Abstract
1,3-Dipolar cycloaddition of 2-diazopropane 2 to conjugateddi-substituted alkenes1 is taking place regiospecifically to give five membered heterocyclic ring 3. The oxidation of 2-pyrazolines 3a,b with dimethylsulfoxide and oxalyl chloride under Swern conditions led to a pyrazolenines 5a,b.