The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

Visible-light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. Photocatalytic variants have been reported for many important transformations, such as cross-coupling reactions, α-amino functionalizations, cycloadditions, ATRA reactions, or fluorinations. To help chemists select photocatalytic methods for their synthesis, we compare in this Review classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed under milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, such as air, oxygen, or amines. Does visible-light photocatalysis make a difference in organic synthesis? The prospect of shuttling electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible-light-absorbing photocatalyst holds the promise to improve current procedures in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown, especially by merging photocatalysis with organo- or metal catalysis.

Visible-Light Photocatalysis: Does It Make a Difference in Organic Synthesis?

Palladium-catalyzed alkynylation.

Halogen Bonding in Supramolecular Chemistry.

2.4.2. Interpenetrated Ladders 711 2.4.3. Unusual Motifs of Ladders 713 2.4.4. Properties of Ladderlike Chains 713 2.5. Rotaxane Polymers 714 2.5.1. 1D Polyrotaxanes 714 2.5.2. 2D Polyrotaxanes 715 2.5.3. 3D Polyrotaxanes 716 2.5.4. Hydrogen-Bonded Polyrotaxanes 716 2.6. Ribbon/Tape Polymers 717 2.7. Metal Cluster As Building Blocks for 1D CP 718 2.7.1. Metal Carboxylate Clusters 718 2.7.2. Metal Halide Clusters 719 2.7.3. Metal Chalcogenide Clusters 720 2.7.4. Polyoxometalate Clusters 721 2.7.5. Single Molecular Magnets as Building Blocks 722

One-Dimensional Coordination Polymers: Complexity and Diversity in Structures, Properties, and Applications

The structures and molecular packing of tribromo- and triiodomesitylene are reported and compared to that of trichloromesitylene. Attractive triangular X3 interactions dominate the molecular packing in all three structures. The nonspherical atomic charge distribution on the halogens results in the formation donor−acceptor interactions in which each halogen atom is simultaneously a donor and an acceptor. These triangular X3 (X = Br or I) interactions result in the formation of 2-dimensional sheetlike structures.

Triangular halogen-halogen-halogen interactions as a cohesive force in the structures of trihalomesitylenes

Rate constants for halogen atom transfer from representative α-halocarbonyl compounds to primary alkyl radicals

n-butane isomerization on sulfated zirconia was studied in the temperature range 393–473 K. Rapid deactivation occurs, when the reaction is carried out in He carrier gas. In contrast, stable stationary activity was observed in H2 carrier gas. In situ Raman and UV-VIS diffuse reflectance spectroscopy and ESR showed that the deactivation is caused by the formation of allylic and polyenylic cations and polycyclic aromatic compounds, the formation of which is largely prevented in the presence of H2. Deactivated catalysts can be fully regenerated by treatment at 723–753 K in flowing O2. The regeneration process was also followed by in situ spectroscopies.

n-butane isomerization on sulfated zirconia. Deactivation and regeneration as studied by Raman, UV-VIS diffuse reflectance and ESR spectroscopy

A general method for the synthesis of γ-and δ-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu 3 SnH, onto carbon-carbon multiple bonds is described. This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction.Monocyclic,fused bicyclic, and spirocyclic lactones are formed in good to excellent yield.Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu 3 SnH affords the corresponding 3-butenyl lactones

Synthesis of γ- and δ-lactones by free-radical annelation of Se-phenyl selenocarbonates

Etude de la reactivite relative d'acetates allyliques et propargyliques vis-a-vis de substitutions par des nucleophiles divers catalysees par le palladium

Eric Bosch

Papers

Triangular halogen-halogen-halogen interactions as a cohesive force in the structures of trihalomesitylenes

Rate constants for halogen atom transfer from representative α-halocarbonyl compounds to primary alkyl radicals

n-butane isomerization on sulfated zirconia. Deactivation and regeneration as studied by Raman, UV-VIS diffuse reflectance and ESR spectroscopy

Synthesis of γ- and δ-lactones by free-radical annelation of Se-phenyl selenocarbonates

Palladium-Catalyzed Propargylic vs, Allylic Alkylation