One of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense exploration and commercialization of new polymerization technologies based on single-site and metallocene coordination olefin polymerization catalysts.1 The vast number of specifically designed/synthesized transition metal complexes (catalyst precursors) and main-group organometallic compounds (cocatalysts) allows unprecedented control over polymer microstructure, the generation of new polymer architectures, and the development of new polymerization reactions. Commercialization of new generations of single-site and metallocene catalyst-based technologies has provided the multibillion pound per year polyolefins industry with the ability to deliver a wide range of new and innovative olefin-based polymers having improved properties.2-4 The intense industrial activity in the field and the challenges to our basic understanding that have come to light have in turn 1391 Chem. Rev. 2000, 100, 1391−1434

/pdf/cocatalysts-for-metal-catalyzed-olefin-polymerization-37a9jvjiei.pdf

Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure−Activity Relationships

Isolation and synthesis of biologically active carbazole alkaloids

Nanographenes, or extended polycyclic aromatic hydrocarbons, have been attracting renewed and more widespread attention since the first experimental demonstration of graphene in 2004. However, the atomically precise fabrication of nanographenes has thus far been achieved only through synthetic organic chemistry. The precise synthesis of quasi-zero-dimensional nanographenes, i.e. graphene molecules, has witnessed rapid developments over the past few years, and these developments can be summarized in four categories: (1) non-conventional methods, (2) structures incorporating seven- or eight-membered rings, (3) selective heteroatom doping, and (4) direct edge functionalization. On the other hand, one-dimensional extension of the graphene molecules leads to the formation of graphene nanoribbons (GNRs) with high aspect ratios. The synthesis of structurally well-defined GNRs has been achieved by extending nanographene synthesis to longitudinally extended polymeric systems. Access to GNRs thus becomes possible through the solution-mediated or surface-assisted cyclodehydrogenation, or “graphitization,” of tailor-made polyphenylene precursors. In this review, we describe recent progress in the “bottom-up” chemical syntheses of structurally well-defined nanographenes, namely graphene molecules and GNRs.

/pdf/new-advances-in-nanographene-chemistry-1qv0crgf8s.pdf

New advances in nanographene chemistry

2.3. [4 + 4] Cycloadditions 1058 2.4. Photocycloadditions of Aromatic Compounds 1058 2.4.1. Benzene Derivatives 1058 2.4.2. Condensed Aromatic Compounds 1060 3. Photochemical Rearrangements 1061 4. Cyclizations 1064 4.1. Pericyclizations 1064 4.2. Norrish−Yang Reaction 1066 5. Photochemical Extrusion of Small Molecules 1067 6. Photochemical Electron Transfer 1068 6.1. Photochemical Electron-Transfer Reactions with a Catalytic Sensitizer 1068

Photochemical Reactions as Key Steps in Organic Synthesis

The palladium-catalyzed coupling of haloarenes and haloalkenes with alkenes, which was discovered by Richard F. Heck in the late sixties, has been a topic of fluctuating interest; however, in the last six years activity in this area has flourished. Careful choice of substrates and skillful tailoring of reaction conditions lead to impressive sequences consisting of even different reaction types that occur not only in a consecutive mode, but also in a single operation. The wellestablished Heck reaction, together with other mechanistically related palladiumcatalyzed transformations with arene, alkene, and alkyne derivatives, opens the door to a tremendous variety of elegant and highly convergent routes to structurally complex molecules. The reaction is not disturbed by heteroatoms such as oxygen and nitrogen (nor by sulfur and phosphorus with some limitations). The spectrum of recent achievements starts with a range of chemoselective and regioselective monocouplings of highly functionalized substrates with unsymmetrical and multisubstituted reaction partners. Other advances include cascade reactions in which three, four, five, and even eight new CC bonds are formed to yield oligofunctional and oligocyclic products with impressive molecular complexity. Even the enantioselective construction of complex natural products with quaternary stereocenters has been achieved with Heck reactions in key steps, as exemplified by the synthesis of crinan, picrotoxinin, and morphine. Today, the Heck reaction is indispensible in the arsenal of synthetic methods available to organic chemists. Certainly it is only a matter of time before the Heck reaction is applied in industrial syntheses.

Fine Feathers Make Fine Birds: The Heck Reaction in Modern Garb†

Ring-slippage chemistry of transition metal cyclopentadienyl and indenyl complexes

rotation,I0 spectrophot~metry,~~~~-~~ circular dichroism,I5 fluorescen~e,’~ NMR,16 temperature jump,’*J7 and v i s c ~ m e t r y . ~ ~ J ~

Surreptitious involvement of a metallacycle substituent in metal-mediated alkyne cleavage chemistry

Modern Rhodium-Catalyzed Organic Reactions

Synthesis of electrophilic (dimethylcarbene)iron complexes

[2 + 2 + 1] Alkyne Cyclotrimerizations: A Metallacyclopentadiene Route to Fulvenes

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