合成路线1

Reduction of 2-aminonicotinic acid (I) with LiAlH4 in THF gives (2-amino-3-pyridinyl)methanol (II), which by bromination with Br2 in AcOH yields (2-amino-5-bromo-3-pyridinyl)methanol hydrobromide (III). Substitution of alcohol (III) with aqueous HBr at reflux provides the corresponding bromide (IV), which by cyclocondensation with dimethyl malonate (V) in the presence of NaH in DMF/THF provides methyl 6-bromo-2-oxo-1,2,3,4-tetrahydro-1,8-naphthyridine-3-carboxylate (VI). Hydrolysis of ester (VI) with NaOH in refluxing MeOH, followed by decarboxylation in refluxing HCl leads to 6-bromo-3,4-dihydro-1,8-naphthyridin-2-one (VII) . Heck coupling of aryl bromide (VII) with t-butyl acrylate (VIII) in the presence of Pd(OAc)2, DIEA and P(o-tol)3 in propionitrile/DMF or acetonitrile/DMF affords the naphthyridinyl-acrylate (IX) , whose t-butyl ester group is then cleaved using TFA in CH2Cl2 to afford, after treatment with HCl in dioxane, (E)-3-(7-oxo-6,8-dihydro-5H-1,8-naphthyridin-3-yl)acrylic acid hydrochloride (Xa) . Similarly, hydrolysis of t-butyl ester (IX) using HBr in AcOH yields 3-(7-oxo-6,8-dihydro-5H-1,8-naphthyridin-3-yl)acrylic acid hydrobromide (Xb) . Finally, acrylic acids (Xa) or (Xb) are condensed with N-methyl-N-(3-methylbenzofuran-2-ylmethyl)-amine (XI) using EDC, HOBt and DIEA in DMF .
Chlorination of 3-methylbenzofuran-2-carboxylic acid (XII) with (COCl)2 and catalytic DMF, followed by condensation with CH3NH2 in CH2Cl2 yields the corresponding benzofuran-2-carboxamide (XIII), which is finally reduced with LiAlH4 in THF .Alternatively, 3-methylbenzofuran-2-carbaldehyde (XIV) is condensed with CH3NH2 in MeOH and subsequently reduced with NaBH4 in EtOH .