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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Cyclo-oligomerization of isocyanates with Na(PH2) or Na(OCP) as "P-" anion sources
Dominikus Heift1, Zoltán Benkő1,2, Hansjörg Grützmacher1,3
1Department of Chemistry and Applied Biosciences , ETH Zurich , CH-8093 Zurich , Switzerland . Email: hgruetzmacher@ethz.ch ;
Abstract:
We show that the 2-phosphaethynolate anion, OCP-, is a simple and efficient catalyst for the cyclotrimerization of isocyanates. This process proceeds step-wise and involves five-membered heterocycles, namely 1,4,2-diazaphospholidine-3,5-dionide anions and spiro-phosphoranides as detectable intermediates, both of which were also found to be involved in the catalytic conversion. These species can be considered as adducts of a phosphide anion with two and four isocyanate molecules, respectively, demonstrating that the OCP- anion acts as a formal "P-" source. The interconversion between these anionic species was found to be reversible, allowing them to serve as reservoirs for unique phosphorus-based living-catalysts for isocyanate trimerization.
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