Recent developments on ultrasound assisted catalyst-free organic synthesis

Mother Nature needs to be protected from ever increasing chemical pollutions associated with synthetic organic processes. The fundamental challenge for today's methodologists is to make their protocols more environmentally benign and sustainable by avoiding the extensive use of hazardous reagents and solvents, harsh reaction conditions, and toxic metal catalysts. However, the people of the twenty-first century are well aware about the side effects of those hazardous substances used and generated by the chemical processes. As a result, the last decade has seen a tremendous outburst in modifying chemical processes to make them 'sustainable' for the betterment of our environment. Catalysts play a crucial role in organic synthesis and thus they find huge applications and uses. Scientists' continuously trying to modify the catalysts to reduce their toxicity level, but the most benign way is to design an organic reaction without catalyst(s), if possible. It is worthy to mention that the involvement of ultrasound in organic synthesis is sometimes fulfilling this goal. In many occasions the applications of ultrasound can avoid the use of catalysts in organic reactions. Such beneficial features as a whole have motivated the organic chemists to apply ultrasonic irradiation in more heights and as a results, in recent past, there were immense applications of ultrasound in organic reactions for the synthesis of diverse organic scaffolds under catalyst-free condition. The present review summarizes the latest developments on ultrasound assisted catalyst-free organic synthesis reported so far.

Al(H2PO4)3 as an efficient and recyclable catalyst for the one-pot synthesis of naphthopyranopyrimidines

An efficient one-pot protocol has been developed for the synthesis of naphthopyranopyrimidine derivatives via a three-component reaction of aromatic aldehydes, β-naphthol and 6-amino-1,3-dimethyl uracil in the presence of Al(H₂PO₄)₃.

Preparation of Newα-Aminophosphonate Derivatives by Kabachnik-Fields Reaction Using a Recyclable Catalyst

A convenient and efficient synthetic method for the preparation of some newα-aminophosphonate derivatives via a one-pot three-component system has been achieved using Amberlite IRC-748 as a recyclable catalyst. This method not only provides an excellent complement for the synthesis ofα-aminophosphonates but also avoids the use of hazardous acids or expensive/toxic Lewis acids and harsh reaction conditions. Most of the synthesized compounds (4a–o) exhibited activity against bacteria/fungi strains and moderate DPPH radical scavenging activity.