Synthesis of functionalized benzothiophenes and dibenzothiophenes by twofold Heck and subsequent 6π-electrocyclization reactions of 2,3-dibromothiophenes and 2,3-dibromobenzothiophenes

Benzothiophenes and dibenzothiophenes were prepared by twofold Heck reactions of 2,3-dibromothiophene and 2,3-dibromobenzothiophene, respectively, and subsequent thermal 6π-electrocyclization. The Heck reaction of 2,3-dibromothiophene and 2,3-dibromobenzothiophene with 1 equiv of alkenes proceeded with different regioselectivities and afforded 2-alkenylthiophenes and 3-alkenylbenzothiophenes.

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