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Abstract

6,7-Dihydro-5H-imidazo[1,5-a]pyridin-8-one (I), is obtainable in high yields by: 1) a process which proceeds from a suitably protected C-(3-hydroxypyridin-2-yl)methylamine whose amine is converted to the formamide which is then cyclized to the imidazo[1,5-a]pyridine and hydrogenated to the 6,7-dihydro-5H-imidazo[1,5-a]pyridin-8-one, and suitably protected C-(3-hydroxypyridin-2-yl)methylamines can be prepared either in 2 steps proceeding from commercially available 3-hydroxy-2-cyanopyridine [932-35-4] or in 3 steps proceeding from commercially available 2-hydroxymethylpyridin-3-ol [14173-30-9]; 2) a process for preparing 4-hydroxy-1-(1H-imidazol-4-yl)butan-1-one, an intermediate from the synthesis of 6,7-dihydro-5H-imidazo[1,5-a]pyridin-8-one (formula I), as described in WO 2002/040484, proceeding from N,N-dimethyl-2-(trialkylsilanyl)imidazole-1-sulphonamide by lithiation and subsequent reaction with a suitably protected 4-hydroxybutyraldehyde, followed by oxidation of the secondary alcohol, acid-induced deprotection of the imidazole and deprotection of the alcohol functionality; 3) a process which proceeds from 5,6,7,8-tetrahydroimidazo[1,5-a]pyridine [38666-30-7], which is oxidized.

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First Claim