Metal-Free Oxidative Decarbonylative [3+2] Annulation of Terminal Alkynes with Tertiary Alkyl Aldehydes toward Cyclopentenes.

A new metal-free oxidative decarbonylative [3+2] annulation of terminal alkynes with tertiary alkyl aldehydes is presented, which features broad substrate scope and excellent selectivity. The selectivity of this reaction toward cyclopentenes and indenes relies on the nature of the aldehyde substrates. While treatment of tertiary γ,δ-unsaturated aldehydes with common terminal alkynes assembles cyclopentenes, 2-methyl-2-arylpropanals succeed in accessing indenes.

Copper-Catalyzed C-H Oxidative Radical Functionalization and Annulation of Aniline-Linked 1,7-Enynes: Evidence for a 1,5-Hydride Shift Mechanism.

A new copper-catalyzed tandem C-H oxidative radical functionalization and annulation of aniline-linked 1,7-enynes with alkyl nitriles or acetone is described. This reaction allows the selective construction of 1H-cyclopenta[c]quinolines and benzo[j]phenanthridin-6(5H)-ones which rely on the substitution effect at the 2-position of the acrylamide moiety. The mechanism involving a 1,5-hydride shift process is proposed according to the control deuterium-labeled experiment.