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Preparation of (Meth)acrylated Alkyl Phosphates

IP.com Disclosure Number: IPCOM000031855D
Publication Date: 2004-Oct-14
Document File: 4 page(s) / 64K

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Abstract

Reported herein is the utility of solid phase acidic resins as reaction catalysts and their application in simple high yielding processes of making (meth)acrylated alkyl phosphates that are otherwise made via laborious multi-step and wasteful procedures. The processes utilize Amberlyst-15, and the like, as the solid phase catalysts and require only a simple filtration of the recyclable catalyst at the end of the reaction in order to recover the desired product. Neither extra steps nor solvents are required. The acidic monomers produced by this method can be key ingredients in self-etching dental adhesive formulations.

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Preparation of (Meth)acrylated Alkyl Phosphates

Abstract

Reported herein is the utility of solid phase acidic resins as reaction catalysts and their application in simple high yielding processes of making (meth)acrylated alkyl phosphates that are otherwise made via laborious multi-step and wasteful procedures. The processes utilize Amberlyst-15, and the like, as the solid phase catalysts and require only a simple filtration of the recyclable catalyst at the end of the reaction in order to recover the desired product. Neither extra steps nor solvents are required. The acidic monomers produced by this method can be key ingredients in self-etching dental adhesive formulations.

Discussion and Results

ω-Methacryloyloxyalkyl phosphates (Scheme 1) serve as acidic etchants in self-etching dental adhesive formulations and, being polymerizable, have the capability to copolymerize with the other monomers in the formulation such that no hazards to the patient results after curing of the adhesive.

Traditionally, this class of materials is prepared in two steps, the first of which is an esterification of a diol with methacrylic acid in the presence of a soluble acidic catalyst (see Scheme 2). The second step involves phosphorylating the methacrylated alcohol prepared in the first step to give the corresponding phosphate. A successful phosphorylation reaction, which results in a minimum of phosphoric acid by-product, requires a very dry alcohol from the first step. Several laborious work-up steps are required in the first step in order to ensure a complete removal of the soluble catalyst and that the intermediate alcohol is dry enough for the second step.

U.S. Patent No. 4,539,382 (Omura et al.) discloses methods of making various methacrylated alkyl and aromatic alcohols by reacting methacrylic acid with diols in the presence of p-toluenesufonic acid (soluble acid catalyst) at 90ºC along with continuous removal of the water by-product by applying a vacuum. After the reaction is complete, the crude product is either taken neat or dissolved into some organic solvent and then washed with an aqueous sodium bicarbonate solution several times until alkaline, followed by several water washings (5 times on average). The resulting moist, catalyst-free product was then dried by anhydrous Na2SO4 followed by vacuum at 90ºC for several hours (Scheme 3).

One complication of having residual water in the intermediate is the formation of undesired phosphoric acid in the final methacrylated phosphate product (Scheme 4).

Although Omura et al indicated that water can be removed by the multi-step work-up shown in Scheme 3, we have found that it is extremely difficult to remove all the water under the described conditions. Also, applying a vacuum to the product at high temperature can result in undesirable polymerization.

Also, when the methacrylated alcohol was made according to the Omura et al. methods, the amount of the phosphoric acid by-product in the phosphorylated pro...