反应详情

In analogy to the procedure described in example 91 b], 7-benzyloxy-benzo[b]thiophene (prepared from benzo[b]thiophen-7-ol [J. Chem. Soc., Perkin Trans. 1 (1983), (12), 2973-7], benzylchloride, potassium carbonate in N,N-dimethylformamide at room temperature) was reacted with dichloromethyl methyl ether in dichloromethane at 0° C. to give 7-benzyloxy-benzo[b]thiophene-4-carbaldehyde. Treatment of 7-benzyloxy-benzo[b]thiophene-4-carbaldehyde with (ethoxy-ethoxycarbonyl-methyl)-triphenyl-phosphonium chloride and potassium carbonate in 2-propanol in analogy to the procedure described in example 93 a] gave 3-(7-benzyloxy-benzo[b]thiophen-4-yl)-2(Z,E)-ethoxy-acrylic acid ethyl ester. Reduction of 3-(7-benzyloxy-benzo[b]thiophen-4-yl)-2(Z,E)-ethoxy-acrylic acid ethyl ester with magnesium in THF/MeOH (1:1) at 50° C. in analogy to the procedure described in example 93 b] yielded [rac]-3-(7-benzyloxy-benzo[b]thiophen-4-yl)-2-ethoxy-propionic acid methyl ester, subsequent removal of the benzyl protective function with dimethyl sulfide and boron trifluoride diethyl etherate in dichlormethane at room temperature in analogy the procedure described in example 93 c] gave [rac]-2-ethoxy-3-(7-hydroxy-benzo[b]thiophen-4-yl)-propionic acid methyl ester as light yellow oil.