Structural Characteristics of Carbon Nanofibers for On-chip Interconnect Applications

In this letter, we compare the structures of plasma-enhanced chemical vapor deposition of Ni-catalyzed and Pd-catalyzed carbon nanofibers (CNFs) synthesized for on-chip interconnect applications with scanning transmission electron microscopy (STEM). The Ni-catalyzed CNF has a conventional fiberlike structure and many graphitic layers that are almost parallel to the substrate at the CNF base. In contrast, the Pd-catalyzed CNF has a multiwall nanotubelike structure on the sidewall spanning the entire CNF. The microstructure observed in the Pd-catalyzed fibers at the CNF-metal interface has the potential to lower contact resistance significantly, as our electrical measurements using current-sensing atomic force microscopy indicate. A structural model is presented based on STEM image analysis

Palladium-catalyzed acetylation of arenes.

A simple method for the preparation of aryl methyl ketones is reported. The transformation involves the Pd-catalyzed coupling of an acyl anion equivalent, acetyltrimethylsilane, with aryl bromides to afford the corresponding acetylated arenes in synthetically useful yields. The methodology is tolerant of heterocycles and provides a new method for arene functionalization

Pd-catalyzed enantioselective aerobic oxidation of secondary alcohols: Applications to the total synthesis of alkaloids

Enantioselective syntheses of the alkaloids (-)-aurantioclavine, (+)-amurensinine, (-)-lobeline, and (-)- and (+)-sedamine are described. The syntheses demonstrate the effectiveness of the Pd-catalyzed asymmetric oxidation of secondary alcohols in diverse contexts and the ability of this methodology to set the absolute configuration of multiple stereocenters in a single operation. The utility of an aryne C-C insertion reaction in accessing complex polycyclic frameworks is also described

Application of Novel Phosphine Ligands in Palladium-Catalyzed Cross-Coupling Reactions

This thesis describes the application of 2-phosphino-N-aryl-heterocycles as ligands in Pd-catalyzed C–C, C–N and C–O bond forming reactions. Based on prior studies, 2-phosphino-N-arylindoles and -pyrrols were found to form efficient catalysts with Pd-salts in the Sonogashira coupling of (hetero)aryl bromides and the Pd-catalyzed monoarylation of ammonia. The novel imidazole-based phosphines were prepared after a modular synthesis and are stable towards air. They were employed in the Pd-catalyzed phenol synthesis, the Heck-Cassar coupling, and the Pd-catalyzed monoarylation of ammonia. Furthermore, mechanistic studies in the Pd-catalyzed hydroxylation were undertaken.In der vorliegenden Dissertation wird die Anwendung von Dialkyl-heteroarylphosphinen als Liganden in palladiumkatalysierten Bindungsknüpfungen beschrieben. Die zuvor beschriebenen Indol- und Pyrrolphosphine wurden erfolgreich in der Sonogashira-Kupplung von Arylbromiden und in der Anilinsynthese eingesetzt. Die neuartigen Imidazolderivate konnten mit einer modularen Synthesemethode dargestellt werden. Mit auf ihnen basierenden Palladium-Katalysatoren konnten Arylhalide effizient sowohl mit Alkinen, als auch mit Wasser und Ammoniak umgesetzt werden. Des weiterten wurden mechanistische Untersuchungen in der palladiumkatalysierten Phenolsynthese durchgeführt

Triazole-Directed Pd-Catalyzed C(sp2)–H Oxygenation of Arenes and Alkenes

Selective Pd-catalyzed C(sp2)–H oxygenation of 4-substituted 1,2,3-triazoles is described. Unlike previous metal-catalyzed C–H functionalization events, which preferentially occur at the activated heterocyclic C–H bond, the regioselective oxygenation of the arene/alkene moiety is now achieved featuring the unconventional role of a simple triazole scaffold as a modular and selective directing group.MINECO for a Ramon y Cajal research contract (RYC-2012-09873)

