|Microwave-Assisted Rapid Access to Bio-active Heterocycles |
Vivek Polshettiwar and Rajender S. Varma
Environmentally benign protocols have been developed for the synthesis of various pharmaceutically active heterocycles namely 1,3,4-oxadiazoles, 1,3,4-thiadiazoles, 1,3-dioxanes, pyrazoles, hydrazones and 3,4-dihydropyrimidin-2(1H)-ones, which proceed under the influence of microwave irradiation and using eco-friendly conditions. These greener protocols were catalyzed efficiently by solid supported Nafion®NR50, phosphorus pentasulfide on alumina under solvent-free conditions.
|New Accessories for High Throughput and Combinatorial Approach in a Microwave Batch Reactor|
Alexander Stadler, Thomas Karner, Matthias Treu
A unique sealable well-plate system is introduced allowing screening reactions in a 8x6 well format with operation limits of 200°C and 20 bar and a reaction volume of 0.3 mL per well. An appropriate turntable enables to proceed up to 4 of these SiC well plates in one run resulting in 192 parallel reactions at a time. Reaction control is achieved by sensing the IR temperature of the plate surface.
|Microwave Accelerated Heterogeneous Catalysis – Flow-Through Reactor Concept and Application|
T. Glasnov, K. Mennecke, R. Cecillia, U. Kunz, A. Kirschning and C.O. Kappe,
Flow-through processes in organic synthesis become more important as an enabling technology for a cost effective and convenient method. This requires appropriate reactors with functionalities for organic reactions. In this project noble metal-loaded polymer/carrier reactors able to be operated in a microwave field were investigated. By application of a microwave field metal sites are heated whereas the polymer/carrier material remains transparent to irradiation.
|Phase Tranformation of Sodium Carbonate to Monohydrate|
A. Shaikh, A.D. Salman, S. Mcnamara, G, Littlewood and M.J. Hounslow
Sodium carbonate is the most widely used chemical compound in the world. The 50% of this used in glass industry is in the form of dense sodium carbonate. The process of transformation of sodium carbonate to sodium carbonate monohydrate is the key step in the production of dense sodium carbonate. In this present work systematic experiments were conducted by using online in-situ measurement techniques. It is shown that the kinetics of phase transformation process is highly temperature dependant.
|Synthesis of 4,5-dihydroisoxazoles from N-nitroso-4,5 dihydropyrazoles under Microwave Irradiation|
Kostikov R.R., Stepakov A.V., Galkin I.A and Molchanov A.P.
4,5-Dihydroisoxazoles have been used as key intermediates in the synthesis of a bioactive molecules and are found in pharmaceutical agents such as glycoprotein IIb/IIIa (GPIIb/IIIa) inhibitors and human leukocyte elastase inhibitors. In the present work 4,5-dihydroisoxazoles have been prepared by thermal removal of nitrogen from N-nitroso-4,5-dihydropyrazoles under microwave irradiation.
|The Effect of Microwave Irradiation Towards Carbodiimide-Mediated Esterifications on Solid Phase|
Alexander Stadler and Oliver Kappe
A number of publications have reported the coupling of carboxylic acids to Merrifield resin via the cesium salt method and the esterification of Wang resin using carbodiimide either via the isourea method or the symmetrical anhydride method. Reaction times using conventional conditions have been reported to be rather long so we have investigated the effects of microwave irradiation towards both of these reactions using benzoic acid derivatives.
|Rapid Scaffold Decoration of Dihydropyrimidine Derivatives by Microwave-Assisted Solution Phase Synthesis|
Doris Dallinger, Alenka Lengar, Bogdan Khanetskyy, Bimbisar Desai and C. Oliver Kappe
In recent work we have reported the generation of a diverse library of DHPMs, employing an automated, sequential microwave-assisted solution phase strategy. We now present the high-speed microwave scaffold decoration around the DHPM heterocyclic core exploiting the diversity on at least six positions.
|Microwave-Assisted Organic Synthesis in Near-Critical Water at 300°C. A Proof-of-Concept Study|
Jennifer M. Kremsner and C. Oliver Kappe
Microwave-assisted organic synthesis in near-critical water (NCW) in the 270-300 °C temperature range has been investigated in a dedicated multimode microwave reactor utilizing heavy-walled quartz reaction vessels.
Several different known transformations such as the hydrolysis of esters or amides, the hydration of alkynes, Diels-Alder cycloadditions, pinacol rearrangements, and the Fischer indole synthesis were successfully performed in microwave-generated NCW without the addition of an acid
|Microwave-Promoted Hetero-Diels-Alder Reactions of 2(1H)-Pyrazinones in Ionic Liquid Doped Solvents and on Solid Support|
Nadya Kaval, Erik Van der Eycken and C. Oliver Kappe
The readily available and broadly functionalized 2-azadiene system of the 2(1H)-pyrazinones easily undergo inter- and intramolecular Diels-Alder reactions with a wide range of dienophiles providing convenient routes to specifically substituted heterocycles. The reactions in this series are known to be rather sluggish, requiring long reaction times, high temperatures and even sometimes high pressures. Since speed is generally recognized as an important factor in high-throughput synthesis, we have