AbstractZur Diskussion der Beziehung zwischen der elektronischen Natur der Substituenten und ihrer Stellung werden die Nitrierung, Bromierung und Friedel‐ Crafts‐Acetylierung der Benzo[b lthiophene (I) untersucht.

AbstractDie Brommethylthiophene (I) werden mit den Aminoverbindungen (II) bzw. (IV) zu den 2‐Derivaten (III) bzw. zum 2‐ (Va) bzw. 3‐Derivat (Vb) umgesetzt.

AbstractDie Synthese des Psilocinanalogen (Vb) geht von der Carbonsäure (Ia) aus, die beim Erhitzen mit Kupfer/Chinolin das Benzothiophen (Ib) gibt.

The bromination, nitration, Vilsmeier–Haack formylation, and Friedel–Crafts acetylation reactions of 4-methoxy-benzo[b]thiophen and its 3-methyl derivative have beeen investigated. For 4-methoxybenzo[b]thiophene, these reactions gave the 7-substituted product, whereas for the 3-methyl derivative a mixture of the 2-(ca. 40%) and 7-substituted compounds (ca. 60%) was obtained in each case. For both compounds, dibromination and dinitration gave the 2,7-disubstituted derivative. The structures of the substitution products were determined by n.m.r. spectroscopy.

Electrophilic substitution reactions of 4-hydroxybenzo [b]thiophen and its 3-methyl derivative are described. Formylation under modified Gattermann conditions and bromination with N-bromosuccinimide gave the 5-substituted product in each case, whereas treatment with bromine in carbon tetrachloride gave the corresponding 5,7-dibromo-compound. Nitration in acetic acid gave a mixture of the 5-nitro-, the 7-nitro-, and the 5,7-dinitro-compounds, of which the 5-nitro-compound was the major component in each case. Claisen rearrangement of 4-allyloxybenzo[b]thiophen and its 3-methyl derivative gave the appropriate 5-allyl-4-hydroxy-compound. Fries rearrangement of 4-acetoxybenzo[b]thiophen with aluminium chloride in boiling benzene gave a mixture of 7-acetyl-4-hydroxybenzo[b]thiophen (90%) and its 2,3-dihydro-derivative (7%). Similar treatment of 4-acetoxy-3-methylbenzo[b]thiophen gave a mixture of 7-acetyl-4-hydroxy-3-methylbenzo[b]thiophen (21%) and the 2-acetyl isomer (68%). Bromination of 4-methylsulphonyloxybenzo[b]thiophen in acetic acid gave a mixture of 3-bromo-(60%) and 5-bromo-4-methylsulphonyloxybenzo[b] thiophen (20%) and the corresponding 5,7-dibromo-compound (6%), together with two unidentified products. 3-Bromomethyl-4-methylsulphonyloxybenzo[b]thiophen, obtained by treatment of the corresponding 3-methyl compound with N-bromosuccinimide. was used as a key intermediate in the synthesis of 2-(4-hydroxy-3-benzo[b]thienyl)ethylamine, the sulphur analogue of 4-hydroxytryptamine.

Some 2- and 3-dialkylaminomethyl-5-methoxybenzo[b]thiophens have been prepared from the appropriate bromomethyl compound and secondary amines. The bromomethyl compounds have been converted into the corresponding nitriles and reduced to 2-(5-methoxy-2- or -3-benzo[b]thienyl)ethylamine. 2-(5-Hydroxy-3-benzo[b]thienyl)ethylamine has been prepared from 5-nitro-3-benzo[b]thienylacetic acid and isolated and characterised as its maleate. The isomeric 7-hydroxy-compound has been prepared from 7-hydroxy-3-methylbenzo[b]-thiophen via the nitrile and has been isolated as its hydrochloride.

AbstractDas Benzothiophen (I) ergibt bei der Bromierung bei 0°C das Monobromderivat (II).

AbstractDie Formylierung der Benzothiophene (I) nach Gatterrnann und die Bromierung mit N‐Brom‐succinimid führen als elektrophile Substitutionsreaktionen zu den 5‐substituierten Derivaten (IIa).