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We have elaborated a two-step catalytic approach to nafoxidine, a key precursor to lasofoxifene. Firstly, an efficient α-arylation of 6-methoxy-3,4-dihydronaphthalen-1(2H)-one with chlorobenzene was developed, which operates at low 0.1 mol% Pd-132 catalyst loading in the presence of 1.9 equivalents of sodium tert-butoxide at 60 °C in 1,4-dioxane and provides 6-methoxy-2-phenyl-3,4-dihydronaphthalen-1(2H)-one in 90% yield. Secondly, we have demonstrated that 6-methoxy-2-phenyl-3,4-dihydronaphthalen-1(2H)-one can be converted to nafoxidine in 61% yield via CeCl3 promoted reaction with (4-(2-(pyrrolidin-1-yl)ethoxy)phenyl)lithium, which is formed in-situ from the corresponding arylbromide precursor and n-butyllithium. Altogether, the shortest two-step approach to nafoxidine from simple tetralone commodity starting material has been developed with overall 55% yield. The developed synthetic approach to nafoxidine has several beneficial aspects over the one used in the synthetic route primarily developed for the preparation of lasofoxifene.

The reduction of Pd(II) intermediates to Pd(0) is a key elementary step in a vast number of Pd-catalyzed processes, ranging from cross-coupling, C–H activation, to Wacker chemistry. For one of the most powerful new generation phosphine ligands, PtBu3, oxidation state Pd(I), and not Pd(0), is generated upon reduction from Pd(II). The mechanism of the reduction of Pd(II) to Pd(I) has been investigated by means of experimental and computational studies for the formation of the highly active precatalyst {Pd(μ-Br)(PtBu3)}2. The formation of dinuclear Pd(I), as opposed to the Pd(0) complex, (tBu3P)2Pd was shown to depend on the stoichiometry of Pd to phosphine ligand, the order of addition of the reagents, and, most importantly, the nature of the palladium precursor and the choice of the phosphine ligand utilized. In addition, through experiments on gram scale in palladium, mechanistically important additional Pd- and phosphine-containing species were detected. An ionic Pd(II)Br3 dimer side product was isolated...

The development of palladium-catalyzed α-arylation of carbonyl compounds has emerged as a new avenue in the design of new routes for the synthesis of natural products and active pharmaceutical ingredients (APIs). In many cases, syntheses based on α-arylation strategies provide elegant routes in terms of increasing the overall yields, improving the synthesis scope, and decreasing the number of steps. This microreview aims to highlight the importance of palladium-catalyzed α-arylation methodologies, covering a range of notable reported examples of the total syntheses of structurally important compounds, thereby highlighting the importance of this powerful methodology for key steps in organic synthesis.

The preformed catalyst [Ir(Cl)(COD)(1,10-phenanthroline)] (2; COD = cyclooctadiene) was found to be highly effective in a model reaction for the borylation of N-Boc-indole at the 3-position with B2pin2 (pin = pinacolato) as the borylating agent to give consistently 99% yield with 0.5 mol % catalyst loading. The corresponding in situ formed catalyst from [Ir(Cl)(COD)]2 and 1,10-phenanthroline provided very inconsistent results for the same reaction (0–94% conversion). We propose this to be due to the competing formation of a catalytically inactive cationic complex, [Ir(COD)(1,10-phenanthroline)]+Cl– (1), in a noncoordinating solvent such as octane. Complexes 1 and 2 were characterized using solid-state NMR (13C and 35Cl) in conjunction with XPS to be cationic and neutral, respectively. The X-ray crystal structure of a pentavalent neutral Ir complex, [Ir(Cl)(COD)(2,2′-bipyridine)] (3), was also obtained for comparison purposes. Using catalyst 2, the total synthesis of Meridianin G was accomplished in 87% ov...

An examination of the [{Pd(cinnamyl)Cl}(2)]/Mor-DalPhos (Mor-DalPhos = di(1-adamantyl)-2-morpholinophenylphosphine) catalyst system in Buchwald-Hartwig aminations employing ammonia was conducted to better understand the catalyst formation process and to guide the development of precatalysts for otherwise challenging room-temperature ammonia monoarylations. The combination of [{Pd(cinnamyl)Cl}(2)] and Mor-DalPhos afforded [(κ(2)-P,N-Mor-DalPhos)Pd(η(1)-cinnamyl)Cl] (2), which, in the presence of a base and chlorobenzene, generated [(κ(2)-P,N-Mor-DalPhos)Pd(Ph)Cl] (1 a). Halide abstraction from 1 a afforded [(κ(3)-P,N,O-Mor-DalPhos)Pd(Ph)]OTf (5), bringing to light a potential stabilizing interaction that is offered by Mor-DalPhos. An examination of [(κ(2)-P,N-Mor-DalPhos)Pd(aryl)Cl] (1 b-f) and related precatalysts for the coupling of ammonia and chlorobenzene at room temperature established the suitability of 1 a in such challenging applications. The scope of reactivity for the use of 1 a (5 mol %) encompassed a range of (hetero)aryl (pseudo)halides (X = Cl, Br, I, OTs) with diverse substituents (alkyl, aryl, ether, thioether, ketone, amine, fluoro, trifluoromethyl, and nitrile), including chemoselective arylations.

