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Palladium Catalyzed Aerobic Oxidative Cyclization of ortho Vinylanilines with Isocyanides

Palladium Catalyzed Aerobic Oxidative Cyclization of ortho Vinylanilines with Isocyanides

Based on the preliminary mechanistic investigation, we propose the following mechanism for the palladium catalyzed aerobic oxidative cyclization (Scheme 6). Palladium complex A, formed from Pd(OAc) 2 and isocyanide, reacts with amine in the presence of base to form complex B. Formation of palladium species C from B can be explained through the insertion of isocyanide onto Pd-N bond. β-Hydride elimination from C would generate intermediate carbodiimide E and complex D. Reductive elimination of acid from D afford the Pd(0) species, which on oxidation with molecular oxygen and acid would regenerate the catalytically active species A. On the other hand, carbodiimide E undergoes Pd-assisted thermal 6 π -electrocyclization to afford cyclized compound F followed by [1,7]-H shift would furnish the expected 2-aminoquinolines 3.

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Part I: Chemoselective Palladium Catalyzed Reactions of Bifunctional 2-B(pin)-Substituted Allylic Acetate Derivatives Part II: Palladium Catalyzed Deprotonative Arylation of Azaarylmethyl Amines and Ethers

Part I: Chemoselective Palladium Catalyzed Reactions of Bifunctional 2-B(pin)-Substituted Allylic Acetate Derivatives Part II: Palladium Catalyzed Deprotonative Arylation of Azaarylmethyl Amines and Ethers

coupling reaction conditions in entry 13 of Table 2.4 with aryl iodides and bromides. The 2- B(pin)-substituted allylic benzoate 2.7a underwent cross-coupling with iodobenzene to furnish the 2-aryl substituted allylic benzoate 2.9a in 96% yield (Table 2.7, entry 1). Bromobenzene, on the other hand, resulted in low yield of the cross-coupled product 2.9a (38%), with multiple byproducts (entry 2). The palladium catalyst likely activates the allylic benzoate in the presence of less reactive bromobenzene. Electron deficient aryl halides are known to undergo oxidative addition more rapidly than analogous electron rich aryl halides. 33 With 4-trifluoromethyl bromobenzene and allylic benzoate 2.7a the cross-coupled product 2.9b was isolated in 76% yield (entry 3). The 2-B(pin)-substituted allylic carbonates 2.8a and 2.8b underwent cross- coupling with both aryl iodides and electron deficient bromides to furnish the 2-arylated allylic carbonates 2.9c–f in 57–91% yield (entries 4–8). These results demonstrate that the palladium catalyst preferentially oxidatively adds aryl iodides and bromides over 1,3-dialkyl-substituted 2- B(pin) allylic benzoates and carbonates. However, more reactive 1-phenyl-2-B(pin)-substituted allylic benzoate 2.7b and carbonate 2.8c were decomposed and no cross-coupling product was observed (entries 9 and 10).

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Palladium Catalyzed Decarboxylative and Decarbonylative Transformations in the Synthesis of Fine and Commodity Chemicals

Palladium Catalyzed Decarboxylative and Decarbonylative Transformations in the Synthesis of Fine and Commodity Chemicals

The Stoltz laboratory has established a palladium-catalyzed enantioselective decarboxylative allylic alkylation of β-keto esters for the synthesis of α-quaternary ketones since 2005. Recently, we extended this chemistry to lactams due to the ubiquity and importance of nitrogen-containing heterocycles. A wide variety of α-quaternary and tetrasubstituted α-tertiary lactams were obtained in excellent yields and exceptional enantioselectivities using our palladium-catalyzed decarboxylative allylic alkylation chemistry. Enantioenriched α-quaternary carbonyl compounds are versatile building blocks that can be further elaborated to intercept synthetic intermediates en route to many classical natural products. Thus our chemistry enables catalytic asymmetric formal synthesis of these complex molecules.

