Green synthesis scopes

Figure 8.4 Battery of metrics for assessment of the material greenness of synthesis reactions. Left The assessment (and optimization) involves two dimensions that require different metrics. Right Scope and hierarchy of the metrics.

Numerous useful organic transformations are known to be accelerated by US irradiation [51]. Compared to traditional methods, US-promoted methodologies are of more convenience and share many common features with other green chemical techniques [52]. An US-enhanced synthesis of 1,5-benzodiazepines (Scheme 12) catalyzed by p-toluenesulfonic acid (p-TSA) has been reported [53]. A variety of catalysts such as silica, Amberlyst 15, Dowef, K-10, ZnCl2, and so on were screened, but p-TSA was foxmd to be the best in terms of yield. The scope and limitation of the method was studied and it was foxmd that the reaction was unsuccessful with aryl alkyl ketones, a,(3-unsaturated ketones, and cyclic ketones. 

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