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The stereo/regio/chemoselective syntheses of a library of novel spiro[acenaphthylene-1,3′-pyrrolizin]-2-one and spiro[acenaphthylene-1,5′-pyrrolo[1,2-c]thiazol]-2-one have been achieved through 1,3-dipolar cycloaddition. Intermediate azomethine ylides generated in situ from α-amino acids and acenaphthylene-1,2-dione react with α-aroylidine ketenedithioacetal (AKDTA) derivatives to give the target product in excellent yield under ultrasound irradiation. Further, spiro-S,S-acetals are converted to spiro-2H-pyranones by a one-pot cyclization strategy.

An efficient chemo/regio/stereoselective synthesis of novel and functionalized spiro-oxindole/pyrrolizine/pyrrolidine scaffolds has been achieved. The in situ generated azomethine ylide from isatin & L-proline/phenyl alanine underwent 1,3-dipolar cycloaddition with α-aroylidineketene dithioacetals under simple reaction conditions affording spiro-oxindole derivatives. This protocol exhibits an interesting double bond selectivity of α-aroylidineketene dithioacetals. Furthermore, utilizing this spiro-oxindoles scaffold, biologically important benzimidazole and pyrimidine based poly heterocycles were also synthesized.

Various spiro-oxindole derivatives are obtained by 1,3-dipolar cycloaddition of in situ generated azomethine ylide from isatin and L-proline/L-phenylalanine with α-aroylidineketene dithioacetals.