Chemodivergent Hydrazinolysis of Donor-Acceptor Cyclopropanes: Approach to Hexahydropyridazin-3-ones and 1-Aminopyrrolidin-2-оnes

A divergent synthesis of substituted hexahydropyridazin-3-ones and 1-aminopyrrolidin-2-ones has been achieved through domino ring opening/ring closure reactions of donor–acceptor cyclopropanes with ambident, unsymmetrically substituted hydrazines, affording target products in good yields under mild conditions. The selectivity of this process depends strongly on the nature of substituents in hydrazine. Aryl hydrazines bearing electron-rich and electron-neutral aromatic groups form six-membered rings by attacking the cyclopropane via the NH group, while the NH2 group reacts in hydrazines equipped with electron-withdrawing aromatic substituents, acyl hydrazines, and carbazates. In both scenarios, the initial products of nucleophilic ring opening undergo in situ Lewis acid-induced cyclization, providing important azaheterocyclic systems in a single synthetic step; further transformations enable access to other valuable products. The proposed mechanism of the title process and the observed chemoselectivity switch have been explained by both experimental and computational studies.