- One-pot racemization process of 1-Phenyl-1,2,3,4-tetrahydroisoquinoline: A key intermediate for the antimuscarinic agent solifenacin
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(S)-(+)-1-Phenyl-1,2,3,4-tetrahydroisoquinoline, which is the key intermediate in preparing the urinary antispasmodic drug solifenacin, was racemized in quantitative yield by a simple one-pot procedure through N-chlorination with trichloroisocyanuric acid, conversion of the N-chloroamine into the imine hydrochloride, and reduction of the imine double bond. The racemized amine was successfully resolved by d-(-)-tartaric acid obtaining (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline in 81% yield and with 96.7% ee and, from the crystallization mother liquors, the R enriched form. This was racemized by the same one-pot process and resolved by d-(-)-tartaric acid with the same efficiency. Such an approach to the racemization of 1-phenyl-1,2,3,4- tetrahydroisoquinoline can be industrially useful to recycle the waste R enantiomer resulting from the classical resolution used to obtain the S enantiomer on a large scale.
- Bolchi, Cristiano,Pallavicini, Marco,Fumagalli, Laura,Straniero, Valentina,Valoti, Ermanno
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p. 432 - 437
(2013/05/09)
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- The development of an asymmetric hydrogenation process for the preparation of solifenacin
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The successful development of a catalytic imine asymmetric hydrogenation process for the reduction of the hydrochloride salt of 1-phenyl-3,4- dihydroisoquinoline to 1-(S)-phenyl-1,2,3,4-tetrahydroisoquinoline is described. This represents a novel approach to the key intermediate in preparing the urinary antispasmodic drug solifenacin, (1S)-(3R)-1-azabicyclo[2.2.2]oct-3-yl-3, 4-dihydro-1-phenyl-2(1H)-isoquinoline carboxylate. Suitable reaction conditions were identified through an extensive screen of catalysts and combination of solvents and additives. The best reaction conditions: [Ir(COD)Cl] 2-(S)-P-Phos, molar substrate to catalyst ratio (S/C) of >1000/1, THF, 1-2 equiv of H3PO4, 60 °C, 20 bar H2, were reproduced on a 200 g scale (95% isolated yield, 98% ee and >99% HPLC product purity).
- Ruzic, Milos,Pecavar, Anica,Prudic, Darja,Kralj, David,Scriban, Corina,Zanotti-Gerosa, Antonio
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experimental part
p. 1293 - 1300
(2012/09/21)
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