Strategies for the development of Pd catalysts based on utilization of L2Pd and LPd species, beyond the contributions of the 2010 Nobel Laureates Richard Heck, Ei-ichi Negishi, and Akira Suzuki, along with their contemporaries, are reviewed. These well-defined, preformed Pd catalysts improve the selectivity and activity of selected cross-coupling reactions by reducing the metal loading and the ligand-to-metal ratios. This review describes predominantly the development of Pd precatalysts over the last 10 years and highlights the benefits often observed when using well-defined preformed catalysts relative to those generated in situ.

Im Jahr 2010 wurden Richard Heck, Ei-ichi Negishi und Akira Suzuki in den illustren Kreis der Chemie-Nobelpreistrager aufgenommen. Begrundet wurde diese Auszeichnung mit ihrer Rolle bei der Entdeckung und Entwicklung von praktischen Methoden zur C-C-Bindungsbildung. Ausgelost durch ihre Beitrage uber hochst nutzliche palladiumkatalysierte Kreuzkupplungen, hat sich seit den fruhen 1970er Jahren die Auswahl an verfugbaren Strategien und Methoden in der modernen organischen Synthese grundlegend verandert – sowohl fur Chemiker an Hochschulen wie auch in der Industrie. Dieser Aufsatz vollzieht die historische Entwicklung dieser leistungsstarken Reaktionen nach: von den bahnbrechenden Entdeckungen bis hin zu den Kreuzkupplungsverfahren, die heute in der Synthese angewendet und hoch geschatzt werden.

A series of Pd(R-allyl)LCl complexes [R = H, 1-Me, 1-Ph, 1-gem-Me(2), 2-Me; L = Q-Phos, P(t-Bu)(3), P(t-Bu)(2)(p-NMe(2)C(6)H(4)), P(t-Bu)(2)Np] have been synthesized and evaluated in the Buchwald-Hartwig aminations in detail, in addition to the preliminary studies on Suzuki coupling and α-arylation reactions. Pd(crotyl)Q-PhosCl (9) was found to be a superior catalyst to the other Q-Phos-based catalysts, and the reported in situ systems, in model coupling reactions involving 4-bromoanisole substrate with either N-methylaniline or 4-tert-butylbenzeneboronic acid. Precatalyst 9 also performed better than the catalysts bearing P(t-Bu)(2)(p-NMe(2)C(6)H(4)) ligand; however, it is comparable to the new crotyl catalysts bearing P(t-Bu)(3) or P(t-Bu)(2)Np ligands. In α-arylation of a biologically important model substrate, 1-tetralone, Pd(allyl)P(t-Bu)(2)(p-NMe(2)C(6)H(4))Cl (15) was found to be the best catalyst. The reason for the relatively higher activity of the crotyl complexes in comparison to the allyl derivatives in C-N bond formation reactions was investigated using X-ray crystallography in conjunction with NMR spectroscopic studies.

In α-Stellung arylierte Carbonyleinheiten sind in biologisch interessanten Molekulen haufig vertreten und daher von grosem Interesse fur die pharmazeutische Industrie. Die herkommlichen Syntheseverfahren fuhren bei der Aufskalierung haufig zu Problemen, z. B. wegen der Verwendung stochiometrischer Mengen an toxischen Reagentien und drastischer Reaktionsbedingungen. Im letzten Jahrzehnt wurden signifikante Fortschritte bei der Entwicklung alternativer Synthesewege unter milderen Bedingungen fur die metallkatalysierte α-Arylierung von Carbonylverbindungen erzielt. In diesem Aufsatz wird der aktuelle Stand dieses Gebietes zusammengefasst; dabei wird aufgezeigt, wie es gelang, die Substratbreite mithilfe geeigneter Herstellungsverfahren, z. B. durch Wahl der Liganden, Prakatalysatoren, Basen und Reaktionsbedingungen, zu erweitern.

Palladium-catalyzed cross-coupling reactions have emerged as an exceptionally powerful class of reactions for the creation of carbon–carbon and carbon–heteroatom bonds in both the academic and industrial sectors of research. This chapter provides a brief history, relevant background information and a preface to the important topics discussed in the remainder of the book.

The development and use of well-defined preformed Pd catalysts are reviewed from academic and industrial points of view. The strategies employed for the development of Pd precatalysts resulting in either L2Pd(0) or LPd(0) are discussed with examples from industry and academia on how the properties of the ligand and the nature of the precatalyst itself can precisely affect the efficiency of a number of cross-coupling reactions. The well-defined preformed Pd catalysts often improve the selectivity and activity of selected cross-coupling reactions by reducing the metal loading and the ligand-to-metal ratios. In addition, they are often more practical to handle than the corresponding in situ system containing a Pd precursor such as Pd(dba)x and a pyrophoric ligand such as t-Bu3P.

A wide range of aryl- and heteroaryl-chlorides and tosylates are converted to the corresponding amines.

