Related Experiment Video
Updated: Jun 10, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Pyrrolizine-1,3-dione
Hamish McNab1, James Montgomery, Simon Parsons
1School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, UKEH9 3JJ. H.McNab@ed.ac.uk
Abstract:
Pyrrolizine-1,3-dione 4 was made by oxidation of the alcohol 2 using pyridinium chlorochromate. The dione 4 shows ketone properties (e.g. formation of DNP derivative 11) and, in common with other pyrrolizinones, the lactam unit is readily ring-opened by methanol under basic conditions. The active methylene unit of 4 couples readily with diazonium salts to provide the hydrazone 15 whose structure was confirmed by X-ray crystallography. The 'Meldrumsated' derivative 18 exists exclusively as the tautomer 18F; flash vacuum pyrolysis (FVP) of 18 at 700 degrees C gives the pyronopyrrolizine 20 exclusively. Reaction of 4 with DMF acetal gives the dimethylaminomethylene derivative 22 which exists as a mixture of rotamers at room temperature.
Related Concept Videos
Aryldiazonium Salts to Azo Dyes: Diazo Coupling
Basicity of Heterocyclic Aromatic Amines
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
Diazonium Group Substitution: –OH and –H
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism
Preparation of 1° Amines: Azide Synthesis
Azide ions act as good nucleophiles and react with unhindered alkyl halides to form alkyl azides. Alkyl azides do not participate in further nucleophilic substitution reactions, thereby eliminating the chances of polyalkylated products. Alkyl azides are reduced by hydride-based reducing agents, like lithium aluminum...

