An effective Pd(0) carbene complex was successfully employed in the decarboxylative coupling of the heteroaromatic carboxylic acids (imidazo[1,2-a]pyridine and isoxazole) with aryl halides. For carboxyindoles, either decarboxylative coupling or tandem C-H arylation and decarboxylation occurred, leading to the formation of C2-monoarylated indoles.

A palladium(0) NHC complex Pd0(LH1)2(MA) (MA = maleic anhydride) was prepared from the amide-imidazolium salt [LH1H2]Cl (H1 = NH proton; H2 NCHN proton). The X-ray diffraction studies confirmed that a η2-MA ligand and two monodentate NHC ligands with the H1 protons remaining intact are coordinated. These NH protons are involved in intra- or intermolecular hydrogen bonds stabilizing the solid-state structure. Degradation of Pd(LH1)2(MA) in air leads to the formation of the chelate complex trans-PdIIL2 and other unidentified products. Negative-ion electrospray mass spectrometry revealed some intriguing Pd(0) species, including a 14-electron [Pd0L]− species that bears only a bidentate NHC/amido ligand. The anionic amido group imparts a high electron density on a palladium center, as shown by X-ray photoelectron study. The palladium(0) precatalyst is highly efficient in catalyzing Heck reactions with activated aryl chlorides in ionic liquid. For deactivating aryl chlorides and bulky aryl bromides, cis-PdIIL2 is more effective. A range of Heck-coupled products can be prepared by Pd0(LH1)2(MA) and cis-PdIIL2. The latter complex also successfully mediates one-pot sequential Heck/Heck and Suzuki/Heck coupling reactions with 4-bromochlorobenzene as substrate.

Based on the ligand scaffold of an imidazolyl/benziimidazolyl moiety and a N‐CH2C(=O)NHPh substituent, two series of ligand precursors with ortho hydroxy groups incorporated on the N‐phenyl rings were prepared. The structural fine tuning of the ligand scaffold allowed the synthesis of tetranuclear palladium complexes with abnormal N‐heterocyclic carbene (aNHC) ligands. For precursors with C2‐methyl blocking groups, pyridine‐assisted C−H bond activation led to the formation of mononuclear tridentate palladium aNHC complexes or tetranuclear complexes with tridentate CNO donors. Representative mononuclear and tetranuclearpalladium aNHC complexes were structurally characterized by X‐ray diffraction studies, revealing very short Pd−C bond distances. The tetranuclear palladium aNHC complexes were very effective in catalyzing Mizoroki‐Heck coupling reaction, and were capable of employing a range of aryl chlorides including deactivated substrates with low palladium loading of 0.2 mol%.magnified image

The ligand combination of semirigid 2,6-bis(imidazole-1-yl)pyridine (2,6-bip) and rigid benzenecarboxylate allow the isolation of three new zinc coordination polymers. Hydrothermal synthesis between Zn(NO3)2·6H2O, 2,6-bip, and terephthalic acid under basic condition affords [Zn(1,4-bdc)(2,6-bip)·2H2O] n (1) (1,4-bdc =1,4-benzenedicarboxylate), which shows an undulating 2D (4,4)-network with 2-fold interpenetration. Contrastingly, solvothermal synthesis with identical starting materials in DMF, yields [Zn(1,4-bdc)(2,6-bip)·DMF] n (2), which exhibits noninterpenetrating 2D (4,4)-network. Thus 1 and 2 are pseudo-supramolecular isomeric pair, illustrating the strong effect of guest solvents in controlling the entanglement. A similar hydrothermal reaction to 1 but using 1,3,5-benzenetricarboxylic acid instead yields [Zn2(μ−OH)(1,3,5-btc)(2,6-bip)·H2O]n (3) (btc = benzenetricarboxylate), which exhibits a (3,4,6)-connected 3D framework with an unprecedented {5.6.7}2{52.6.7.82}2{54.62.73.84.92} topology. Compound 1 and 2 show reversible solvent incorporation properties.

Scheme 1 Coordination modes of 2-stp in 1 and 2.

The synthesis of biaryls from unactivated arenes and a broad range of aryl bromides and chlorides via the direct C À H functionalization can be efficiently performed with the aid of amido-functionalized imidazolium salts as organocatalysts. This method avoids the use of toxic transition metal catalysts and organometallic reagents.

Long-term memory (LTM) formation depends on the conversed cAMP response elementbinding protein (CREB)-dependent gene transcription followed by de novo protein synthesis. Thirsty fruit flies can be trained to associate an odor with water reward to form waterreward LTM (wLTM), which can last for over 24 hours without a significant decline. The role of de novo protein synthesis and CREB-regulated gene expression changes in neural circuits that contribute to wLTM remains unclear. Here, we show that acute inhibition of protein synthesis in the mushroom body (MB) αβ or γ neurons during memory formation using a cold-sensitive ribosome-inactivating toxin disrupts wLTM. Furthermore, adult stage-specific expression of dCREB2b in αβ or γ neurons also disrupts wLTM. The MB αβ and γ neurons can be further classified into five different neuronal subsets including αβ core, αβ surface, αβ posterior, γ main, and γ dorsal. We observed that the neurotransmission from αβ surface and γ dorsal neuron subsets is required for wLTM retrieval, whereas the αβ core, αβ posterior, and γ main are dispensable. Adult stage-specific expression of dCREB2b in αβ surface and γ dorsal neurons inhibits wLTM formation. In vivo calcium imaging revealed that αβ surface and γ dorsal neurons form wLTM traces with different dynamic properties, and these memory traces are abolished by dCREB2b expression. Our results suggest that a small population of neurons within the MB circuits support long-term storage of water-reward memory in Drosophila.

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