The reaction of cyclopropanecarbonyl chloride (I) with bis(trimethylsilyl)acetylene (II) gives 1-cyclopropyl-3-(trimethylsilyl)-2-propyn-1-one (III), which is reduced with NaBH4 and CeCl3 in methanol to the corresponding propynol (IV). The condensation of (IV) with 3-hydroxy-4,5-dimethoxybenzaldehyde (V) by means of triphenylphosphine and dimethyl azodicarboxylate in toluene yields the expected propynyl ether (VI), which is cyclized in N,N-diethylaniline at 200 C affording 2-cyclopropyl-7,8-dimethoxy-2H-1-benzopyran-5-carbaldehyde (VII). The condensation of (VII) with 3-anilinopropionitrile (VIII) by means of potassium tert-butoxide in DMSO gives the acrylonitrile (IX), which is finally cyclized with guanidine (X) by means of potassium tert-butoxide in ethanol. (1)
The reaction of cyclopropanecarbonyl chloride (I) with bis(trimethylsilyl)acetylene (II) gives 1-cyclopropyl-3-(trimethylsilyl)-2-propyn-1-one (III), which is reduced with NaBH4 and CeCl3 in methanol to the corresponding propynol (IV). The condensation of propynol (IV) with 3-hydroxy-4,5-dimethoxybenzoic acid methyl ester (XI) by means of triphenylphosphine and dimethyl azodicarboxylate in toluene yields the expected propynyl ether (XII), which is cyclized in N,N-diethylaniline at 200 C affording 2-cyclopropyl-7,8-dimethoxy-2H-1-benzopyran-5-carboxylic acid methyl ester (XIII). Finally, this compound is reduced with NaAlH2(OCH2CH2)2 and morpholine in toluene to give the previously described 2-cyclopropyl-7,8-dimethoxy-2H-1-benzopyran-5-carbaldehyde (VII). The condensation of (VII) with 3-anilinopropionitrile (VIII) by means of potassium tert-butoxide in DMSO gives the acrylonitrile (IX), which is finally cyclized with guanidine (X) by means of potassium tert-butoxide in ethanol.