Hypervalent Chalcogenonium⋠⋠⋠π Bonding Catalysis.

A proof-of-concept study of hypervalent chalcogenonium⋅⋅⋅π bonding catalysis was performed. A new catalytic strategy using 1,2-oxaselenolium salts as chalcogen bond donors and alkenes as chalcogen bond acceptors is described. The feasibility of this concept is demonstrated by the use of trisubstituted selenonium salts in the metal-free catalytic hydrofunctionalization and polymerization of alkenes via unconventional seleniranium ion-like intermediates. The results indicate that counter anions have a significant effect on the catalysis based on hypervalent chalcogenonium⋅⋅⋅π bonding interactions.

Applications of the DIB-BBr3 Protocol in Bromination Reactions.

Non-symmetrical bromoiodanes are useful for bromination reactions, and some protocols were found to be suitable for specific substrates. Herein, we report the use of a DIB/BBr3 protocol for various bromination reactions, including electrophilic bromination of arenes, carbonyl C-H monobromination, bromolactonization, bromocarbocyclization, intermolecular bromoetherification of olefin, and light-triggered C(sp3)-H bromination.

Access to Bromo-γ-butenolides via Zwitterion-Catalyzed Rearrangement of Cyclopropene Carboxylic Acids.

γ-Butenolides are useful structural motifs in many pharmaceutically relevant compounds. In particular, halogenated γ-butenolides are attractive building blocks because the halogen handles can readily be manipulated to give various functional molecules. In this study, a catalytic synthesis of halogenated γ-butenolides from cyclopropene carboxylic acids was developed using zwitterionic catalysts and N-haloamides as the halogen sources. The catalytic protocol could also be applied to the synthesis of halogenated pyrrolones by using cyclopropene amides as the starting materials.