In 2010, Richard Heck, Ei-ichi Negishi, and Akira Suzuki joined the prestigious circle of Nobel Laureate chemists for their roles in discovering and developing highly practical methodologies for C-C bond construction. From their original contributions in the early 1970s the landscape of the strategies and methods of organic synthesis irreversibly changed for the modern chemist, both in academia and in industry. In this Review, we attempt to trace the historical origin of these powerful reactions, and outline the developments from the seminal discoveries leading to their eminent position as appreciated and applied today.

Strategies for the development of Pd catalysts based on utilization of L2Pd and LPd species, beyond the contributions of the 2010 Nobel Laureates Richard Heck, Ei-ichi Negishi, and Akira Suzuki, along with their contemporaries, are reviewed. These well-defined, preformed Pd catalysts improve the selectivity and activity of selected cross-coupling reactions by reducing the metal loading and the ligand-to-metal ratios. This review describes predominantly the development of Pd precatalysts over the last 10 years and highlights the benefits often observed when using well-defined preformed catalysts relative to those generated in situ.

In 2010, Richard Heck, Ei-ichi Negishi, and Akira Suzuki joined the prestigious circle of Nobel Laureate chemists for their roles in discovering and developing highly practical methodologies for C-C bond construction. From their original contributions in the early 1970s the landscape of the strategies and methods of organic synthesis irreversibly changed for the modern chemist, both in academia and in industry. In this Review, we attempt to trace the historical origin of these powerful reactions, and outline the developments from the seminal discoveries leading to their eminent position as appreciated and applied today.

Various benzaldimines are arylated under mild reaction conditions using aryl trifluoroborates.

Mild and tolerant: A novel PdII‐catalyzed CH bond arylation with aryl‐BF3K salts transforms various electron‐deficient arenes under mild reaction conditions. Benzaldehydes are functionalized in the ortho position using a temporary imine directing group that controls the cyclopalladation. A broad range of benzaldimines are compatible with this process.

The air-stable complex Pd(η(3)-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(η(3)-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(η(3)-allyl)(DTBNpP)Cl precatalyst than the catalyst generated in situ from DTBNpP and Pd(2)(dba)(3) (100-140 °C, 2-5 mol % Pd). Other Pd(DTBNpP)(2)-based complexes, (Pd(DTBNpP)(2) and Pd(DTBNpP)(2)Cl(2)) were ineffective precatalysts under identical conditions for the amination reactions. Both Pd(DTBNpP)(2) and Pd(DTBNpP)(2)Cl(2) 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-Bu(3)P)(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, Pd(2)(DTBNpP)(2)(μ-Cl)(μ-allyl), was less active in comparison to [Pd(μ-Br)(TTBP)](2) and Pd(η(3)-allyl)(DTBNpP)Cl. The X-ray crystal structures of Pd(η(3)-allyl)(DTBNpP)Cl, Pd(DTBNpP)(2)Cl(2), Pd(DTBNpP)(2), and Pd(2)(DTBNpP)(2)(μ-Cl)(μ-allyl) are reported in this paper along with initial studies on the catalyst activation of the Pd(η(3)-allyl)(DTBNpP)Cl precatalyst.

Alpha-arylated carbonyl compounds are commonly occurring motifs in biologically interesting molecules and are therefore of high interest to the pharmaceutical industry. Conventional procedures for their synthesis often result in complications in scale-up, such as the use of stoichiometric amounts of toxic reagents and harsh reaction conditions. Over the last decade, significant efforts have been directed towards the development of metal-catalyzed alpha-arylations of carbonyl compounds as an alternative synthetic approach that operates under milder conditions. This Review summarizes the developments in this area to date, with a focus on how the substrate scope has been expanded through selection of the most appropriate synthetic method, such as the careful choice of ligands, precatalysts, bases, and reaction conditions.

We report a new Pd(II)-catalyzed C−H bond amination reaction to form carbazoles, an important motif that is prevalent in a range of systems. The catalytic amination process operates under extremely mild conditions and produces carbazole products in good to excellent yields. Carbazoles possessing complex molecular architecture can also be formed using this reaction, highlighting its potential in natural product synthesis applications. Preliminary mechanistic investigations reveal the reaction proceeds through a Pd(II)/Pd(IV) manifold and that reductive elimination from a high oxidation state Pd(IV) complex facilitates the mild conditions of this transformation.

We report a new Pd(II)-catalyzed C−H bond amination reaction to form carbazoles, an important motif that is prevalent in a range of systems. The catalytic amination process operates under extremely mild conditions and produces carbazole products in good to excellent yields. Carbazoles possessing complex molecular architecture can also be formed using this reaction, highlighting its potential in natural product synthesis applications. Preliminary mechanistic investigations reveal the reaction proceeds through a Pd(II)/Pd(IV) manifold and that reductive elimination from a high oxidation state Pd(IV) complex facilitates the mild conditions of this transformation.

16544 Background: We have shown that the high prevalence of HLA-A2 in Scandinavia is associated to poor prognosis in advanced (stage III-IV) serous adenocarcinoma of the ovary. Our objective was to...