Electrochemical electrophilic bromination/spirocyclization of N-benzyl-acrylamides to brominated 2-azaspiro[4.5]decanes

Abstract

An electrochemical electrophilic bromination/spirocyclization of N-benzyl-acrylamides with 2-bromoethan-1-ol as the brominating reagent has been developed. The paired electrolysis employs low concentrations of bromine produced from both cathodic reduction and anodic oxidation as an electrophile, and realizes an H₂O-involved electrophilic spirocyclization. A number of unexplored brominated 2-azaspiro[4.5]decanes are obtained with satisfactory yields under mild conditions, and the reaction exhibits good efficiency at the gram-scale synthesis. In addition, this approach is further highlighted by late-stage transformations and synthetic applications in constructing cyclohepta[c]pyrrole-1,6-diones via debromination tandem cyclization of brominated 2-azaspiro[4.5]decanes.