Transition metal oxide nanopowder and ionic liquid: an efficient system for the synthesis of diorganyl selenides, selenocysteine and derivatives

Abstract

Neste trabalho foi desenvolvido um método eficiente para a síntese de selenetos de diorganoíla e β-seleno aminas empregando Zn, quantidades catalíticas de ZnO nanoestruturado e líquidos iônicos (LI) como solventes recicláveis. Este sistema ZnO/LI apresentou alta eficiência nesta transformação, levando à formação dos produtos desejados em bons rendimentos.We have developed an efficient method for the synthesis of diorganyl selenides and β-seleno amines using Zn, catalytic amounts of ZnO nanopowder, as a catalyst and ionic liquid as a recyclable solvent. This ZnO/ionic liquid system shows high efficiency in catalyzing these transformations with the formation of the desired products in high yields. Keywords: synthesis, nanocatalysis, ionic liquids, selenium, selenocysteine, selenides IntroductionThe attention gained by organoselenides has been driven by the potential applications of selenium compounds in modern organic syntheses and asymmetric catalysis. 1,2 Their importance stems from the prevalence of C-Se bonds in compounds with biological and pharmaceutical impact, e.g., selenocarbo-hydrates, 3 selenoamino acids 4 and selenopeptides. 5 This class of molecules performs multiple therapeutic functions of great importance, for example, in antiviral to anticancer agents and in a variety of situations where free radicals are involved. 6 Organoselenium compounds are important synthetic intermediates, and the formation of symmetrical and unsymmetrical diorganyl selenides is an area of intense research. In general, diselenide bond cleavage is carried out employing common reducing agents and expensive metal sources, as depicted in Scheme 1. 7,8 Furthermore, reductive cleavage achieved by CsOH, 7 ArB(OH) 2 /CuI 8 and photochemical reactions 7 has been reported in a substantial number of previous studies.Reactions catalyzed by transition metal complexes have made a great contribution to the recent advances in relation to the cross-coupling reactions of diaryl diselenides with aryl halides. [9][10][11][12] However, most of the methods available to synthesize diorganyl selenides have serious disadvantages including: i) the use of expensive metal sources and J. Braz. Chem. Soc. 2080 reagents such as La, Yb, In, InI, and SmI 2, etc.; ii) handling difficulties; iii) functional group incompatibility; iv) difficult work-up procedures; v) harsh reaction conditions, such as the use of strong acids or bases and vi) high temperatures or long reaction times. Thus, there is still considerable interest in the development of highly efficient methods for this transformation. 13 Designing new specific catalysts and exploring their catalytic activity can have significant effects on optimizing the efficiency of a wide range of organic synthesis techniques, and has resulted in more economical and environmentally-friendly chemical processes through the replacement of nonselective, unstable or expensive catalysts.Nanotechnology is an emerging approach towards synthetic organic chemistry, particularly the area of nano-catalyzed organic tra...

A mild and efficient procedure for alkenols oxyselenocyclization by using ionic liquids

“…Potewar et al described the condensation of selenourea with different phenacyl bromides employing mixtures of different alkylimidazolium ILs with water . Different groups prepared diorganyl selenides and selenolesters in a series of dialkylimidazolium ILs employing different promoters and catalysts as Zn dust, ZnO nanopowder, CuO nanopowder, NaBF 4 , Indium and InI, triphenyl phosphine, palladium, or the bimetallic reagent Sn(II)/Cu(II) . The use of [bmim][BF 4 ] and [bmim][PF 6 ] in the synthesis of diaryl selenides by electrophilic substitution in arylboron reagents with phenylselenyl halides has been also described .…”

A Straightforward and High-Yielding Synthesis of 1,2,4-Oxadiazoles from Chiral N-Protected α-Amino Acids and Amidoximes in Acetone-Water: An Eco-Friendly Approach

“…As part of our growing interest in using α-amino acids as chiral building blocks in organic synthesis [21,[38][39][40][41][42][43][44][45] and in connection with the increasing importance of the synthesis of small libraries of compounds with programmed variations of substituents, we describe herein an assay, an inexpensive synthetic route for the preparation of a set of chiral Nprotected α-amino acids-derived 1,2,4-oxadiazoles under microwave irradiation, as depicted in Scheme 1.…”

Novel chiral ionic liquid (CIL) assisted selectivity enhancement to (L)-proline catalyzed asymmetric aldol reactions

“…4,5 Previous studies have shown that in many asymmetric reactions the use of CILs as reaction media or catalyst can enhance the yield and/or selectivity significantly. [6][7][8] As most of the asymmetric reactions were carried out using metal/chiral catalysts as chiral sources, which are relatively expensive or environmental unfriendly, searching for a catalyst which is easy to obtain and environmentally benign for the asymmetric reactions is of great significance. In our previous work, a series of (L)-proline based CILs were proved to have the potential to provide a strong chiral environment by 19 F NMR study.…”