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The Design and Development of Palladium Catalyzed Aerobic Oxidative Transformations

The Design and Development of Palladium Catalyzed Aerobic Oxidative Transformations

Zhang, Dave Ebner, Dan Caspi, Ryan McFadden, Toyoki Nishimata, and JT Mohr. Although I never worked directly with anyone at any given time on this project, I know this project would be nothing without all of their efforts. Jeff has done an excellent job in developing the oxidative kinetic resolution beyond the initial work. Raissa has done some of the most profound work on the palladium chemistry while I’ve been here. I have a great deal of respect for her skills in experimental design and execution. Haiming came in and cranked on the C-H bond functionalization chemistry. God, he runs a ton of reactions. I love that. I think his efforts have really helped to outline where the project needs to go in the future. Dave and Toyoki have both started working on non-sparteine- based systems. I’m happy to see that people are excited about taking the chemistry in this direction, despite how difficult it may be, and I wish them the best. I really admire their willingness to work on projects that can be challenging, but could eventually lead to some thrilling outcomes. I think that although there’s still a bunch to be done, the project has come a long way in a pretty short amount of time. I have tried to point out their specific contributions in the text of the thesis, but I wanted to thank them collectively here as well.

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Palladium catalyzed α arylation of arylketones at low catalyst loadings

Palladium catalyzed α arylation of arylketones at low catalyst loadings

Palladium-catalyzed bond forming reactions are nowadays one of the most common tools synthetic chemists employ, in industry as well as in academia. [1] Enormous resources have been directed into the development of efficient methodologies to perform this class of transformations in an environmentally and economically advantageous manner. In the last two decades, the design of electron-rich, bulky ligands, has addressed many challenges in this field, allowing the coupling of highly unactivated coupling partners under mild conditions and using low catalyst loadings. [2] The -arylation of ketones, simultaneously disclosed by Buchwald and Hartwig, [3] is potentially one of the most powerful and atom-economical C-C bond formation as it uses simple and widely available substrates and generates a minimum amount of side-products; the general reaction mechanism is depicted in Figure 1. [4]

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Development and Applications of the Palladium Catalyzed Enantioselective Oxidation of Secondary Alcohols

Development and Applications of the Palladium Catalyzed Enantioselective Oxidation of Secondary Alcohols

vi I also have to express my gratitude for my other project mates over the years. Professor Eric Ferreira is one of the most amazing, hardworking chemists I have known. He had a hand in getting most of the palladium oxidation projects going in the lab. Dr. Jeff Bagdanoff and Raissa were also instrumental in the oxidative kinetic resolution project, as many of their studies led to my successes in the lab. Dr. Shyam Krishnan was also indirectly on the alcohol oxidation project. He had many helpful chemistry suggestions and put an incredible amount of work to get the big paper on our syntheses of alkaloids out the door. Collaborating with Dr. Zoltán Novák, a postdoctoral scholar in the Stoltz lab, on the kinetic resolution / Claisen chemistry was a very rewarding experience, both personally and scientifically. Our collaborator at the University of York, Professor Peter O’Brien, has been very generous in sending along the latest diamine ligand from his group for us to test in the resolution, and I am happy that our combined efforts were ultimately very fruitful. Dr. Uttam Tambar was a great project mate for the amurensinine research. He taught me a lot about total synthesis and dealing with frustration with a project, and chatting with him my first year was really what convinced me that the Stoltz lab was the place to be.

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Effectual Direct Synthesis of Diversely Substituted 4- aryl/alkyl Coumarins by Palladium Catalyzed Oxidative Suzuki–Miyaura Coupling Jaydip Rajpara, Arpit Radadia, Yogesh Naliapara*

Effectual Direct Synthesis of Diversely Substituted 4- aryl/alkyl Coumarins by Palladium Catalyzed Oxidative Suzuki–Miyaura Coupling Jaydip Rajpara, Arpit Radadia, Yogesh Naliapara*

In conclusion, we have developed an efficient protocol for the synthesis of 4-aryl/alkyl coumarins via palladium-catalyzed oxidative Suzuki-Miyaura coupling reaction of coumarins and diversely substituted boronic acids (Table-3). The reaction represents a convenient, atom-economic approach with good functional group tolerance. Pd(PPh 3 ) 4 is not suitable catalyst for this

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Han, Wei
  

(2011):


	Iron and Palladium Catalyzed C-H Functionalization.


