Catalyst-Free One-Pot Regioselective Synthesis of Spiropyrrolizines Using 1,3-Dipolar Cycloaddition Reaction

Synthesis of functionalized spiro[acenaphthylene-1,3 '-pyrrolizin]-2-ones and spiroindeno[1,2-b]quinoxaline-11,3 '-pyrrolizines has been reported by one-pot condensation of active carbonyl compounds, L-proline/L-thioproline and 3-methyl-4-nitro-5-styrylisoxazoles in MeOH under reflux. This multicomponent strategy afforded corresponding spiro products in 94-98% yield with high diastereo- and regioselectivity. The structure has been further confirmed by X-ray analysis of single crystal of one of the compounds. The striking feature of this work is avoidance of usage of toxic catalysts for this one-pot synthesis.