title: Synthesis of bis(3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoyl)(phenyl)phosphine oxide - a tailor-made photoinitiator for dental adhesives.
abstract: Because of the poor solubility of the commercially available bisacylphosphine oxides in dental acidic aqueous primer formulations, bis(3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoyl)(phenyl)phosphine oxide (WBAPO) was synthesized starting from 3-(chloromethyl)-2,4,6-trimethylbenzoic acid by the dichlorophosphine route. The substituent was introduced by etherification with 2-(allyloxy)ethanol. In the second step, 3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoic acid was chlorinated. The formed acid chloride showed an unexpected low thermal stability. Its thermal rearrangement at 180 ° C resulted in a fast formation of 3-(chloromethyl)-2,4,6-trimethylbenzoic acid 2-(allyloxy)ethyl ester. In the third step, the acid chloride was reacted with phenylphosphine dilithium with the formation of bis(3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoyl)(phenyl)phosphine, which was oxidized to WBAPO. The structure of WBAPO was confirmed by ¹H NMR, ¹³C NMR, ³¹P NMR, and IR spectroscopy, as well as elemental analysis. WBAPO, a yellow liquid, possesses improved solubility in polar solvents and shows UV-vis absorption, and a high photoreactivity comparable with the commercially available bisacylphosphine oxides. A sufficient storage stability was found in dental acidic aqueous primer formulations.
authors.affiliation: Ivoclar Vivadent AG, Bendererstrasse 2, FL-9494 Schaan, Liechtenstein, A-1060 Vienna, Austria. norbert.moszner@ivoclarvivadent.com
authors.forename: Norbert
authors.initials: N
authors.lastname: Moszner
authors.forename: Iris
authors.initials: I
authors.lastname: Lamparth
authors.forename: Jörg
authors.initials: J
authors.lastname: Angermann
authors.forename: Urs Karl
authors.initials: UK
authors.lastname: Fischer
authors.forename: Frank
authors.initials: F
authors.lastname: Zeuner
authors.forename: Thorsten
authors.initials: T
authors.lastname: Bock
authors.forename: Robert
authors.initials: R
authors.lastname: Liska
authors.forename: Volker
authors.initials: V
authors.lastname: Rheinberger