A convenient approach for the synthesis of various derivatives of pyrazolo[1,2-b]phthalazinediones in the presence of an efficient supported basic ionic liquid at ambient temperature and solvent-free media

Nitrogen-bridgehead compounds: overview, synthesis, and outlook on applications

The nitrogen-bridgehead is a common structural motif present in a multitude of natural products. As many of these abundant compounds exhibit biological activities, e.g. against cancer or bacteria, these derivatives are of high interest. While natural products are often associated with problematic characteristics, such as elaborate separation processes, high molecular complexity and limited room for derivatization, purely synthetic approaches can overcome these challenges. Many synthetic procedures have been reported for preparation of artificial nitrogen bridgehead compounds, however, to our surprise only a fraction of these has been tested for their bioactivity. This review is therefore meant to give an overview of existing synthetic methods that provide scaffolds containing bridgehead nitrogen atoms, covering the period from 2000 to 2023. Reviews which cover subunits of this topic are referenced as well.

Unexpected synthesis of 4-(4,5-dihydro-1H-imidazol-2-ylsulfanyl)butyl-H-sulfite as a catalyst for the synthesis of pyrazolophthalazines

Several attempts for preparation of 4,4'-(2-thioxoimidazolidine-1,3-diyl)bis(butane-1-sulfonic acid) were not successful despite taking 2 mmol of 1,4-butane sultone in reaction with 1 mmol of imidazolidine-2-thione. Instead, 4-(4,5-dihydro-1H-imidazol-2-ylsulfanyl)butyl hydrogen sulfite (DISBHS) was prepared unexpectedly, characterized and used for the synthesis of diverse pyrazolophthalazines from the one-pot three component condensation reaction of phthalhydrazide, malononitrile and aldehydes under mild conditions.