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.

PhI(OAc)2-mediated 1,2-aminohalogenation of alkynes: a general access to (E)-4-(halomethylene)oxazolidin-2-ones.

A new PhI(OAc)2-mediated 1,2-aminohalogenation of prop-2-yn-1-yl carbamates and various halogen sources is presented with excellent selectivity and high step-economy. The reaction is general and rapid for the construction of diverse (E)-4-(halomethylene)oxazolidin-2-ones through the generation of the three-membered ring or N-radical followed by intramolecular cyclization.

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.

Synthesis of 2-Keto(hetero)aryl Benzox(thio)azoles through Base Promoted Cyclization of 2-Amino(thio)phenols with α,α-Dihaloketones.

An interesting base-promoted protocol for the synthesis of 2-keto(hetero)aryl benzox(thi)azoles has been developed. Starting from commercially available 2-amino(thio)phenols and α,α-dihaloketones, moderate to good yields of the corresponding heterocycles can be achieved. Notably, only EtNH2 was required as the promoter here, and the reaction can be easily performed on a large scale.

Copper/Iron-Catalyzed Aerobic Oxyphosphorylation of Terminal Alkynes Leading to ß-Ketophosphonates.

A copper/iron-catalyzed oxyphosphorylation of alkynes with H-phosphonates through a radical process was developed. The present protocol provides an attractive approach to ß-ketophosphonates in moderate to good yields, with the advantages of readily available substrate, high functional group tolerance and operation simplicity.

Method for transforming alkynes into (E)-dibromoalkenes.

The highly stereoselective bromination of alkynes has been realized by using copper(II) bromide as both the reacting partner and the catalyst, offering a generally efficient synthesis of (E)-dibromoalkenes. The reaction conditions are exceptionally mild, and a wide range of functional groups are well tolerated.