By a proper choice of the Schiff base, useful physical and chemical properties of the derived Rucomplexes could be induced resulting in tunable catalytic activity for metathesis and related processes. A pertinent example is the latency of selected Schiff base Ru catalysts which by becoming active only under specific conditions (heat or acid activation) are ideal for industrial applications, e.g. reaction injection molding processes. The synthetic approaches that are critically discussed in this artcile have led to a diversity of Ru-complexes of which several members have risen to the rank of commercial catalysts.

Chiral sulfur ligands which have been developed quite recently bu us are reviewed. Several types of chiral sulfur ligands, which involve a chiral sulfoxide group as a sole chiral source, and other coordinating elements such as phosphine, nitrogen, oxygen, sulfur, and so on, have been developed. A role of the chiral sulfoxide functions as ligands in metal-catalyzed asymmetric synthesis has been revealed by the X-ray crystallographic analysis of the intermediary metal complexes.

Recent advances in the development of environmentally benign solid acid-catalyzed Friedel-Crafts reactions are reviewed. The work includes two main chapters, alkylations and acylations. The data are summarized based on the chemical nature of the reagents used, such as alkenes, alkyl halides and alcohols/ethers in alkylation, while activated carboxylic acid derivatives and carboxylic acids in acylation. Special topics in both major chapters, such as hydroxyalkylation, cyclialkylation, cycliacylation and rearrangements are also discussed.

The utility of ruthenium-based catalysts in the construction of furan and pyrrole derivatives is reviewed. Among others, synthetic approaches involving cycloisomerization, ring-closing metathesis and multicomponent reactions are discussed.

In this review reactivity of uracil and its derivatives towards nucleophilic and electrophilic reagents is described. A different approach of uracil derivatives preparation and their application in further synthesis is also mentioned.