Bran-New Four-Molecule and Five-Molecule Cascade Reactions for One-Pot Synthesis of Pyrano[3,2-]chromen-5-ones and Spiro[benzo[][1,4]diazepine-2,2'-pyrano[3,2-]chromen]-5'-ones under Catalyst- and Solvent-Free Conditions.

Herein, two versatile bran-new methods have been developed for building three new kinds of complicated-framework compounds including 2,4,4-trimethyl-2-(phenylamino)-3,4-dihydro-2,5-pyrano[3,2-]chromen-5-ones, 4,4,4',4'-tetramethyl-1,3,3',4,4',5-hexahydro-5'-spiro-[benzo[][1,4]diazepine-2,2'-pyrano[3,2-]-chromen]-5'-ones, and 2,2,4',4'-tetramethyl-2,3,3',4'-tetrahydro-5,5'-spiro[benzo[][1,4]-oxazepine-4,2'-pyrano[3,2-]chromen]-5'-ones in a one-pot manner via four-molecule and five-molecule cascade reactions of commercially available 4-hydroxychromen-2-one, substituted anilines, and acetone. In consideration of these impressive features including no need of additional catalysts and solvents, moderate to good yields, excellent site-selectivity, and broad substrate/functional group tolerance, we believe that the two present protocols should have the potential for broad synthetic utility.