合成路线1

The title compound has been synthesized by two closely related methods. Claisen condensation of 3,4-dimethoxyphenylacetonitrile (I) with ethyl formate produced the cyano aldehyde sodium enolate (II), which was further O-acylated with benzenesulfonyl chloride to afford (III). The aminothiophene derivative (V) was prepared by cyclization of (III) with methyl thioglycolate (IV) under basic conditions. A pyrrole ring was then introduced in (V) through a Paal-Knorr synthesis employing 2,5-dimethoxytetrahydrofuran (VI) in the presence of 4-chloropyridinium chloride, yielding (VII). Refluxing of ester (VII) in pyrrolidine (VIII) gave rise to amide (IX). The intramolecular cyclization of (IX) under Vilsmeier conditions furnished the tricyclic system (X). Finally, regioselective cleavage of the meta methoxy group of (X) by means of AlCl3 yielded the target compound.