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

[Image: see text] 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-2H,5H-pyrano[3,2-c]chromen-5-ones, 4,4,4′,4′-tetramethyl-1,3,3′,4,4′,5-hexahydro-5′H-spiro-[benzo[b][1,4]diazepine-2,2′-pyrano[3,2-c]-chromen]-5′-ones, and 2,2,4′,4′-tetramethyl-2,3,3′,4′-tetrahydro-5H,5′H-spiro[benzo[b][1,4]-oxazepine-4,2′-pyrano[3,2-c]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.