Copper-mediated 1,4-Conjugate Addition of Boronic Acids and Indoles to Vinylidenebisphosphonate leading to<i>gem</i>-Bisphosphonates as Potential Antiresorption Bone Drugs
wide range of gem‐bisphosphonate tetraethyl esters as precursors for bisphosphonic acids, which are potent inhibitors of bone resorption, bearing alkyl, aryl, and indole substituents in the β position were prepared through the CuII‐catalyzed 1,4‐conjugate addition of boronicacids and indoles to vinylidenebisphosphonate tetraethyl ester.
A new synthetic method characterized by low environmental impact for the synthesis of a wide range of gem-bisphosphonates bearing aryl substituents in β position as potential anti-resorption species to contrast osteoporosis is reported. The pivotal role played by water ensures higher yields compared to the organic medium in the rhodium-catalyzed 1,4-conjugate addition of arylboronic acids to vinylidenebisphosphonate tetraethylester, as well as easy product isolation.