Dissertation, LMU München: Fakultät für Chemie und Pharmazie

Han, Wei (2011): Iron and Palladium Catalyzed C-H Functionalization. Dissertation, LMU München: Fakultät für Chemie und Pharmazie

The formation of new carbon–carbon bonds is the most important transformation in organic chemistry. 1 Transition metal catalyzed activation of C(sp 3 )–H bonds and subsequent C–C bond formation which avoids the use of prefunctionalized starting material is therefore a valuable and straightforward synthetic strategy. 2–4 In contrast to many toxic and/or rare metals previously used for this transformation, iron is ubiquitous in the geosphere with 4.7% wt abundance and in the biosphere where it is often found as part of catalytic systems. Consequently, in recent years iron catalysts have been used for a multitude of organic syntheses, including oxidations and cross couplings. 5 So far, C–C bond forming reactions via iron catalyzed functionalization of C(sp 3 )–H bonds generally require elevated temperatures (60 to 100 o C), 6–9 and there are few literature reports on iron-based system sufficiently active to catalyze C(sp 3 )–H cross couplings at room temperature. 10,15

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How Language Policies and Practices Affect Classrooms in Schools and Colleges

How Language Policies and Practices Affect Classrooms in Schools and Colleges

In addition, 18 F–Labeled compounds are indispensable as radionuclides in radiotracers for positron emission tomography (PET). These unique properties make the introduction of fluorine to bioactive molecules intriguing. The construction of C–F bonds is very challenging, 27,28 particularly in a selective late stage synthesis. However, recently there have been advances in ortho directed palladium catalyzed electrophilic fluorination of arenes via C–H activation. 28 In 2006 Sanford used 8–methylquinolines and phenyl–pyridines to accomplish this transformation in acceptable yields and under microwave

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Photoredox-Mediated Metal-Free C–h Alkylation And Dual Catalysis

Photoredox-Mediated Metal-Free C–h Alkylation And Dual Catalysis

Our group became interested in photoredox catalysis as a tool to generate alkyl radicals for use in cross-coupling reactions. In 2014, we disclosed the first example of photoredox/Ni dual catalysis to forge C(sp 2 )–C(sp 3 ) bonds under unusually mild reaction conditions. 7 In this transformation, photoredox/Ni dual catalysis proceeds via the single-electron oxidative fragmentation of radical precursors and alkyl radical addition to a nickel catalyst, a process we refer to as single-electron transmetalation (Figure 1.4). The addition of the radical to the nickel complex using this protocol is the synthetic equivalent of the more traditional two-electron transmetalation, and the activation energy for this process is extraordinarily low. 8 This paradigm is in stark contrast to typical Pd- or Ni-catalyzed processes, where transmetalation from an organometallic nucleophile to a metal center is often the rate-determining step with a high energy of activation. 9

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Pd Catalyzed Microwave Irradiated Regioselective Aroylation Reaction of Crotyl  and Allyltrifluoroborates

Pd Catalyzed Microwave Irradiated Regioselective Aroylation Reaction of Crotyl and Allyltrifluoroborates

An interesting regioselectivity is observed when the mixture of potassium crotyltrif- luoroborate (1a) and aroyl chlorides having electron-deficient and electron-rich groups is microwaved in the presence of palladium-catalyst. In the case of electron withdrawing group with phenyl ring of aroyl chlorides, isomerized α , β -unsaturated compound 3 is the product whereas electron donating group with phenyl ring of aroyl chlorides furnishes α -adduct 4. Similar aroylation reaction is also established for potassium allyltrifluoroborate (1b). In this case, regioselectivity is unaffected with changing electron-rich or electron-deficient groups in phenyl ring of the aroyl chlo- rides. Reactions proceed with, essentially in same rate, affording the corresponding aryl propenyl ketones (crotonophenones) 5 in good to high yields.

