Research On Nickel/palladium-catalyzed C–P /C–C Bonds Formation Reactions

Transition-metal-catalyzed cross-coupling reactions for carbon–phosphorus bond formation have become the most straightforward and powerful ways for the preparation of organophosphorus compounds in the past two decades, which have widespread applications in biological, pharmaceutical, material, and catalytic sciences. Although some significant achievements in the palladium-catalyzed formation of C–P bonds have been made, the drawbacks of the catalyst systems, such as sensitivity to air, high cost, and toxicity, limit their applications. Nickel has been identified as a useful reagent and catalyst for cross-coupling reactions involving C–C bonds and C–X bonds, however, examples of nickel-catalyzed C–P bond formation are rare. And, most of the existing methods are still plagued with problems including limited substrate scope, relatively drastic conditions, the occasional need to use strong bases or reductants, and the need for airsensitive catalysts.Based on developing highly active, simple, stable and cheap Ni or Pd catalyst systems,we mainly studied the coupling reactions of aryl halides or Py Bro P activated phenols with various phosphorus nucleophiles by using Ni Cl2(dppp) as a catalyst, as well as Suzuki–Miyaura cross-coupling reaction catalysted by arylphosphinamidebase palladacycles. The main results are listed as follows.1. By utilizing a ligand-based strategy, we have achieved a Ni(0)-catalyzed cross-coupling of aryl halides with various phosphorus substrates under relatively mild reaction conditions in the absence of external reductants and supporting ligands. This catalyst system displays a broad applicability that is capable of catalyzing the cross-coupling of aryl bromides, particularly a range of unreactive aryl chlorides, with various types of phosphorus substrates, such as a dialkyl phosphite, diphenylphosphine oxide, and diphenylphosphane.2. By using Py Bro P as actived reagent of phenols, we have developed a new protocol for the construction of C–P bonds via the Ni Cl2(dppp)-catalyzed cross-coupling of phenol substrates. The method displays a broad feasibility that is amenable not only to various phenol derivatives but also to different types of phosphorus nucleophiles. The reaction can be performed via a one-pot operation without the need to isolate the activated phenol intermediates, thereby improving significantly the reaction efficiency.3. We synthesized a novel arylphosphinamide-derived palladacyclic complex which could be used as an efficient and versatile precatalyst for Suzuki-Miyaura cross-coupling under mild conditions. With the presence of 0.5 mol% of precatalyst, a wide variety of aryl bromides and aryltriflates could be coupled very efficiently at ambient temperature and under air atmosphere. This method is suitable for a rich range of boronic acids such as electron-rich and deficient, polyfluoro, and 2-heterocyclic aryl derivatives. In addition to the highly catalytic activity, the palladacyclic complexes exhibit excellent stability toward air and moisture, and can be very easily prepared.4. We developed a Pd-catalyzed protocol for the direct α-arylation of acetic acid. To gain some mechanistic information for this new transformation, a series of control experiments were performed. We speculate that the α-arylation of acetic acid should proceed more plausibly through a Heck-type cross-coupling.