Syntheses of Combretastatins D-1, D-2, and D-4 via Ring Contraction by Flash Vacuum Pyrolysis
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Updated: Mar 10, 2026

Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core
Published on: October 24, 2017
Marina Harras, Wolfgang Milius, R Alan Aitken1
1EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews, Fife KY16 9ST, United Kingdom.
Abstract:
We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2.
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