Tandem free-radical addition/substitution chemistry and its application to the preparation of novel AT₁receptor antagonists

Benzothiophene and benzoselenophene analogues of the thiophene-containing antihypertensives milfasartan and eprosartan were prepared and tested for AT(1) receptor antagonist properties. While the sulfur-containing systems were prepared following existing methodology, the selenium-containing analogues required the development of novel, tandem free-radical chemistry involving addition of aryl radicals to alkynes, followed by intramolecular homolytic substitution at the higher heteroatom. All four compounds prepared proved to be excellent AT(1) receptor antagonists, with pK(B) estimates of 7.2-9.5.