Organocatalyzed Phospha-Michael Addition: A Highly Efficient Synthesis of Customized Bis(acyl)phosphane Oxide Photoinitiators |
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| Authors: | Dr Riccardo Conti Dr Anna Widera Dr Georgina Müller Csilla Fekete Debora Thöny Frederik Eiler Prof Zoltán Benkő Prof Hansjörg Grützmacher |
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| Institution: | 1. Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1–5/10, 8093 Zürich, Switzerland;2. Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, 1111 Budapest, Műegyetem rakpart 3., Hungary |
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| Abstract: | Addition of the P−H bond in bis(mesitoyl)phosphine, HP(COMes)2 (BAPH), to a wide variety of activated carbon–carbon double bonds as acceptors was investigated. While this phospha-Michael addition does not proceed in the absence of an additive or catalyst, excellent results were obtained with stoichiometric basic potassium or caesium salts. Simple amine bases can be employed in catalytic amounts, and tetramethylguanidine (TMG) in particular is an outstanding catalyst that allows the preparation of bis(acyl)phosphines, R−P(COMes)2, under very mild conditions in excellent yields after only a short time. All phosphines RP(COMes)2 can subsequently be oxidized to the corresponding bis(acyl)phosphane oxides, RPO(COMes)2, a substance class belonging to the most potent photoinitiators for radical polymerizations known to date. Thus, a simple and highly atom economic method has been found that allows the preparation of a broad range of photoinitiators adapted to their specific field of application even on a large scale. |
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| Keywords: | acylphosphane oxides organocatalysis phospha-Michael addition photoinitiators radical polymerization |
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