The first Ni-promoted prototype reaction based on the tandem C-H activation of heteroarenes with alkene isomerization is demonstrated, leading to the branched hydroheteroarylation products. Simultaneously, the reaction selectivity can be chemically switched to linear adducts through Ni-Al tandem catalysis.

Treatment of [HC{(MES)N(CHCH)N(CH 2 CH 2 NHtBu}]Br • HBr (1) with an excess of NaOH afforded the organic-soluble imidazolium salt 2, [HC{(MES)N(CHCH)N(CH 2 CH 2 NHtBu}]Br, the structure of which was confirmed by X-ray crystallography. Deprotonation of 2 by NaN(SiMe 3 ) 2 yielded the thermally unstable amino-linked free carbene, 3. The molecular structure of 3 was determined by single-crystal X-ray analysis, revealing an unexpectedly close intermolecular contact associated with the carbene and amine through an N-H • • • C interaction. In contrast to compound 3, the reaction of 2 with LiN(SiMe 3 ) 2 gave the much more stable LiBr carbene adduct 3-LiBr, which serves as an effective carbene transfer agent for organoaluminum compounds to give the corresponding AlR 3 -NHC (4a, Me; 4b, Et) in high yield. X-ray diffraction studies of 4a and 4b confirmed the formation of monomeric distorted tetrahedral Al species, in which the NHC binds via conventional σ-donation of the lone pair to the electrophilic metal center. The reaction of benzaldehyde with 4a resulted in the quantitative formation of a zwitterionic species consisting of a distorted pseudotetrahedral aluminate center covalently linked to imidazolium, 5. The product 5 resulted from insertion of the carbonyl moiety into the Al-carbene group. A similar reactivity with benzaldehyde was observed in compound 6, which was independently synthesized from addition of 1,3-bis(mesityl)imidazol-2-ylidene to AlMe 3 .

Abscisic acid (ABA) is a key regulator of plant responses to abiotic stresses, such as drought. Abscisic acid receptors and coreceptors perceive ABA to activate Snf1‐related protein kinase2s (SnRK2s) that phosphorylate downstream effectors, thereby activating ABA signaling and the stress response. As stress responses come with fitness penalties for plants, it is crucial to tightly control SnRK2 kinase activity to restrict ABA signaling. However, how SnRK2 kinases are inactivated remains elusive. Here, we show that NUCLEAR PORE ANCHOR (NUA), a nuclear pore complex (NPC) component, negatively regulates ABA‐mediated inhibition of seed germination and post‐germination growth, and drought tolerance in Arabidopsis thaliana. The role of NUA in response to ABA depends on SnRK2.2 and SnRK2.3 for seed germination and on SnRK2.6 for drought. NUA does not directly inhibit the phosphorylation of these SnRK2s or affects their abundance. However, the NUA‐interacting protein EARLY IN SHORT DAYS 4 (ESD4), a SUMO protease, negatively regulates ABA signaling by directly interacting with and inhibiting SnRK2 phosphorylation and protein levels. More importantly, we demonstrated that SnRK2.6 can be SUMOylated in vitro, and ESD4 inhibits its SUMOylation. Taken together, we identified NUA and ESD4 as SnRK2 kinase inhibitors that block SnRK2 activity, and reveal a mechanism whereby NUA and ESD4 negatively regulate plant responses to ABA and drought stress possibly through SUMOylation‐dependent regulation of SnRK2s.

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