Construction of Conjugated 1,3-Enynes via Pd-Catalyzed Cascade Alkynylation of Aryl Phenol-Tethered Alkynes with Alkynyl Bromides.

An efficient Pd-catalyzed cascade alkynylation of aryl phenol-tethered alkynes with alkynyl bromides is described. This protocol could provide various conjugated 1,3-enynes possessing a polysubstituted spirocyclohexadienone, as well as an all-carbon tetrasubstituted alkene moiety. The products could also undergo ring-expansion and cyclization transformations under different conditions to convert to diverse fused cyclic scaffolds.

Palladium-Catalyzed Cascade Allylative Dicarbofunctionalization of Aryl Phenol-Tethered Alkynes with Allyl Iodides: Synthesis of Skipped Dienes.

A palladium-catalyzed cascade allylative dicarbofunctionalization of aryl phenol-tethered alkynes with allyl iodides is described. A series of polysubstituted spirocyclo-containing skipped dienes with an all-carbon tetrasubstituted alkene unit are synthesized through this convenient process. The cascade reaction proceeds selectively through dearomative C-allylation instead of O-allylation of aryl phenols.

Palladium-Catalyzed Cascade Cyclization/Dearomatization/Arylation of Alkyne-Containing Phenol-Based Biaryls with Aryl Halides: An Entry to Diversely Functionalized Spirocyclohexadienones.

A convenient method for the synthesis of aryl-functionalized spirocyclohexadienone scaffolds from alkyne-containing phenol-based biaryls with aryl halides via palladium-catalyzed cyclization/dearomatization/arylation is developed. The approach provides a series of spirocyclohexadienone molecules in moderate to high yields. The reaction occurs chemoselectively through dearomative C-arylation rather than common O-arylation of phenols.

Palladium-Catalyzed Cascade Carbopalladation/Phenol Dearomatization Reaction: Construction of Diversely Functionalized Spirocarbocyclic Scaffolds.

A novel palladium-catalyzed cascade carbopalladation/phenol dearomatization reaction has been achieved. The process provides a variety of indolone-, dihydrobenzofuran-, dihydrobenzopyran- and hydroquinoline-containing spirofused molecules bearing two quaternary centers in moderate to good yields. The potential synthetic utility of this method is demonstrated by a gram-scale experiment and further transformations.

Palladium-Catalyzed Domino Cyclization/Alkylation of Terminal Alkynes: Synthesis of Alkynyl-Functionalized Azaindoline Derivatives.

A novel palladium-catalyzed domino cyclization/alkylation of terminal alkynes was achieved for the synthesis of alkynyl-functionalized 3,3-disubstituted azaindoline derivatives under air atmosphere conditions. Various types of terminal alkynes, including aromatic alkynes, aliphatic alkynes, and ferrocene acetylene, can undergo the process successfully. The protocol provides a range of alkynyl-functionalized azaindoline scaffolds bearing a quarternary carbon center.