PROCESS FOR PRODUCING OPTICALLY ACTIVE PIPERAZINE COMPOUND
Provided is a method of producing optically active 1-methyl-3-phenylpiperazine of the formula (11) or salt thereof, comprising the following steps 1 to 4, or steps 5 to 7 and step 4, and a method of producing optically active mirtazapine via this method.
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Page/Page column 24
(2008/12/06)
METHOD FOR THE PREPARATION OF AN ENANTIOMER OF A TETRACYCLIC BENZAZEPINE
The present invention relates to a method for the preparation of mirtazapine and tetracyclic analogous compounds having substantial enantiomeric excess of the R or S form. The invention further relates to a novel intermediate and its use for the preparation of mirtazapine having a substantial enantiomeric excess of the R or S form. The method comprising the steps of a: providing a carboxylic acid compound according to Formula I having a substantial enantiomeric excess of the R or S form, b: converting the carboxylic acid group of compound I into a ketone group, producing a ketone compound of Formula II, c: optionally reducing ketone compound II with a mild reduction agent to form the intermediate hydroxy compound of Formula III and d: forming the mirtazapine of Formula IV by reduction of the ketone compound II or of the hydroxy compound III using a strong reduction agent.
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Page/Page column 4-5
(2008/12/04)
A METHOD FOR THE PREPARATION OF AN ENANTIOMER OF A TETRACYCLIC BENZAZEPINE
The present invention relates to a method for the preparation of mirtazapine and tetracyclic analogous compounds having substantial enantiomeric excess of the R or S form. The invention further relates to a novel intermediate and its use for the preparation of mirtazapine having a substantial enantiomeric excess of the R or S form. The method comprising the steps of a: providing a carboxylic acid compound according to Formula (I) having a substantial enantiomeric excess of the R or S form, b: converting the carboxylic acid group of compound I into a ketone group, producing a ketone compound of Formula (II), c: optionally reducing ketone compound II with a mild reduction agent to form the intermediate hydroxy compound of Formula (III) and d: forming the mirtazapine of Formula (IV) by reduction of the ketone compound II or of the hydroxy compound III using a strong reduction agent.
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Page/Page column 10; 11-12
(2008/12/08)
Asymmetric synthesis of (S)-mirtazapine: Unexpected racemization through an aromatic ipso-attack mechanism
An asymmetric synthesis of (S)-mirtazapine has been achieved from the synthesis of the racemate by using (S)-1-methyl-3-phenylpiperazine as the starting material. Unfortunately, significant racemization was encountered in the final step, which involved an electrophilic aromatic ring closure of a alcohol by concentrated sulfuric acid. A significantly higher ee was observed when polyphosphoric acid (PPA) was used instead. A remarkable correlation between the amount of PPA used and the ee of the product was revealed, namely, an increase in the ee upon decreasing the amount of PPA. This trend was paralleled by the formation of an increasing amount of a side-product upon lowering the amount of PPA. The racemization and formation of a side-product can be explained by an ipso-attack mechanism during the electrophilic aromatic ring-closure reaction. This mechanism was supported by a mechanistic study using a deuterium-labeled substrate. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Van Der Linden, Marco,Borsboom, Judith,Kaspersen, Frans,Kemperman, Gerjan
experimental part
p. 2989 - 2997
(2009/04/07)
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