Tandem free-radical addition/substitution chemistry and its application to the preparation of novel AT₁ receptor antagonists

Benzothiophene and benzoselenophene analogues of the thiophene-containing antihypertensives milfasartan and eprosartan were prepared and tested for AT1 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 AT₁ receptor antagonists, with pKв estimates of 7.2-9.5.