t -BuOK-Catalyzed Regio- and Stereoselective Intramolecular Hydroamination Reaction Leading to Phthalazinoquinazolinone Derivatives.

We report herein an efficient and practical strategy for the preparation of 5 H -phthalazino[1,2- b ]quinazolin-8(6 H )-one derivatives through a t -BuOK-catalyzed intramolecular hydroamination reaction of functionalized quinazolinones under extremely mild reaction conditions. A variety of quinazolinone substrates are well tolerated to furnish the corresponding products in good to high yields via an exclusive 6- exo-dig cyclization process. The present protocol has the advantages of readily obtainable starting materials, broad substrate scope, and high regio- and stereoselectivity.