Selective C(sp2)−H Halogenation of "click" 4-Aryl-1,2,3-triazoles

Selective bromination reactions of “click compounds” are described. Electron-neutral and electron-deficient arenes selectively undergo unprecedented Pd-catalyzed C–H ortho-halogenations assisted by simple triazoles as modular directing groups, whereas electron-rich arenes are regioselectively halogenated following an electrophilic aromatic substitution reaction pathway. These C–H halogenation procedures exhibit a wide group tolerance, complement existing bromination procedures, and represent versatile synthetic tools of utmost importance for the late-stage diversification of “click compounds”. The characterization of a triazole-containing palladacycle and density functional theory studies supported the mechanism proposal.We are grateful to Gobierno Vasco (ELKARTEK_KK-2015/0000101; IT_1033-16) and UPV/EHU (GIU15/31) for financial support. A. C. thanks MINECO for a Ramón y Cajal research contract (RYC-2012-09873). Cost-CHAOS action is also acknowledged

A regioselectivity switch in Pd-catalyzed hydroallylation of alkynes.

By exploiting the reactivity of a vinyl-Pd species, we control the regioselectivity in hydroallylation of alkynes under Pd-hydride catalysis. A monophosphine ligand and carboxylic acid combination promotes 1,5-dienes through a pathway involving isomerization of alkynes to allenes. In contrast, a bisphosphine ligand and copper cocatalyst favor 1,4-dienes via a mechanism that involves transmetalation. Our study highlights how to access different isomers by diverting a common organometallic intermediate

Influence of Catalyst Structure and Reaction Conditions on anti ‐ versus syn ‐Aminopalladation Pathways in Pd‐Catalyzed Alkene Carboamination Reactions of N ‐Allylsulfamides

The Pd‐catalyzed coupling of N ‐allylsulfamides with aryl and alkenyl triflates to afford cyclic sulfamide products is described. In contrast to other known Pd‐catalyzed alkene carboamination reactions, these transformations may be selectively induced to occur by way of either anti ‐ or syn ‐aminopalladation mechanistic pathways by modifying the catalyst structure and reaction conditions. A constructive approach : A concise, efficient approach has led to the synthesis of cyclic sulfamides by using Pd‐catalyzed alkene carboamination reactions of N ‐allylsulfamides (see picture; OTf=triflate, RuPhos=2‐dicyclohexylphosphino‐2′,6′‐diisopropoxybiphenyl, X‐phos=2‐dicyclohexylphosphino‐2′,4′,6′‐triisopropylbiphenyl). The mechanism of these transformations is highly dependent on the catalyst structure and reaction conditions. The reactions can be induced to proceed selectively through either syn ‐ or anti ‐aminopalladation pathways under appropriate conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107505/1/chem_201402258_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/107505/2/8782_ftp.pd

Development and applications of highly selective palladium-catalyzed monocoupling reactions of (cyclo)alkenes and 1,3-alkadienes bearing two or three electrophilic sites and bis(enol triflates) with terminal alkynes

The motivation for writing this review with 558 references, which covers the literature up to the end of September 2012, is to fill a part of this gap by illustrating highly selective Pd/Cu-catalyzed and Cu-free Pd-catalyzed monoalkynylation reactions of (cyclo)alkenes and 1,3-butadienes bearing two or three identical or different electrophilic sites and bis(enol triflates) with terminal alkynes. However, Pd-catalyzed selective monocoupling reactions of 1-alkynes with (hetero)aryl halides or pseudohalides with two identical or different electrophilic sites will not be covered. Moreover, Pd-catalyzed monocoupling reactions of 1-alkynes with non-conjugated diene systems bearing an electrophilic site on each carbon–carbon double bond have also been considered to be beyond the scope of this review. In addition to describing and commenting on the aforementioned monoalkynylation reactions of (cyclo)alkenes and 1,3-dienes with two or three identical or different electrophilic sites and bis(enol triflates), emphasis has been placed on the use of Pd-catalyzed monoalkynylations of (cyclo)alkenes and 1,3-butadienes bearing two or three identical or different electrophilic sites and bis(enol triflates) as key steps of the syntheses of core structures and models of enediyne antitumor antibiotics, pharmacologically active compounds, and bioactive naturally occurring compounds including insect sex pheromone components, and fungal and plant metabolites. Moreover, the review has been focused on the formation of disubstituted acetylenic derivatives by one-pot site-selective Pd-catalyzed consecutive alkynylation reactions of di(pseudo)halogenated olefinic substrates with two different terminal alkynes. Where appropriate, the reasons for the observed stereo-, site-, and/or chemoselectivities of the reported Sonogashira-type monoalkynylation reactions have been mentioned and discussed