The esterification of 2-nitroterephthalic acid (I) with isopropanol by means of dry HCl gives the corresponding dusoproyl ester (II), which by reaction with benzylmercaptane by means of NaH in DMF yields diisopropyl 2-benzylthioterephthalate (III). This compound is hydrolyzed with KOH in refluxing methanol affording the correspon-ding acid (IV), which is converted into its diacid chloride (V) by treatment with refluxing SOCl2. The cyclization of (V) with AlCl3 in methylene chloride - nitromethane affords 6,11-dihydrodibenzo[b]thiepin-11-one-3-carbonyl chloride (VI), which is treated with diazomethane in ether - methylene chloride to yield the 3-diazoacetyl derivative (VII). The Arndt-Eister reaction of (VII) with silver benzoate in refluxing methanol affords methyl 6,11-dihydrodibenzo[b,e]thiepin-11-one-3-acetate (VIII), which is finally hydrolyzed with KOH in refluxing methanol.

The esterification of 2-nitroterephthalic acid (I) with isopropanol by means of dry HCl gives the corresponding dusoproyl ester (II), which by reaction with benzylmercaptane by means of NaH in DMF yields diisopropyl 2-benzylthioterephthalate (III). This compound is hydrolyzed with KOH in refluxing methanol affording the correspon-ding acid (IV), which is converted into its diacid chloride (V) by treatment with refluxing SOCl2. The cyclization of (V) with AlCl3 in methylene chloride - nitromethane affords 6,11-dihydrodibenzo[b]thiepin-11-one-3-carbonyl chloride (VI), which is treated with diazomethane in ether - methylene chloride to yield the 3-diazoacetyl derivative (VII). The Arndt-Eister reaction of (VII) with silver benzoate in refluxing methanol affords methyl 6,11-dihydrodibenzo[b,e]thiepin-11-one-3-acetate (VIII), which is finally hydrolyzed with KOH in refluxing methanol.