Amine-promoted three-component cycloaddition of bicyclo[1.1.0]butanes with hydroxylamine and polyformaldehyde: expedient access to 2-oxa-3-azabicyclo[3.1.1]heptanes

The regioselective synthesis of C4-unsubstituted 2-oxa-3-azabicyclo[3.1.1]heptanes was achieved by amine-promoted formal dipolar [4π + 2σ] cycloaddition of bicyclo[1.1.0]butanes with hydroxylamines and polyformaldehyde.