Resonance‐Assisted Hydrogen Bonding as a Driving Force in Synthesis and a Synthon in the Design of Materials

Abstract

Resonance-assisted hydrogen bonding (RAHB), a concept introduced by Gilli and co-workers in 1989, concerns a kind of intramolecular H-bonding strengthened by a conjugated π-system, usually in 6-, 8-, or 10-membered rings. This Review highlights the involvement of RAHB as a driving force in the synthesis of organic, coordination, and organometallic compounds, as a handy tool in the activation of covalent bonds, and in starting moieties for synthetic transformations. The unique roles of RAHB in molecular recognition and switches, E/Z isomeric resolution, racemization and epimerization of amino acids and chiral amino alcohols, solvatochromism, liquid-crystalline compounds, and in synthons for crystal engineering and polymer materials are also discussed. The Review can provide practical guidance for synthetic chemists that are interested in exploring and further developing RAHB-assisted synthesis and design of materials.

Synthesis of 3‐Methylidene‐1‐tosyl‐2,3‐dihydroquinolin‐4(1H)‐ones as Potent Cytotoxic Agents

“…Molecular conformation is constrained by the strong, planar resonance‐assisted hydrogen bond (RAHB) which connects phosphoryl bond and hydroxy group (blue line, Figure ). RAHB's exist in numerous C,H,N,O compounds and additionally in several β ‐ketosulfones . However, to the best of our knowledge, these bonds have not been identified and characterized in organic phosphorus compounds yet.…”

Copper(II) Complexes of Arylhydrazone of 1H-Indene-1,3(2H)-dione as Catalysts for the Oxidation of Cyclohexane in Ionic Liquids

“…The ILs showed a better performance than the conventional solvent for the copper complex 1. No catalytic activity was observed for 2 in the presence of an IL.Despite the potential applications of arylhydrazone and their metal complexes, mainly in the oxidation of alkanes and alcohols [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], the use of such compounds in catalysis is still an understudied area. In pursuit of our interest in the transition metal-catalysed peroxidative [by tert-butyl hydroperoxide (TBHP) or H 2 O 2 ] oxidation of hydrocarbons in ILs [36-39], we have tested a pair of already known [51] copper(II) complexes, viz.…”

Tetrel, Chalcogen, and Charge-Assisted Hydrogen Bonds in 2-((2-Carboxy-1-(substituted)-2-hydroxyethyl)thio) Pyridin-1-ium Chlorides

“…negative charge-assisted, positive charge-assisted, conventional (or "neutral"), and resonance-assisted, have been well employed in crystal growth and design [10].On the other hand, the charge-assisted hydrogen bonding (CAHB), viz. interactions of the X(+)-H···Y(−) type with the X-H donor belonging to a cation and the Y acceptor belonging to an anion, constitutes a particularly powerful tool used in the synthesis and design of new compounds [9,20,21]. CAHBs can control a great variety of synthetic operations involving molecules with groups exhibiting acid-base properties [20,21].…”

“…interactions of the X(+)-H···Y(−) type with the X-H donor belonging to a cation and the Y acceptor belonging to an anion, constitutes a particularly powerful tool used in the synthesis and design of new compounds [9,20,21]. CAHBs can control a great variety of synthetic operations involving molecules with groups exhibiting acid-base properties [20,21]. Due to the strength and directionality of the CAHB, this type of noncovalent interaction has an impact on the synthesis of coordination compounds [9], crystal engineering [20][21][22][23], etc.…”

“…CAHBs can control a great variety of synthetic operations involving molecules with groups exhibiting acid-base properties [20,21]. Due to the strength and directionality of the CAHB, this type of noncovalent interaction has an impact on the synthesis of coordination compounds [9], crystal engineering [20][21][22][23], etc. In most cases, due to the additional electrostatic interactions involved, CAHBs are stronger in comparison to normal hydrogen bonds.On the other hand, α-hydroxy carboxylic acids are versatile and powerful intermediates for the synthesis of various chiral compounds with unique properties [24][25][26][27].…”