Conventional synthesis technique

To explore its biological properties by various functional tests [94], a substantial amount had to be synthesized. Instead of going for 79 (Scheme 1-19) the more distant compound 80 (Scheme 1-20) was aimed at, by conventional synthesis technique. 

As with PPy, polythiophene can be produced using a chemical oxidant. However, due to the limited solubility of thiophene, this reaction must be carried out in nonaqueous media. Copper (II) perchlorate has been used as an oxidizing agent in acetonitrile to yield a simultaneous polymeriza-tion/doping process. This results in polymer materials with conductivities of approximately 8 S cm T Alternatively, a Grignard reaction can be used (Figure 6.3) to produce polythiophene which is the first time conventional synthesis techniques have been used. 

The most successful application of microwave energy in the preparation of heterogeneous solid catalysts has been the microwave synthesis and modification of zeolites [21, 22], For example, cracking catalysts in the form of uniformly sized Y zeolite crystallites were prepared by microwave irradiation in 10 min, whereas 10-50 h were required by conventional heating techniques. Similarly, ZSM-5 was synthesized in 30 min by use of this technique. The rapid internal heating induced by microwaves not only led to a shorter synthesis time, and high crystallinity, but also enhanced substitution and ion exchange [22]. 

An 8000-member library of trisamino- and aminooxy-l,3,5-triazines has been prepared by use of highly effective, microwave-assisted nucleophilic substitution of polypropylene (PP) or cellulose membrane-bound monochlorotriazines. The key step relied on the microwave-promoted substitution of the chlorine atom in monochlorotriazines (Scheme 12.7) [35]. Whereas the conventional procedure required relatively harsh conditions such as 80 °C for 5 h or very long reaction times (4 days), all substitution reactions were found to proceed within 6 min, with both amines and solutions of cesium salts of phenols, and use of microwave irradiation in a domestic oven under atmospheric reaction conditions. The reactions were conducted by applying a SPOT-synthesis technique [36] on 18 x 26 cm cellulose membranes leading to a spatially addressed parallel assembly of the desired triazines after cleavage with TFA vapor. This concept was later also extended to other halogenated heterocycles, such as 2,4,6-trichloropyrimidine, 4,6-dichloro-5-nitropyrimidine, and 2,6,8-trichloro-7-methylpurine, and applied to the synthesis of macrocyclic peptidomimetics [37]. 

The adoption of PASP synthesis presents the opportunity for in-Une purification strategies, through the use of supported scavengers or reagents and catch-and-release strategies. In this way, conventional purification techniques such as aqueous workups and column chromatography can be eliminated. In addition, the use of PASP synthesis reduces the vast number of traditional synthetic manipulations to a series of repetitive incubations and subsequent filtrations, which are in principle well suited to automated processing. 

Conventionally, SiO thin films are deposited at temperatures exceeding 600°C by thermal CVD. Therefore to enable co-deposition of SiO and parylene thin films in the form of nanocomposites, it was necessary to first develop a near room temperature silica (SiO ) synthesis technique. Desu first demonstrated the possibility of near room temperature deposition... 

The ferroelectric Pb(Mgy3Nb2/3)03 (PMN) ceramic has been the snbject of extensive investigations due to its high dielectric coefficient and high electrostrictive coefficient, which renders it suitable for use in capacitors and electrostrictive actuators. However, the successful exploitation of this material is limited by the difficulty of producing a single-phase material with the perovskite structnre. Conventional solid state synthesis techniques invariably resnlt in the formation of one or more pyrochlore phases, which exhibit poor dielectric properties. 

Ferrite ceramics have found widespread applications as materials for permanent magnets and recording media due to their low cost and attractive magnetic properties. The conventional method for manufacturing ferrite ceramics involves solid state reaction of oxide or carbonate precursors at high temperature. Although technically simple, this method does not readily allow control of the product s microstructure and purity, which is necessary for the attainment of optimal magnetic properties. As a result, there has been considerable research into the development of alternative synthesis techniques. 

All of these external resources have relied heavily on the university as a primary source. An unfortunate consequence of these activities over the past decade has been a depletion of the academic resources that have accumulated over the past 50 years. Furthermore, the availability of useful quantities from current academic research has become less likely as modern chemical techniques and instrumentation permit studies with only a few milligrams. This is especially apparent in the natural product field, as the unique diversity inherent in that group has placed such acquisition at a premium. Market demands, nevertheless, persist and have led to the emergence of synthesis factories that prepare compounds specifically for the screening market, using conventional chemical techniques. Output has been greatly enhanced at some of these centers by adoption of modular approaches in synthesis. These sources have helped to fill the void in numbers, but have done little to enhance the level of structural diversity or the cost factor. 

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