An Efficient One-pot Synthesis of Novel Spiro Cyclic 2-Oxindole Derivatives of Pyrimido[4,5-b]Quinoline, Pyrido[2,3-d:6,5-d′]Dipyrimidine and Indeno[2′,1′:5,6]Pyrido [2,3-d]Pyrimidine in Water

A novel and facile one‐pot synthesis of spiro cyclic 2‐oxindole derivatives of pyrimido[4,5‐b]quinoline‐4,6‐dione, pyrido[2,3‐d:6,5‐d′]dipyrimidine‐2,4,6‐trione, and indeno[2′,1′:5,6]pyrido [2,3‐d]pyrimidine employing 6‐aminothiouracil (or 6‐aminouracil), isatin, and cyclic 1,3‐diketone (e.g. 1,3‐indanedione, dimedone, or barbituric acid) has been developed.