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A Novel Synthesis of [4-(3-Methyl-1H-Indol-2-Yl)Phenyl]Phenylmethanone

A Novel Synthesis of [4-(3-Methyl-1H-Indol-2-Yl)Phenyl]Phenylmethanone

In this research work, the target molecule containing a diphenyl methanone moiety and methyl group at positions 2 and 3 respectively was synthesized. The product was obtained in good yield whereas the yield of the 2-substituted product namely [4-(1H-indol-2-yl)phenyl](phenyl) methanone which was prepared 18 by the palladium

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Thiopseudourea Ligated Palladium(II) Complexes: Synthesis, Characterization and Application as Catalysts for C-C Coupling and Heteroannulation Reactions

Thiopseudourea Ligated Palladium(II) Complexes: Synthesis, Characterization and Application as Catalysts for C-C Coupling and Heteroannulation Reactions

Abstract homogeneous catalysis and the necessity to design and develop the phosphine-free ligands for palladium catalysis. The properties and structures of the ligands like phosphine and phosphine-free (N- heterocyclic carbenes, carbocyclic carbenes) N-donor ligands are discussed to familiarize the ligands used for the development of homogeneous catalysts.

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Applications of Palladium-Catalyzed Enantioselective Decarboxylative Alkylation in Natural Products Total Synthesis

Applications of Palladium-Catalyzed Enantioselective Decarboxylative Alkylation in Natural Products Total Synthesis

The enantioselective generation of all-carbon quaternary stereocenters is a challenge for the modern organic chemist. 1 A recent tool added to the arsenal of methods in this field has been palladium-catalyzed decarboxylative alkylation. 2 This method has allowed for the preparation of diverse cyclic α-quaternary allyl ketones and vinylogous esters, with high functional group tolerance. Recently, we developed three methods for generating enantioenriched α-quaternary ketones in the presence of a Pd(0) source and a chiral phosphinooxazoline ligand. The first two methods utilize silyl enol ether and enol carbonate substrates, respectively, 3 while the third method employs racemic allyl β - ketoesters. 4 Since the enantioenriched products prepared are well suited for further synthetic elaboration, we sought to advance them to intermediates reported in total syntheses of classic molecules. Herein we disclose catalytic enantioselective formal syntheses of an array of challenging natural products bearing at least one all-carbon quaternary stereocenter.

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ORGANIC TRANSFORMATIONS CATALYZED BY PROLINE AND ITS DERIVATIVES

ORGANIC TRANSFORMATIONS CATALYZED BY PROLINE AND ITS DERIVATIVES

synthesis of a plethora of biologically and pharmaceutically important selenium compounds such as selenium salts, selenoxides, selenimines and selenide dihalides. In the past five years there has been resurgence in interest in developing mild synthetic methods based on the copper catalysts as an alternative to palladium (0) catalysts for the formation of aryl-carbon and aryl-heteroatom bonds.

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Manipulating Selectivity and Reactivity in Palladium-Catalyzed Oxidation Reactions

Manipulating Selectivity and Reactivity in Palladium-Catalyzed Oxidation Reactions

Given the unusual reactivity of the nitrite-modified Wacker oxidation and the complexity of the catalytic system comprised of several co-catalytic species, we conducted a series of experiments aiming to deconvolute the roles of the reaction components. As copper salts are commonly employed as redox- catalysts in Wacker-type oxidations, 16 it was not surprising that removal of copper from the process provided only traces of products. Exposure of alkene to stoichiometric palladium and silver nitrite, however, also provided sluggish oxidation rates and poor selectivity. An analogous reaction was conducted with stoichiometric palladium in the absence of copper salts under Tsuji–Wacker conditions and, as expected, product was rapidly formed. These results clearly implicate copper as having a more intimate role than as a simple redox catalyst for palladium. To confirm the mechanistic necessity of the palladium salt for product formation, stoichiometric copper dichloride and silver nitrite (no palladium) were subjected to the alkene but provided no conversion. Thus, it appears that both palladium and copper are crucial metals for mechanistic steps prior to product formation.

