Intramolecular Halogen Bonds Assist in Activating Carbonyl Groups for the Catalytic Synthesis of Bis(indolyl)methanes
Jian-Wei Han1, Yingying Hou1, Lin Zhu1
1Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, P. R. China.
Abstract:
Ortho-carboxyl substitution increases the acidity of hypervalent diaryliodonium salts and makes them useful catalysts in the synthesis of bis(indolyl)methanes under mild conditions, with yields up to 98%. The halogen bond-assisted hydrogen bonding was demonstrated by crystal structure analysis. The interaction distance of 2.619 Å between I(III) and the carboxyl O atom indicates either a long covalent or a very short halogen bond; analysis of the electron density shows the latter description is appropriate.
More Related Videos
12:27Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes
Published on: September 8, 2013
19:58Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Published on: July 30, 2017
Related Concept Videos
Multiple Halogenation of Methyl Ketones: Haloform Reaction
Halogenation of Alkenes
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Formation of Halohydrin from Alkenes
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
Base-Promoted α-Halogenation of Aldehydes and Ketones
