Organic microwave-assisted

Department of Chemistry, Laboratory for Organic Microwave-Assisted Chemistry (LOMAC), Kathoiieke Universiteit Leuven, Celestijneniaan 200F, 3001, Leuven, Belgium e-mail erik.vandereycken chem.kuleuven.be... 

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

The performance of microwave-assisted decomposition of most difficult samples of organic and inorganic natures in combination with the microwave-assisted solution preconcentration is illustrated by sample preparation of carbon-containing matrices followed by atomic spectroscopy determination of noble metals. Microwave-assisted extraction of most dangerous contaminants, in particular, pesticides and polycyclic aromatic hydrocarbons, from soils have been developed and successfully used in combination with polarization fluoroimmunoassay (FPIA) and fluorescence detection. 

This chapter has taken the reader through a number of microwave-assisted methodologies to prepare and further functionalize 2-pyridone containing heterocycles. A survey of inter-, intramolecular-, and pericyclic reactions together with electrophilic, nucleophilic and transition metal mediated methodologies has been exemplified. Still, a number of methods remain to be advanced into microwave-assisted organic synthesis and we hope that the smorgasbord of reactions presented in this chapter will inspire to more successful research in this area. 

A microwave-assisted three-component reaction has been used to prepare a series of 1,4-disubstituted-1,2,3-triazoles with complete control of regiose-lectivity by click chemistry , a fast and efficient approach to novel functionalized compounds using near perfect reactions [76]. In this user-friendly procedure for the copper(l) catalyzed 1,3-dipolar cycloaddition of azides and alkynes, irradiation of an alkyl halide, sodium azide, an alkyne and the Cu(l) catalyst, produced by the comproportionation of Cu(0) and Cu(ll), at 125 °C for 10-15 min, or at 75 °C for certain substrates, generated the organic azide in situ and gave the 1,4-disubstituted regioisomer 43 in 81-93% yield, with no contamination by the 1,5-regioisomer (Scheme 18). 

Kappe CO, Stadler A (2002) Microwave-assisted combinatorial chemistry. In Loupy A (ed) Microwaves in organic synthesis. Whey, Weinheim... 

Fig. 8 Modified Smith process vial for microwave-assisted solid-phase organic synthesis...

Tierney JP, Lidstroem P (eds) Microwave assisted organic synthesis. Blackwell Publishing Ltd, Oxford, UK... 

Swamy KMK, Yeh W-B, Lin M-J, Sun C-M (2003) Curr Med Chem 10 2403 CarUlo JR, Dfaz-Ortiz A, de la Hoz A, Moreno A, Gomez MV, Prieto P, Sanchez-Migalldn A, Vazquez E (2003) In Attanasi OA, Spinelli D (eds) Targets in heterocyclic systems, chemistry and properties. Italian Society of Chemistry, vol 7 Baxendale IR, Lee A-L, Ley SV (2005) In Tierney JP, Lidstrom P (eds) Microwave assisted organic synthesis, chap 6. Blackwell Publishing Ltd, Oxford, UK Kappe CO, Stadler A (2005) Microwaves in organic and medicinal chemistry, chap 7. Wiley, Weinheim... 

Keywords Copper MAOS (Microwave assisted organic synthesis) Nickel Palladium Transition-metal-mediated bond formation... 

LindstrOm P, Tierney JP (eds) (2005) Microwave-assisted organic synthesis. Black-well, Oxford... 

An additional interest in the appUcations of microwave-assisted organic synthesis is related to the possibility of having more rapid access to large libraries of diverse small molecules and heterocycUc compounds... 

Triazoles have been obtained via microwave-assisted [3-i-2] cycloaddition, under solvent-free conditions [54], starting from organic azides and acetylenic amides at 55 °C for 30 min (Scheme 23). The complete conversion of the reagents into AT-substituted-1,2,3-triazoles 69 was achieved without decomposition and side products. A control reaction carried out at the same temperature in an oil bath did not give the cycHc products, not even after 24 h of reaction time. 

HMPB 4-Hydroxymethyl-3-methoxyphenoxybutyric acid MAOS Microwave-assisted organic synthesis NBS AT-Bromosuccinimide NIS AT-Iodosuccinimide PIPE Poly(tetrafluroethylene)... 

Due to the importance of substituted 2-pyridones, many preparative methods have been reported (see Sect. 2.1), and some of these, but for from all, have been further developed into methods suitable for microwave-assisted organic synthesis (MAOS). Here we describe mainly methods performed with instruments specially designed for MAOS, thus excluding synthesis per-... 

Microwave technology has now matured into an established technique in laboratory-scale organic synthesis. In addition, the application of microwave heating in microreactors is currently being investigated in organic synthesis reactions [9-11] and heterogeneous catalysis [12, 13]. However, most examples of microwave-assisted chemistry published until now have been performed on a... 

P. Lindstrom, J. Tierney, B Wathey and J. Westerman, Microwave Assisted Organic Synthesis - A Review , Tetrahedron, 2001, 57, 9222. 

Microwave-assisted extraction (MAE) of analytes from various matrices using organic solvents has been operative since 1986 [128], In this process microwave energy is used to heat solvents in contact with a solid sample uniformly and to partition compounds of analytical interest from the sample matrix into the solvent. The way in which microwaves enhance extraction is not fully understood. The main factors to consider include improved transport properties of molecules, molecular agitation, the heating of solvents above their boiling points and, in some cases, product selectivity. 

Work is in progress to validate the MAE method, proposed for EPA, in a multi-laboratory evaluation study. Nothing similar has been reported for additives in polymeric matrices. Dean el al. [452] have reviewed microwave-assisted solvent extraction in environmental organic analysis. Chee et al. [468] have reported MAE of phthalate esters (DMP, DEP, DAP, DBP, BBP, DEHP) from marine sediments. The focus to date has centred on extractions from solid samples. However, recent experience suggests that MAE may also be important for extractions from liquids. 

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