Ultrasound-promoted synthesis of novel spirooxindolo/spiroacenaphthen dicyano pyrrolidines and pyrrolizidines through regioselective azomethine ylide cycloaddition reaction

Novel dicyano functionalised spiropyrrolidine and spiropyrrolizidine were synthesized from the reaction of various arylidenemalononitrile Knöevenagel adducts with non-stabilized azomethine ylides generated from isatin/acenaphthenequinone and sarcosine/N-phenylglycine/proline. The reactions were carried out under both conventional heating and ultrasonic irradiation conditions. In general, improvement in rates and yields were observed when the reactions were carried out under sonication compared with classical conditions. The regio and stereochemistry of the products was established by single crystal X-ray structure and spectroscopic techniques.