Molecular Engineering of Chalcogen-Embedded Anthanthrenes via peri-Selective C-H Activation: Fine-Tuning of Crystal Packing for Organic Field-Effect Transistors.

Disclosed herein is a RhCl3 -catalyzed peri-selective C-H/C-H oxidative homo-coupling of 1-substituted naphthalenes, which provides a highly efficient and streamlined approach to chalcogen-embedded anthanthrenes from readily available starting materials. Introducing O, S, and Se into the anthanthrene skeleton leads to gradually increased π-π stacking distances but significantly enhanced π-π overlaps with the growth of the hetero-atom radius. Moderate π-π distance, overlap area, and intermolecular S-S interactions endow S-embedded anthanthrene (PTT) with excellent 2D charge-transport properties. Moreover, the transformation of p-type to n-type S-embedded anthanthrenes is realized for the first time via the S-atom oxidation from PTT to PTT-O4. In organic field-effect transistor devices, PTT derivatives exhibit hole transport with mobilities up to 1.1 cm2  V-1 s-1 , while PTT-O4 shows electron transport with a mobility of 0.022 cm2  V-1 s-1 .

Copper-Catalyzed anti-Selective Radical 1,2-Alkylarylation of Terminal Alkynes.

A copper-catalyzed highly anti-selective radical 1,2-alkylarylation of terminal alkynes with aryl boronic acids and alkyl bromides has been established. The reaction exhibits high compatibility with a wide range of terminal alkynes and diverse aryl boronic acids, thus providing facile access to various stereodefined trisubstituted alkenes in high yield under mild reaction conditions. Preliminary mechanistic investigations support the formation of alkyl radicals and their subsequent addition to alkynes in the reaction.

Four Types of CdTe Magic-Size Clusters from One Prenucleation Stage Sample at Room Temperature.

Four types of colloidal semiconductor CdTe magic-size clusters (MSCs), each of which is in a single-ensemble form, have been obtained at room temperature from a single induction period (IP) sample in dispersion. The induction period is the prenucleation stage that occurs prior to nucleation and growth of colloidal quantum dots (QDs). Three types display sharp optical absorption peaking at either 371, 417, or 448 nm, and the fourth type exhibits a sharp absorption doublet with peaks at 350 and 371 nm. These MSCs are respectively denoted as sMSC-371, sMSC-417, sMSC-448, and dMSC-371. We show that the evolution of the various MSCs is affected by the nature of their dispersions. We hypothesize that the evolution of MSCs involves their precursor compounds (PCs), which are transparent in optical absorption. The present study explores new avenues for the exclusive synthesis of four types of CdTe MSCs (with each in a single-ensemble form) and provides an improved understanding for their formation.

Precursor Self-Assembly Identified as a General Pathway for Colloidal Semiconductor Magic-Size Clusters.

Little is known about the formation pathway of colloidal semiconductor magic-size clusters (MSCs). Here, the synthesis of the first single-ensemble ZnSe MSCs, which exhibit a sharp optical absorption singlet peaking at 299 nm, is reported; their formation is independent of Zn and Se precursors used. It is proposed that the formation of MSCs starts with precursor self-assembly followed by Zn and Se covalent bond formation to result in immediate precursors (IPs) which can transform into the MSCs. It is demonstrated that the IPs in cyclohexane appear transparent in optical absorption, and become visible as MSCs exhibiting one sharp optical absorption peak when a primary amine is added at room temperature. It is shown that when the preparation of the IP is controlled to be within the induction period, which occurs prior to nucleation and growth of conventional quantum dots (QDs), the resulting MSCs can be produced without the complication of the simultaneous coproduction of conventional QDs. The present study reveals the existence of precursor self-assembly which leads to the formation of colloidal semiconductor MSCs and provides insights into a multistep nucleation process in cluster science.

Cu-catalyzed controllable C-H mono-/di-/triarylations of imidazolium salts for ionic functional materials.

Herein the Cu-catalyzed direct C-H mono-, di- and triarylations of imidazolium salts with aryl iodides/bromides are accomplished for the first time. The unprecedented alkenylation and alkynylation are also realized using alkenyl and alkynyl iodides, respectively. Moreover, triarylated imidazolium salts with different substituents can be accessed in a modular and one-pot manner. This protocol provides an efficient tool for the assembly of diverse imidazolium-based ionic functional materials. As applicable examples, an electrochromic bisbenzimidazolium salt 7 and a photochromic triarylimidazolium salt 8 are easily obtained.

Rh/Cu-Catalyzed Cascade [4+2] Vinylic C-H O-Annulation and Ring Contraction of α-Aryl Enones with Alkynes in Air.

An unprecedented Rh-catalyzed ketone-directed vinylic C-H activation/[4+2] O-annulation of α-aryl enones with internal alkynes followed by a Cu-catalyzed ring contraction in air to provide multiaryl-substituted furan derivatives has been developed. The preliminary mechanism study identifies the active pyrylium salt as the key intermediate.

Cascade C-H Annulation of Aldoximes with Alkynes Using O2 as the Sole Oxidant: One-Pot Access to Multisubstituted Protoberberine Skeletons.

A cascade double C-H annulation of aldoximes with alkynes to produce benz[a]acridizinium salts is developed by using a simple catalytic system of [Cp*Rh(OAc)2]2 in the presence of Zn(OTf)2 with oxygen as the sole oxidant. In addition, the challenging C-H annulation of aldoximes with alkynes, especially arylalkynes, to synthesize 1H-isoquinolines is also achieved under slightly modified conditions. This protocol provides an efficient one-pot access to multisubstituted dehydroberberinium skeletons from simple starting materials, which can be easily transformed into berberinium and tetrahydroberberine skeletons by controlled hydrogenation.

Room-Temperature Coupling/Decarboxylation Reaction of α-Oxocarboxylates with α-Bromoketones: Solvent-Controlled Regioselectivity for 1,2- and 1,3-Diketones.

A transition-metal-free and room-temperature coupling/decarboxylation reaction between α-oxocarboxylates and α-bromoketones is reported herein. It represents the first mild and regioselective synthesis of either 1,2- or 1,3-diketones from the same starting materials. Notably, the regioselectivity is simply controlled by solvents. The preliminary experimental data and DFT calculations suggest sequential Darzens-type coupling, alkaline hydrolysis, KOH-promoted oxirane opening and decarboxylation in one pot. This method is efficient for the synthesis of α,ß-epoxy-γ-butyrolactone and curcuminoids.

An air-stable half-sandwich Ru(II) complex as an efficient catalyst for [3+2] annulation of 2-arylcyclo-2-enones with alkynes.

An air-stable half-sandwich ruthenium(II) complex, [Ru(p-cymene)(MeCN)3](SbF6)2, was synthesized and characterized. It exhibited unique catalytic ability in a [3+2] annulation reaction of 2-arylcyclo-2-enones with internal alkynes via C(sp(2))-H/alkene functionalization, which offered a rapid and atom-economical methodology to construct various synthetically challenging spiro carbocyclic indenes bearing a quaternary carbon.