An atom-economic Pd(OAc)2-catalyzed tandem cyclization of alkynones to synthesize pentaleno[2,1-b]indoles was developed efficiently. In the formed tetracyclic indole framework, two neighboring stereocenters, one being all-carbon quaternary, are being constructed in a single process with excellent diastereoselectivity. This reaction was initiated by aminopalladation of alkynes and quenched by addition to the intramolecular carbonyl groups.

AbstractA novel palladium(II)-catalyzed cyclization of aniline-tethered alkynyl cyclohexadienones is reported. This reaction offers an atom-economical and redox-neutral access to various cyclohexenone-fused tetrahydropyrano[3,4-b]indoles with high yield and excellent enantioselectivity. Remarkably, this work represents the first example on a transition-metal-catalyzed asymmetric intramolecular aminopalladation/1,4 addition sequence.

A Pd(OAc)2-catalyzed cyclization reaction of ortho-electron-deficient alkynyl-substituted aryl aldehydes with indoles was accomplished, providing an efficient and economical way to synthesize indole-substituted indanones. The electron-withdrawing group attached to the alkyne and the nucleophilic indole play important roles in the formation of the indanone ring.

A cationic Pd(II)-catalyzed cascade cyclization reaction of alkyne-tethered carbonyl compounds was developed. This reaction is initiated by intramolecular oxypalladation of alkynes with an ester group followed by 1,2-addition of the formed C–Pd(II) bond to the carbonyl group, providing a highly efficient method for the synthesis of cyclohexane-fused isocoumarins.

An efficient cyclization of N-tosyl-aniline tethered allenyl aldehydes and arylboronic acids catalyzed by cationic palladium complex is developed. This annulation reaction provides a convenient process for the synthesis of 3,4-cis-1,2,3,4-tetrahydroquinoline derivatives in high yields with excellent diastereoselectivity and enantioselectivity.

A highly efficient, redox-free Pd(II)-catalyzed tandem cyclization reaction initiated by intramolecular aminopalladation of alkynes followed by nucleophilic addition to nitriles is developed. This method provides a versatile approach for the synthesis of six- to eight-membered ring-fused indoles in one step and has also shown advantages in the formal synthesis of (±)-aspidospermidine.

A palladium(II)-catalyzed efficient synthesis of heterocycle-fused β-naphthylamines was accomplished via nucleophilic addition of a carbon–palladium bond to the intramolecular cyano group initiated by nucleopalladation (oxypalladation or aminopalladation) of alkynes.

A palladium(II)-catalyzed annulation of alkenylindoles with diarylethynes initiated by C–H bond activation was developed. This method provided a convenient way for the synthesis of dihydrocyclopenta[b]indoles by enyne cyclization initiated by C–H bond activation.

A cationic Pd(II)-catalyzed reductive cyclization of alkyne-tethered ketones or aldehydes using ethanol as hydrogen source under mild conditions was developed. The reaction is an environmentally benign synthetic method and proceeds efficiently to give useful N-heterocycles or carbocycles bearing an exocyclic double bond and a hydroxyl group in high yield.

Cationic Pd(II)-catalyzed enantioselective arylative cyclization of alkyne-tethered enals or enones initiated by carbopalladation of alkynes was developed without the necessity of a redox system.