The chemistry of cyclopropanes containing both donor and acceptor substituents has recently attracted more and more attention from scientists due to their enormous synthetic potential. Under the action of various acids, the carbon-carbon bond is polarized, which leads to the opening of the cyclopropane ring and a variety of subsequent transformations.
Within the framework of systematic research by the laboratory № 6 of the ZIOC RAS in the field of donor-acceptor cyclopropane chemistry, a process of ionic cyclopropanation was developed based on the addition of diazoesters to donor-acceptor cyclopropanes in the presence of GaCl3 as a Lewis acid. As a result, tetrasubstituted activated cyclopropanes, unusual and promising intermediates of organic synthesis, are formed as the main products. In this work, their reaction with benzaldehyde was carried out, leading to five-membered lactones. As part of the study, the mechanisms of all the discovered transformations were also studied in detail.
Irina A. Borisova, Daria-Maria V. Ratova, Konstantin V. Potapov, Anna V. Tarasova, Roman A. Novikov, Yury V. Tomilov “Cyclopropanation of Cyclopropanes”: GaCl3-Mediated Ionic Cyclopropanation of Donor−Acceptor Cyclopropanes with Diazo Esters as a Route to Tetrasubstituted Activated Cyclopropanes J. Org. Chem., 2021, 86, 4567–4579. DOI: 10.1021/acs.joc.0c02983.