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Anionic Phospho-Fries Rearrangement at Ferrocene: One-Pot Approach to P,O-Substituted Ferrocenes

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posted on 28.04.2014, 00:00 by Marcus Korb, Dieter Schaarschmidt, Heinrich Lang
For the first time the anionic phospho-Fries rearrangement has been successfully applied in ferrocene chemistry, giving access to 1,2-P,O-substituted ferrocenes. The 1,3 (O → C)-migration occurs at ferrocenyl phosphates, thiophosphates, phosphite–borane adducts, and phosphinates by treatment with a base such as lithium diisopropylamide at low temperature, whereas the highest yields were obtained starting from diethylferrocenyl phosphate. Complete reduction of the phosphonate to a primary phosphine and subsequent Stelzer P,C cross coupling allowed the synthesis of Fe­(η5-C5H3-2-OMe-PPh2)­(η5-C5H5) (1). The qualification of 1 as a supporting ligand in palladium-catalyzed Suzuki–Miyaura C,C couplings has been proven by the synthesis of sterically congested tri-ortho-substituted biaryls under mild reaction conditions in good to excellent yields.