Halogen bonding, parallel to hydrogen bonding, was introduced into the catalytic cycloaddition of carbon dioxide into epoxide (CCE) reactions. A series of halogen‐bond donor (XBD) catalysts of N‐iodopyridinium halide featured with N−I bond were synthesized and evaluated in CCE reactions. The optimal XBD catalyst, 4‐(dimethylamino)‐N‐iodopyridinium bromide ([DMAPI]Br), under screened conditions at 100 °C, ambient pressure, and 1 mol % catalyst loading, realized 93 % conversion of styrene oxide into cyclic carbonate in 6 h. The substrate scope was successfully extended with excellent yields (mostly ≥93 %) and quantitative selectivity (more than 99 %). 1H NMR spectroscopy of the catalyst [DMAPI]Br on substrate epoxide certified that the N−I bond directly coordinated with the epoxide oxygen. A plausible mechanism of halogen‐bonding catalysis was proposed, in which the DMAPI cation functioned as halogen‐bond donor to activate the epoxide, and the counter anion bromide attacked the methylene carbon to initiate the ring‐opening of the epoxide. CCE reactions promoted by N‐iodopyridinium halide, exemplify a first case of halogen‐bonding catalysis in epoxide activation and CO2 transformation.

Here, we report an unprecedented regioselective, intermolecular 1,2-cyanoalkylacylation of feedstock alkenes with readily available oxime esters and aldehydes by N-heterocyclic carbene (NHC) organocatalysis. The crux of this success is the exquisite control over the radical relay process by an NHC organocatalyst. This protocol offers a general platform for diversity-oriented synthesis of valuable ketonitriles under mild, transition-metal-free, and redox-neutral conditions and highlights its potential in the late-stage functionalization of pharmaceutical architectures and natural products.

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The cycloadditions of carbon dioxide into epoxides to afford cyclic carbonates by H-bond donor (HBD) and onium halide (X) cocatalysis have emerged as a key strategy for CO 2 fixation. However, if the HBD is also a halide receptor, the two will quench each other, decreasing the catalytic activity. Here, we propose a strained ion pair tris(alkylamino)cyclopropenium halide (TAC•X), in which TAC repels X. TAC possesses a positively charged cyclopropenium core that makes the vicinal C−H or N−H a nonclassical HBD. The interionic strain within TAC•X makes TAC a more electrophilic HBD, allowing it to activate the oxygen of the epoxide and making X more nucleophilic and better able to attack the methylene carbon of the epoxide. NMR titration spectra and computational studies were employed to probe the mechanism of the cycloaddition of CO 2 to epoxides reactions under the catalysis of TAC•X. The 1 H and 13 C{ 1 H}NMR titration spectra of the catalyst with the epoxide substrate unambiguously confirmed H-bonding between TAC and the epoxide. DFT computational studies identified the transition states in the ring-opening of the epoxide (TS1) and in the ring-closure of the cyclic carbonate (TS2).

C-H activation | C-N activation | Homogeneous catalysis | Cobalt catalysis | Allylation[Cp*Co(CO)I 2 ] effectively catalyzes pyridyl-directed C-H allylation of arenes with allylic amines in the presence of AgOAc and CF 3 COOAg. The reaction features ortho-position monoallylation of 2-pyridylarenes, giving the allylated arenes in moderate to high yields. A range of functional groups including OMe, Me, Ph, F, Cl, Br, CF 3 , C(O)Me, COOEt, and COOH groups are tolerated. Pyrimidyl-directed C-H allylation of arenes were also performed under the same conditions. Reaction of 2-phenylpyrimidine, 2-(4-methoxyphenyl)pyrimidine, and 2-(3-fluorophenyl)pyrimidine leads to a mixture of ortho-position mono-and bisallylation products. Reaction of other 2-(substituted aryl)pyrimidines resulted in ortho-position monoallylation products.