Synergistic Hydrocobaltation and Borylcobaltation Enable Regioselective Migratory Triborylation of Unactivated Alkenes.

The structural diversity of sp3 -triorganometallic reagents enhances their potentiality in the modular construction of molecular complexity in chemical synthesis. Despite significant achievements on the preparation of sp3 1,1,1- and 1,1,2-triorganometallic B,B,B-reagents, catalytic approaches that enable the installation of multiple boryl groups at skipped carbons of unactivated alkenes still remain elusive. Herein, we report a cobalt-catalyzed selective triborylation reaction of unactivated alkenes to access synthetically versatile 1,1,3-triborylalkanes. This triborylation protocol provides a general platform for regioselective trifunctionalization of unactivated alkenes, and its utility is highlighted by the synthesis of various value-added chemicals from readily accessible unactivated alkenes. Mechanistic studies, including deuterium-labelling experiments and evaluation of potential reactive intermediates, provide insight into the experimentally observed chemo- and regioselectivity.

Chromium-Catalyzed Selective Dimerization/Hydroboration of Allenes to Access Boryl-Functionalized Skipped (E,Z)-Dienes.

A chromium-catalyzed dimerization/hydroboration of allenes is developed to access synthetically versatile boryl-functionalized skipped dienes with a catalyst generated in situ from CrCl2 and a pyridine-2,6-diimine ligand mes PDI. A variety of allenes reacted with pinacolborane (HBpin) to afford the corresponding boryl-functionalized (E,Z)-1,4-dienes in high yields and with excellent selectivity. Electron paramagnetic resonance (EPR) spectroscopic studies suggest that this chromium-catalyzed reaction probably proceeds through a chromium(I) hydride intermediate.

Two-Fold C-H/C-H Cross-Coupling Using RhCl3·3H2O as the Catalyst: Direct Fusion of N-(Hetero)arylimidazolium Salts and (Hetero)arenes.

[Cp*RhCl2]2 is the most prevailing catalyst employed for rhodium-catalyzed chelation-assisted C-H/C-H cross-coupling reactions due to the special ligand effect of Cp*. In this article, a novel concept of using a simple inorganic rhodium salt, RhCl3·3H2O, as the catalyst by taking advantage of in situ π-coordination to Rh with a (hetero)aromatic reaction component to stabilize Rh intermediates is proposed and evaluated. Our studies not only prove the feasibility of this concept but also disclose a novel 2-fold C-H/C-H cross-coupling reaction of N-(hetero)arylimidazolium salts with various (hetero)arenes to access water-soluble, fluorescent, cationic, and planar polycyclic heteroaromatic molecules, in which RhCl3·3H2O outperforms [Cp*RhCl2]2. Mechanistic experiments and DFT calculations reveal that this successive quadruple C-H activation reaction consists of two different C-H activation modes, i.e., concerted metalation-deprotonation (CMD) and oxidative addition. Notably, this is the first report of a C-H bond activation via oxidative addition to RhI in a bi(hetero)aryl formation with hydrogen evolution. Finally, the different ligand electrochemical parameters of neutral (hetero)arenes and anionic Cp* are used to explain the different catalytic behaviors of RhCl3·3H2O and [Cp*RhCl2]2.

Tandem Rh-Catalyzed [4 + 2] Vinylic C-H O-Annulation of Exocyclic Enones with Alkynes and 1,5-H Shift.

Active pyrylium intermediates are in situ generated by a Rh-catalyzed vinylic C-H annulation reaction between exocyclic α,ß-enones and alkynes, which undergo a base-promoted rearrangement via 1,5-H shift to form 1H-benzo[f]chromene derivatives.

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.

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.

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.

Transition-metal-free formal decarboxylative coupling of α-oxocarboxylates with α-bromoketones under neutral conditions: a simple access to 1,3-diketones.

A transition-metal-free formal decarboxylative coupling reaction between α-oxocarboxylates and α-bromoketones to synthesize 1,3-diketone derivatives is presented. In this reaction, a broad scope of substrates can be employed, and neither a metal-based reagent nor an additional base is required. DFT calculations reveal that this reaction proceeds through a coupling followed by decarboxylation mechanism and the α-bromoketone unprecedentedly serves as a nucleophile under neutral conditions. The rate-determining step is an unusual hydrogen-bond-assisted enolate formation by thermolysis.

Highly selective fluorescent recognition of sulfate in water by two rigid tetrakisimidazolium macrocycles with peripheral chains.