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Visible light promoted Fe catalyzed C(sp2) C(sp3) Kumada cross coupling in flow

Visible light promoted Fe catalyzed C(sp2) C(sp3) Kumada cross coupling in flow

Abstract: A continuous-flow, visible-light-promoted method has been developed to overcome the limitations of iron- catalyzed Kumada–Corriu cross-coupling reactions. A variety of strongly electron rich aryl chlorides, previously hardly reactive, could be efficiently coupled with aliphatic Grignard reagents at room temperature in high yields and within a few minutes residence time, considerably enhancing the applic- ability of this iron-catalyzed reaction. The robustness of this protocol was demonstrated on a multigram scale, thus provid- ing the potential for future pharmaceutical application.

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Part A: Palladium(II)-Catalyzed Enantioselective Saucy-Marbet Claisen Rearrangement of Propargyloxy indoles to Quaternary Oxindoles and Spirocyclic Lactones. Part B: The Regioselective Oxidative Coupling of Phenols .

Part A: Palladium(II)-Catalyzed Enantioselective Saucy-Marbet Claisen Rearrangement of Propargyloxy indoles to Quaternary Oxindoles and Spirocyclic Lactones. Part B: The Regioselective Oxidative Coupling of Phenols .

Trost, B. M.; Czabaniuk, L. C. “Palladium-Catalyzed Asymmetric Benzylation of 3-Aryl Oxindoles” J. Am. Chem. Soc. 2010, 132, 15534-15536. (b) Han, Y.-Y.; Wu, Z.-J.; Chen, W.-B.; Du, X.-L.; Zhang, X.-M.; Yuan, W.-C. “Diastereo- and Enantioselective Conjugate Addition of 3-Substituted Oxindoles to Nitroolefins Catalyzed by a Chiral Ni(OAc)2-Diamine Complex under Mild Conditions” Org. Lett. 2011, 13, 5064-5067. (c) Ding, M.; Zhou, F.; Liu, Y. L.; Wang, C. H.; Zhao, X. L.; Zhou, J. “Cinchona Alkaloid-based Phosphoramide Catalyzed Highly Enantioselective Michael Addition of Unprotected 3-Substituted Oxindoles to Nitroolefins” Chem. Science 2011, 2, 2035-2039. (d) Wang, Y.; Liu, L.; Zhang, T.; Zhong, N. J.; Wang, D.; Chen, Y. J. “Diastereo- and Enantioselective [3+2] Cycloaddition Reaction of Morita-Baylis-Hillman Carbonates of Isatins with N-Phenylmaleimide Catalyzed by Me-DuPhos” J. Org. Chem. 2012, 77, 4143-4147.

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Carbene Based Palladium-catalyzed Mizoroki-Heck Reaction

Carbene Based Palladium-catalyzed Mizoroki-Heck Reaction

1. (a.)Trost, B.M.; Verhoeven, T.R. Organopalladium Compounds in Organic Synthesis and in Catalysis. In Comprehensive Organometallic Chemistry. Wilkinson, G., Stone, F.G.A., Abel, E.W., Eds.; Pergamon: Oxford, UK; 8: 799-938 (1982). (b) Miyaura, N.; Suzuki, A. Palladium- Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 95: 2457-2483 (1995).

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Studies in Palladium-Catalyzed Allylic Alkylation: Enantioselective Total Syntheses of Structurally Diverse Alkaloids

Studies in Palladium-Catalyzed Allylic Alkylation: Enantioselective Total Syntheses of Structurally Diverse Alkaloids

The successful development of a novel substrate class for palladium-catalyzed allylic alkylation, namely dihydropyrido[1,2-a]indolones (DHPIs), has enabled divergent syntheses of multiple monoterpene indole alkaloids. By setting the C20 quaternary stereocenter present within these alkaloids at an early stage in the synthesis, the remaining stereocenters can be forged with exquisite levels of control. Critical to the success of this work was the identification of highly tunable and predictable cyclizations between an indole and a C2-tethered iminium moiety. Regiodivergent cyclizations were used to complete the first catalytic enantioselective total synthesis of (–)-goniomitine, along with efficient formal syntheses of (+)-aspidospermidine and (–)-quebrachamine. Stereodivergent cyclization strategies were then employed in total syntheses of (+)- limaspermidine and (+)-kopsihainanine A. Synthetic efforts toward the highly caged Kopsia alkaloids (–)-kopsinine, (–)-kopsinilam, and (–)-kopsifoline G are also discussed.

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