Related Experiment Video
Updated: Sep 11, 2025

Harnessing the Bioorthogonal Inverse Electron Demand Diels-Alder Cycloaddition for Pretargeted PET Imaging
Published on: February 3, 2015
Combined Inductive and Dispersion Effects Enhance Bioorthogonal Reactivity of Tetrazines Toward Isonitriles
Suprakash Biswas1, Andreas Löffler2, Pushkar Bansal3
1Department of Medicinal Chemistry, University of Utah, 30 S 2000 E, Salt Lake City, UT, 84112, USA.
Abstract:
Inverse-electron demand cycloaddition reactions of tetrazines are widely used in bioorthogonal chemistry, but the opposing effects of substituents on reactivity and stability make optimizing tetrazines for chemical biology applications challenging. Building on the discovery that bulky substituents can unexpectedly enhance both the stability of tetrazines and their reactivity toward isonitriles, we hypothesized that substituents that are both bulky and electron-withdrawing could yield tetrazines with desirable properties. We synthesized a series of tetrazines designed to explore these kinetic properties. A novel computational method quantifying intermolecular atomic contributions to dispersion forces supported the analysis substituent effects on tetrazine reactivity. Study results indicate that tetrazine reactivity is governed by an interplay of frontier-orbital levels, dispersion forces, and conformational preferences. These insights were apparent in the form of a "bromo effect," where bromine atoms enhanced tetrazine reactivity by influencing frontier-orbital levels and increasing dispersion forces. Notably, 3,6-bis(2-bromopropan-2-yl)-1,2,4,5-tetrazine exhibited a ∼80-fold increase in reactivity to isonitriles compared to dimethyltetrazine with high orthogonality to other dienophiles. The 2-bromoprop-2-yl group could also be incorporated into asymmetric tetrazines for tuning reactivity properties. In addition to introducing novel tetrazines for bioorthogonal chemistry, this work provides valuable insights into the role of dispersion forces in the transition states of cycloaddition reactions.
More Related Videos
10:54Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry
Published on: February 4, 2017
07:30A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones
Published on: January 21, 2020
Related Concept Videos
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Diazonium Group Substitution: –OH and –H
Aryldiazonium Salts to Azo Dyes: Diazo Coupling
Directing and Steric Effects in Disubstituted Benzene Derivatives
Radical Reactivity: Intramolecular vs Intermolecular
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene