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¥Process for the Preparation of N-(Trimethylsilyl)-4-(trimethylsilyloxy)-1,3,5-triazin-2-amine

IP.com Disclosure Number: IPCOM000200985D
Publication Date: 2010-Nov-02
Document File: 2 page(s) / 31K

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The IP.com Prior Art Database

Abstract

€The preparation of the bis(trimethylsilyl) derivative of 5-azacytosine is widely described in the chemical literature. The literature procedures use hexamethyldisilazane (HMDS) as the silylating agent and the reaction solvent with ammonium sulfate as catalyst, and report reaction times varying from 3 hours to 18 hours. An acid catalyst stronger than ammonium sulfate and with better solubility in the reaction solvent may assist in the attainment of the required transition state and accelerate the reaction. However, the choice of the acid must be a careful one; if the acid is too strong, there is the risk of degradation of the silylated product. The ideal catalyst for this reaction would be one that has slightly higher acid characteristics and better solubility in organic solution. Ammonium trifluoromethanesulfonate was selected as a potentially suitable catalyst for the reaction. The acidity of ammonium trifluoromethanesulfonate is higher than that of ammonium sulfate and the trifluoromethanesulfonate group may be advantageous and help this strong acid-weak base salt to dissolve easily in the organic solvent.

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The preparation of the bis(trimethylsilyl) derivative of 5-azacytosine is widely described in the chemical literature 1-5, The literature procedures use hexamethyldisilazane (HMDS) as the silylating agent and the reaction solvent with ammonium sulfate as catalyst, and report reaction times varying from 3 hours to 18 hours. Ionescu and P Blumbergs5 reported a total reaction time of 8 hours to form a clear, pale-yellow solution with addition of a fresh amount of ammonium sulfate after the first 2 hours.  A further drawback of this procedure is the use of hexamethyldisilazane as the reactant and solvent, one consequence of which is that the subsequent removal becomes problematic and residual amounts reside in the product.

The catalyst, ammonium sulfate, in the reported procedure is a weak acid and serves as a proton donor to polarize the silicon-nitrogen bond in hexamethyldisilazane and thereby facilitates the silylation reaction. However, the solubility of ammonium sulfate in hexamethyldisilazane is poor and as a consequence the availability of ammonium sulfate in the system must be limited, leading to a slow inefficient reaction.  An acid catalyst stronger than ammonium sulfate and with better solubility in the reaction solvent may assist in the attainment of the required transition state and accelerate the reaction.  However, the choice of the acid must be a careful one; if the acid is too strong, there is the risk of degradation of the silylated product.  The ideal catalyst for this reaction would be one that has slightly higher acid characteristics and better solubility in organic solution. Based on these criteria, ammonium trifluoromethanesulfonate was selected as a potentially suitable catalyst for the reaction. The acidity of ammonium trifluoromethanesulfonate is higher than that of ammonium sulfate and the trifluoromethanesulfonate group may be advantageous and help this strong acid-weak base salt to dissolve easily in the or...