Lewis acid catalyzed reactions of donor-acceptor cyclopropanes with 1-and 2-pyrazolines formation of substituted 2-pyrazolines and 1,2-diazabicyclo[330]octanes

The reaction of 2-substituted cyclopropane-1 1-dicarboxylates with 1- and 2-pyrazolines is efficiently catalyzed by scandium or ytterbium triflates to give N-substituted 2-pyrazolines or 1 2-diazabicyclo 13 3 0]octanes The reactions of 2-pyrazolines give diazabicyclooctanes as the major products In contrast the reactions starting from 1-pyrazolines predominantly give N-substituted 2-pyrazolines which become the major compounds obtained if an equimolar amount of GaCl3 is used A possible reaction mechanism is suggested (C) 2010 Elsevier Ltd All rights reserved