Nitrogen- and Phosphorus-Containing Lewis Base Catalyzed [4+2] and [3+2] Annulation Reactions of Isatins with But-3-yn-2-one

Nitrogen- and phosphorus-containing Lewis base catalyzed [4+2] and [3+2] annulations of isatins with but-3-yn-2-one proceeded smoothly to give the corresponding spiro[indoline-3,2'-pyran]-2,4'(3'H)-diones and spiro[furan-2,3'-indoline]- 2',4(5H)-diones in good-to-excellent yields under mild conditions. The substrate scope has been carefully examined. Moreover, the additive effect of water has also been investigated in detail along with plausible reaction mechanisms based on previous literature and our own investigations.