Titanium-Mediated Domino Cross-Coupling/Cyclodehydration and Aldol-Addition/Cyclocondensation: Concise and Regioselective Synthesis of Polysubstituted and Fused Furans.

Titanium enolates, in situ-generated from readily available ketones and titanium tetraisopropoxide, undergo domino cross-coupling/cyclodehydration or domino Aldol-addition/cyclocondensation with α-chloroketones to provide synthetically valuable furan derivatives. The domino process tolerates a variety of cyclic and acyclic ketones and chloroketones, producing polysubstituted furans and bi-, tri-, and tetracyclic fused furans.

Brønsted-Acid-Catalyzed Friedel-Crafts Reaction and Electrocyclization Cascade of Indoles with α-Functionalized Carbonyls.

Reported here is an efficient Friedel-Crafts-type reaction followed by electrocyclization cascade under an air atmosphere, employing readily available building blocks as starting materials, ethanol as a solvent, and Brønsted acid as a catalyst. On the basis of the cascade strategy, 2-(2-aminophenyl)-9H-carbazole has been furnished with excellent regioselectivity, exceptional functional group tolerance, and tolerated large-scale synthesis. Furthermore, one-pot syntheses of quino[3,4-a]carbazoles have been accomplished, demonstrating the broad synthetic utility of this strategy in the synthesis of valuable heteroaryl-annulated [a]carbazoles.