Donor-Acceptor Cyclopropanes as an Expedient Building Block Towards the Construction of Nitrogen-Containing Molecules: An Update

Nitrogen-containing molecules are the key structural constituent of many pharmaceutical compounds that play a pivotal role in drug development. Owing to their multifaceted medicinal importance, several synthetic approaches have been delineated in the recent past for their construction. Over the past few decades the augmented use of donor-acceptor cyclopropanes (DACs) as three-carbon synthetic equivalents, despite their ring strain, for the construction of innumerable hetero- and carbocycles of pharmaceutical importance has raised the interest of synthetic chemists to this topic. Owing to their zwitterionic nature due to the vicinal disposition of donor and acceptor groups, they have been frequently used in ring-opening reactions, cycloadditions, and rearrangements. This review is mainly focused on assorted reactions of DACs with various nitrogen-containing dipolarophiles like imines, azides, cyanates, isothiocyanates, nitrosocarbonyls, hydrazines, diaziridines, triazinanes, diazenes, etc. towards the synthesis of nitrogen-containing molecules of pharmaceutical and industrial importance. This review is in continuation of our review published in the Israel Journal of Chemistry in April 2016, and includes the literature from April 2016 to May 2019.