Factors Promoting Alkene Migratory Insertion into Metal-Nitrogen Bond during Hydroamination in Recent Studies

: Migratory insertion is a fundamental organometallic transformation that enables the functionalization of an unsaturated bond. Recent reports on catalytic hydroamination provide evidence that supports an intermolecular migratory insertion pathway featuring alkene insertion into metal-nitrogen (M-N) bonds. This article presents factors influencing the rate of migratory insertion in late-transition metal-catalyzed hydroamination, including steric and electronic effects from ligands, alkenes, and metal centers, along with stabilization from coordinated amine intermediates and ordered transition states.

Recoverable Phospha-Michael Additions Catalyzed by a 4-N,N-Dimethylaminopyridinium Saccharinate Salt or a Fluorous Long-Chained Pyridine: Two Types of Reusable Base Catalysts

Phospha-Michael addition, which is the addition reaction of a phosphorus-based nucleophile to an acceptor-substituted unsaturated bond, certainly represents one of the most versatile and powerful tools for the formation of P-C bonds, since many different electrophiles and P nucleophiles can be combined with each other. This offers the possibility to access many diversely functionalized products. In this work, two kinds of basic pyridine-based organo-catalysts were used to efficiently catalyze phospha-Michael addition reactions, the 4-N,N-dimethylaminopyridinium saccharinate (DMAP·Hsac) salt and a fluorous long-chained pyridine (4-Rf-CH2OCH2-py, where Rf = C11F23). These catalysts have been synthesized and characterized by Lu’s group. The phospha-Michael addition of diisopropyl, dimethyl or triethyl phosphites to α, β-unsaturated malonates in the presence of those catalysts showed very good reactivity with high yield at 80–100 °C in 1–4.5 h with high catalytic recovery and reusability. With regard to significant catalytic recovery, sometimes more than eight cycles were observed for DMAP·Hsac adduct by using non-polar solvents (e.g., ether) to precipitate out the catalyst. In the case of the fluorous long-chained pyridine, the thermomorphic method was used to efficiently recover the catalyst for eight cycles in all the reactions. Thus, the easy separation of the catalysts from the products revealed the outstanding efficacy of our systems. To our knowledge, these are good examples of the application of recoverable organo-catalysts to the DMAP·Hsac adduct by using non-polar solvent and a fluorous long-chained pyridine under the thermomorphic mode in phospha-Michael addition reactions.

High Performance Aromatic Polyethersulfones

The modified aromatic polyethersulfones are synthesized. It is shown that the property of the obtained polymers depends on the ratio of the starting monomers. The presence in the initial monomer of two chlorine atoms in combination with an unsaturated bond provides the polyethersulfones based on it with high fire resistance and good physical and chemical properties, including frost resistance.

Evidence for Free Rotation Restriction of Unsaturated Bond in Aggregation-Induced Emission

We experimentally demonstrate that that nonradiative process, which competes with radiative decay, involves two main stages, namely the restricted intramolecular rotation and internal conversion process. The free rotation restriction of the unsaturated bond at the excited state is the key factor for AIE effects.

Ultrafast excited state decay of natural UV filters: from intermolecular hydrogen bonds to a conical intersection

An unsaturated bond in the side chain leads to the ultrafast decay of the excited statesviaa conical intersection independent of solvent properties.