Supramolecular Halogen Bonds in Asymmetric Catalysis

Abstract

Halogen bonding has received a significant increase in attention in the past 20 years. An important part of this interest has centered on catalytic applications of halogen bonding. Halogen bond (XB) catalysis is still a developing field in organocatalysis, although XB catalysis has outgrown its proof of concept phase. The start of this year witnessed the publication of the first example of a purely XB-based enantioselective catalytic reaction. While the selectivity can be improved upon, there are already plenty of examples in which halogen bonds, among other interactions, play a crucial role in the outcome of highly enantioselective reactions. This paper will give an overview of the current state of the use of XBs in catalytic stereoselective processes.

Dissection of the Origin of π-Holes and the Noncovalent Bonds in Which They Engage

“…Selective binding of anions is one example. Whereas some of the earlier ditopic receptors made use of H-bonds, more recent work has taken advantage of various sorts of σ-hole bonds to improve on the binding strength and selectivity. − The σ-hole bonds have grown in terms of their impact on synthesis and catalysis, − crystal and polymer design, − ionic liquids, biological activity, − chromatography, and electronic materials …”

The Isocyanide Complexes cis-[MCl2(CNC6H4-4-X)2] (M = Pd, Pt; X = Cl, Br) as Tectons in Crystal Engineering Involving Halogen Bonds

“…Strategies of crystal engineering towards the design of solids with controllable structure and tunable physicochemical properties are amongst the well-recognized tools for material chemistry [1][2][3][4][5]. The emergence of halogen bonding (HaB; for reviews on HaB see references [6][7][8][9][10]) during the construction of supramolecular aggregates opens up a route for the optimisation of their valuable properties, such as catalytic activity [11][12][13][14][15], solubility [16,17], melting point [18], thermal expansion [19][20][21][22], colour [23][24][25][26][27], luminescence [28][29][30][31][32][33][34][35][36][37][38][39][40][41], sensing [42,43], biological [44], and magnetic [45] properties. Various tectons [46], including organic species or metal complex...…”

Asymmetric Pnictogen-Bonding Catalysis: Transfer Hydrogenation by a Chiral Antimony(V) Cation/Anion Pair

“…Noncovalent interactions of this class include halogen bonds, ,− chalcogen bonds, − and tetrel bonds, − which are named after the donor atom’s group. These interactions are frequently encountered in crystal structures − and applied regularly in supramolecular assembly − as well as anion recognition. − By contrast, applications in synthetic chemistry have been less studied; only a few organocatalytic protocols have been reported on the implementation of σ-hole interactions throughout the last two decades, with most methods designed around a halogen bond. − …”