Traditional synthesis methods, assisted

Figure 5.1 Examples of traditional synthesis methods assisted by "green sources" (microwave and ultrasound) of energy in the synthesis of perovskite ABOj-type oxides.

In critical synthesis, ultrasonic assistance is needed to meet the high requirements for temperature and pressure. For instance, in Bischler cyclization, the most traditional synthetic methods for quinazoUne derivatives, high temperature... 

Li et al. (2009) have studied the synthesis of alkyl ferulates under microwave inadiatioa They observed the reactions time ranged from 3-5 min, which was much shorter than the traditional synthetic methods, as well as the alkyl ferulates were obtained in higher yields. It was the first time, when they have reported an efficient microwave-assisted esterification of ferulic acid with alcohols. 

Since the experimental conditions for the traditional Biginelli reaction are quite straightforward, small libraries of DHPMs are readily accessible by parallel synthesis. Along these lines the generation of a 140-member single compound DHPM library by combination of 25 aldehydes, 6 ureas/thioureas, and 7 acetoacetates or acetoamides under standard reaction conditions has been reported [123, 124]. More rapid approaches make use of microwave-enhanced solution-phase protocols [88, 89, 125]. Apart from these conventional solution-phase methods, it is also possible to employ polymer-supported reagents to aid in the purification and workup protocol. Polymer-assisted solution-phase chemistry using polymer-supported... 

In a word, ion-exchange with the assistance of microwaves is feasible, convenient, and fast. It can reach a higher exchange degree than can traditional methods and make the inaccessible ions in traditional methods exchangeable. This method is especially appropriate for the laboratory preparation of ion-exchanged zeolite molecular sieves. The microwave technique is very successful in the synthesis of microporous crystals, modification of the properties of zeolites, secondary synthesis of microporous materials, and the preparation of ultra-fine particles and films, and has attracted the wide interest of chemists in the field of molecular sieves. 

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