Benzothiophenes nucleophilic substitution

Benzothiazolone, 3-alkyl-, 53 2,3-Benzothiepine, chloro-, 74 Benzothiophenes, nucleophilic substitution of, 370... 

In the copper catalyzed aromatic nucleophilic substitution of aryl halides bromoindole derivatives were converted to the appropriate cyanoindoles. Both 5-bromoindole and its 7V-tosyl derivative gave excellent yields, when a substoichiometric amount potassium iodide was added to the reaction mixture (6.80.), Pyrazole and benzothiophene showed a similar reactivity. The role of the added iodide is to activate the aromatic system through a bromine-iodine exchange.111... 

In the thiophene (75JHC327) and benzothiophene (78JOC4379) series, nucleophilic substitution of hydride ion (Scheme 31) becomes possible due to the ability of 3d-orbitals of the sulfur atom to stabilize negative charge arising in the anionic cr-complex. 

In the thiophene and benzothiophene series, nucleophilic substitution of hydrogen (Scheme 79) becomes possible due to the ability of 3d-orbitals of the sulfur atom to stabilize negative charge arising in an anionic -complex. Thiophene 1,1-dioxides are very good Michael acceptors. The addition of MeSNa to 3,4-di-// r/-bu ty 1 thiophene 1,1-dioxide <2000CL744> takes place in a 2,5- and 2,3-fashion to give a 56 44 mixture of adducts in 94% yield. 

Another system studied is the photostimulated reaction of o-bromobenzaldehyde or 2-bromoacetophenone (300) with SCH2C02Et as a nucleophile. The substitution product 301 in the basic condition forms the anion 302 which leads to benzothiophenes 303 (equation 184)288. The yields are only moderate due to the fragmentation of the radical-anion intermediate. 

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