Related Experiment Video
Updated: Sep 12, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Diazines-to-Diazoles Skeletal Remodeling
Tian-Yu Peng1, Eugene Yew Kun Tan1, Taku Wakabayashi1,2
1School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore637371, Singapore.
Abstract:
Nitrogen-containing heteroarenes, particularly diazines (six-membered dinitrogen aromatics) and diazoles (five-membered dinitrogen aromatics), constitute the bedrock of modern pharmaceutical and agrochemical architectures. Synthetic capability to edit these heteroaromatic scaffolds through precise core-atom transformations opens the door to previously untapped chemical spaces, thus accelerating discovery campaigns for developing pharmaceutical drugs and agrochemicals. Here we report a photocatalytic platform for the skeletal remodeling of diazines into diazoles, encompassing three distinct permutations: conversion of pyrimidines (1,3-diazines) to imidazoles (1,3-diazoles), and pyridazines (1,2-diazines) to pyrazoles (1,2-diazoles) facilitated by formal ring contractions that proceed via either rehybridizative transposition or deletion of an aromatic carbon unit. Key to this strategy is harnessing photocatalytic single-electron transfer (SET) to access dearomatized diazacyclohexadienyl anions, which undergo precisely orchestrated ring contraction via disrotatory 6π-1,5-electrocyclization.
Related Concept Videos
Diazonium Group Substitution: –OH and –H
Carboxylic Acids to Methylesters: Alkylation using Diazomethane
Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions
Aryldiazonium Salts to Azo Dyes: Diazo Coupling
Bone Remodeling
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
