Synthesis and X-ray Structure Determination of Highly Active Pd(II), Pd(I), and Pd(0) Complexes of Di(tert-butyl)neopentylphosphine (DTBNpP) in the Arylation of Amines and Ketones

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• 作者：Lensey L. Hill ; Jason L. Crowell ; Strudwick L. Tutwiler ; Nicholas L. Massie ; C. Corey Hines ; Scott T. Griffin ; Robin D. Rogers ; Kevin H. Shaughnessy ; Gabriela A. Grasa ; Carin C. C. Johansson Seechurn
• 刊名：Journal of Organic Chemistry
• 出版年：2010
• 出版时间：October 1, 2010
• 年：2010
• 卷：75
• 期：19
• 页码：6477-6488
• 全文大小：1124K
• 年卷期：v.75,no.19(October 1, 2010)
• ISSN：1520-6904

文摘

The air-stable complex Pd(η³-allyl)(DTBNpP)Cl (DTBNpP = di(tert-butyl)neopentylphosphine) serves as a highly efficient precatalyst for the arylation of amines and enolates using aryl bromides and chlorides under mild conditions with yields ranging from 74% to 98%. Amination reactions of aryl bromides were carried out using 1−2 mol % Pd(η³-allyl)(DTBNpP)Cl at 23−50 °C without the need to exclude oxygen or moisture. The C−N coupling of the aryl chlorides occurred at relatively lower temperature (80−100 °C) and catalyst loading (1 mol %) using the Pd(η³-allyl)(DTBNpP)Cl precatalyst than the catalyst generated in situ from DTBNpP and Pd₂(dba)₃ (100−140 °C, 2−5 mol % Pd). Other Pd(DTBNpP)₂-based complexes, (Pd(DTBNpP)₂ and Pd(DTBNpP)₂Cl₂) were ineffective precatalysts under identical conditions for the amination reactions. Both Pd(DTBNpP)₂ and Pd(DTBNpP)₂Cl₂ precatalysts gave nearly quantitative conversions to the product in the α-arylation of propiophenone with p-chlorotoluene and p-bromoanisole at a substrate/catalyst loading of 100/1. At lower substrate/catalyst loading (1000/1), the conversions were lower but comparable to that of Pd(t-Bu₃P)₂. In many cases, the tri-tert-butylphosphine (TTBP) based Pd(I) dimer, [Pd(μ-Br)(TTBP)]₂, stood out to be the most reactive catalyst under identical conditions for the enolate arylation. Interestingly, the air-stable Pd(I) dimer, Pd₂(DTBNpP)₂(μ-Cl)(μ-allyl), was less active in comparison to [Pd(μ-Br)(TTBP)]₂ and Pd(η³-allyl)(DTBNpP)Cl. The X-ray crystal structures of Pd(η³-allyl)(DTBNpP)Cl, Pd(DTBNpP)₂Cl₂, Pd(DTBNpP)₂, and Pd₂(DTBNpP)₂(μ-Cl)(μ-allyl) are reported in this paper along with initial studies on the catalyst activation of the Pd(η³-allyl)(DTBNpP)Cl precatalyst.