Reactions of spirocyclopropane-containing 1-and 2-pyrazolines with electrophilic reagents

Hydrochlorination of spiro(1-pyrazoline-3,1'-cyclopropanes) proceeds regios electively at the azocyclopropane group to form 3-(2-haloethyl)pyrazoline d erivatives. If the latter contain a halogen atom in the heterocycle, they a re readily converted into (2-haloethyl)pyrazole hydrohalides. Bromination o f 3-cyanospiro(2-pyrazoline-5,1'-cyclopropane) with N-bromosuccinimide at 2 0 degrees C proceeds with retention of the cyclopropane ring to form 3-brom o-3-cyanospiro(1-pyrazoline-5,1'-cyclopropane), which is converted into (2- bromoethyl)cyanopyrazole in similar to 60% yield at similar to 20 degrees C after 3-4 days.