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.
Lewis acid catalyzed [3 + 2]-cycloaddition reaction of donor-acceptor cyclopropanes with vinyl azides has been developed to obtain diastereomerically enriched azidocyclopentane derivatives. In addition, thermal chemoselective ring expansion of azidocyclopentanes to tetrahydropyridine derivatives and further diastereospecific reduction to a substituted piperidine derivative, with an excellent yield, was also achieved.
In this report, a facile synthesis of tetrahydropyridazines via a Lewis acid catalyzed annulation reaction of cyclopropane carbaldehydes and aryl hydrazines has been demonstrated. Moreover, the generated tetrahydropyridazine further participated in a cycloaddition reaction with donor-acceptor cyclopropanes to furnish hexahydropyrrolo[1,2- b]pyridazines. We also performed these two steps in one pot in a consecutive manner. In addition, a monodecarboxylation reaction of hexahydropyrrolo[1,2- b]pyridazine was achieved with a good yield.
Molnupiravir (MK-4482, EIDD-2801) is an experimental drug that has been demonstrated to be effective for the treatment of COVID-19 in human clinical trials. Herein, we report a concise synthesis of the drug via a novel thionated derivative that relies on one-pot methodologies, thus decreasing the number of purification steps required. This route provides the drug in an overall 62% yield and >99% purity and uses cheap and readily available bulk chemicals, thereby providing an affordable synthesis of the drug for cheaper and wider global accessibility.
Owing to their intrinsic ring strain and ease of synthesis, small carbo- and heterocycles became versatile building blocks. However, the traditional approaches of heterocycle synthesis involved the combination of one...
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