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 6 pi-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. (C) 2012 Elsevier Ltd. All rights reserved.