Site-selective ring opening of bicyclo[n.1.0]alkanols: an Fe(ii)-catalyzed 1,6-conjugate addition to p-quinone methides

Abstract

Herein, we report an efficient synthetic strategy for an Fe(II)-catalyzed site-selective ring opening of bicyclo[n.1.0]alkanols and their concomitant 1,6-conjugate addition to p-quinone methides. Access to tertiary carbon centers with appendaged...

Iron-Catalyzed Oxidative Rearrangement of Cyclopropanone Hemiaminals: General Access to Pyrroloindolones from Indoles

“…When starting from bicyclic cis -fused analogue 2p instead, a trans -fused pyrroloindolone 3p was isolated as a single diastereomer, again consistent with such a β-carboxylic radical intermediate capable of epimerization prior to cyclization. Based on this evidence and the previously documented reactivity of cyclopropanols in oxidative conditions, ,, a plausible mechanism for the Fe­(III)-catalyzed oxidative rearrangement developed is presented in Scheme . Following ligand substitution with the cyclopropanone hemiaminal 2a – 2p to produce an iron alkoxide intermediate, fragmentation via homolysis of the Fe­(III)–O bond generates an Fe­(II) species and a β-carboxylic radical likely stabilized via equilibrium to its cyclopropyloxy radical form .…”

“…Inspired by the ring-opening functionalization of analogous cyclopropanols, , we then looked at alternative metal sources as catalysts (entries 12–15). To our delight, the use of Fe­(III) catalysts led to a notable increase in reaction efficiency, with inexpensive Fe­(acac) 3 affording 82% NMR yield (entry 15). Evaluation of different other temperatures, concentrations and solvent ratios did not lead to further improvement in yield .…”