There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-Induced Emission: Together We Shine, United We Soar!

Catalytic dehydrogenative cross-coupling: forming carbon-carbon bonds by oxidizing two carbon-hydrogen bonds

The site-selective formation of carbon-carbon bonds through direct functionalizations of otherwise unreactive carbon-hydrogen bonds constitutes an economically attractive strategy for an overall streamlining of sustainable syntheses. In recent decades, intensive research efforts have led to the development of various reaction conditions for challenging C-H bond functionalizations, among which transition-metal-catalyzed transformations arguably constitute thus far the most valuable tool. For instance, the use of inter alia palladium, ruthenium, rhodium, copper, or iron complexes set the stage for chemo-, site-, diastereo-, and/or enantioselective C-H bond functionalizations. Key to success was generally a detailed mechanistic understanding of the elementary C-H bond metalation step, which depending on the nature of the metal fragment can proceed via several distinct reaction pathways. Traditionally, three different modes of action were primarily considered for CH bond metalations, namely, (i) oxidative addition with electronrich late transition metals, (ii) σ-bond metathesis with early transition metals, and (iii) electrophilic activation with electrondeficient late transition metals (Scheme 1). However, more recent mechanistic studies indicated the existence of a continuum of electrophilic, ambiphilic, and nucleophilic interactions. Within this continuum, detailed experimental and computational analysis provided strong evidence for novel C-H bond metalationmechanisms relying on the assistance of a bifunctional ligand bearing an additional Lewis-basic heteroatom, such as that found in (heteroatom-substituted) secondary phosphine oxides or most prominently carboxylates (Scheme 1, iv). This novel insight into the nature of stoichiometric metalations has served as stimulus for the development of novel transformations based on cocatalytic amounts of carboxylates, which significantly broadened the scope of C-H bond functionalizations in recent years, with most remarkable progress being made in palladiumor ruthenium-catalyzed direct arylations and direct alkylations. These carboxylate-assisted C-H bond transformations were mostly proposed to proceed via a mechanism in which metalation takes place via a concerted base-assisted deprotonation. To mechanistically differentiate these intramolecular metalations new acronyms have recently been introduced into the literature, such as CMD (concerted metalationdeprotonation), IES (internal electrophilic substitution), or AMLA (ambiphilic metal ligand activation), which describe related mechanisms and will be used below where appropriate. This review summarizes the development and scope of carboxylates as cocatalysts in transition-metal-catalyzed C-H functionalizations until autumn 2010. Moreover, experimental and computational studies on stoichiometric metalation reactions being of relevance to the mechanism of these catalytic processes are discussed as well. Mechanistically related C-H bond cleavage reactions with ruthenium or iridium complexes bearing monodentate ligands are, however, only covered with respect to their working mode, and transformations with stoichiometric amounts of simple acetate bases are solely included when their mechanism was suggested to proceed by acetate-assisted metalation.

Carboxylate-assisted transition-metal-catalyzed C-H bond functionalizations: mechanism and scope.

The discovery of a concise route enabling site-selective arylation of polycyclic aromatic hydrocarbons (PAHs) with easily available aryl sources is an appealing yet challenging task toward the bottom-up preparation of π-extended PAHs. Disclosed herein is a palladium-catalyzed C8–H arylation of 1-naphthoic acid derivatives with aryl iodides in a low reactant molar ratio via an electrophilic aromatic substitution (SEAr) process. In addition, a C8–H annulation protocol is developed to rapidly assemble benzanthrones by simply switching the solvent to 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP).

Palladium-catalyzed C8–H arylation and annulation of 1-naphthalene carboxylic acid derivatives with aryl iodides

A simple copper salt catalyzed N-arylation reaction with arylboronic acids is reported. In the presence of a catalytic amount of a simple copper salt, the coupling of arylboronic acids with imides was performed in MeOH to give N-arylimides in excellent yields: a variety of amines, amides and sulfonamides could also be successfully coupled with arylboronic acids to give cot-responding N-arylated products in moderate yields.

A Simple Copper Salt Catalyzed N‐Arylation of Amines, Amides, Imides, and Sulfonamides with Arylboronic Acids.

Palladium-Catalyzed Cascade Dearomative Spirocyclization and C-H Annulation of Aromatic Halides with Alkynes.

Palladium-catalyzed denitrative Sonogashira-type cross-coupling of nitrobenzenes with terminal alkynes.

Protected α-amino epoxides were successfully obtained in high threo-selectivity (up to 99%) under mild reaction conditions by using carbonyl 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin ruthenium(II) [Ru(TDCPP)CO] as catalyst and 2,6-dichloropyridine N-oxide (Cl2PyNO) as oxidant.

Highly diastereoselective epoxidation of protected α-amino alkenes catalyzed by ruthenium porphyrin/Cl2PyNO system

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