The reinforced molecular recognition of two rigid tetrakisimidazolium macrocycles resulted in highly selective fluorescent recognition of sulfate dianion in water with an unprecedentedly high association constant of 8.6 × 10(9) M(-2). Besides the electrostatic interaction, the single crystal X-ray analysis revealed that sulfate was encapsulated in a pseudohexahedral cavity of a sandwich structure by two orthogonally packed macrocycles via eight hydrogen bonds between the C2 hydrogen atoms of the imidazolium units and the oxygen atoms of sulfate. This sandwich structure was reinforced by the π-π stacking between the phenyl and the triazinonide rings and multiple charge-assisted hydrogen bonds between the peripheral chains and the rigid backbones. Notably, these peripheral-backbone hydrogen bonds rendered the flexible peripheral chains to coil around the sandwich structure to shield sulfate inaccessible to water. This binding process was visible by fluorescence enhancement, which was attributed to a restrained rotation and better conjugation of the macrocycle backbone upon binding to sulfate.

Novel bisimidazolium pincers as low loading ligands for in situ palladium-catalyzed Suzuki-Miyaura reaction in the ambient atmosphere.

A series of novel triazinonide-bridged bisimidazolium pincers were easily synthesized by quaternization of functionalized N-phenylimidazoles with highly reactive cyanuric chloride under mild conditions. The pincer was proven to be a very efficient ligand for in situ Pd-catalyzed Suzuki-Miyaura reaction with ppm-level catalyst loading.

Elements of regiocontrol in the direct heteroarylation of indoles/pyrroles: synthesis of bi- and fused polycyclic heteroarenes by twofold or tandem fourfold C-H activation.

Cross-coupling: the "chelation-directed control" and "catalytic-system-based control" strategies effectively switch the C2/C3-site selectivity in the heteroarylation of indoles and pyrroles with N-heteroarenes by a palladium-catalyzed twofold C-H activation to form biheteroarenes and are further extended to the synthesis of complex fused tri- and tetracyclic heteroarenes by a tandem fourfold C-H activation.

[Effect of interlocking intramedullary nail in treatment of open tibial and fibula fractures].

OBJECTIVE: To determine the effect of interlocking intramedullary nail in treatment of open tibial and fibula fractures and analyze the method to promote the bone union. METHODS: From December 2003 to June 2006, thirty-five patients with open tibial and fibula fracture were treated with emergency debridement, interlocked intramedullary fixation for tibia and fixed fibula at the same time. During operation, the bone marrow was collected and grafted into the fracture gaps. Among them, there were 27 males and 8 females, involving in 22 left legs and 13 right legs. Their ages ranged from 19 to 65 years, with an average of 34.7 years. The location of fracture was the middle of the tibia and fibula in 16 cases, the distal 1/3 of the tibia and fibula in 12 cases and the proximal 1/3 in 7 cases. According to the Gustilo classification of open injuries, there were 7 cases of type I, 19 cases of type II, 8 cases of type III a and 1 case of type III b. The mean range of knee motion was 48.3 degrees (45-70 degrees). The mean time from injury to operation was 4.3 hours (50 minutes to 7 hours). RESULTS: The mean operation time was 94 minutes (60-132 minutes) and the mean blood loss was 122 mL (100-350 mL). The wound healed by first intention in 32 patients. Incision was sutured in 2 cases of type III a fractures after operation 4 days, gastrocnemius flap graft was performed in 1 case of type III b fracture 1 week after operation. They all achieve good healing. No fractures split off, no iatrogenic nerve and vascular injury occurred, no osteofascial compartment syndromes or deep vein thrombus happened. Tension blisters appeared in 1 case of type II fracture after operation and subsided after 5 days. Patients were followed up for 14-43 months (mean 22 months). The X-ray films showed that fracture union was observe in 30 cases after 14 weeks of operation, in 3 cases after 18 weeks and in 1 case after 22 weeks of operation. The fractures union time was 15.2 weeks on average. About 2 cm nonunion in lateral tibial appeared in 1 case of type I fracture. No fracture occurred again. The mean range of knee motion was 127 degrees (121-135 degrees). The mean HSS score was 96.5 (87-100) at the end of the follow-up. The excellent and good rate was 100%. CONCLUSION: The curative effect of interlocking intramedullary nail is definite in treatment of open tibial and fibula fractures and it can enhance fracture union to plant bone marrow into the fracture gaps.