The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon–carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita–Baylis–Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material—nucleophiles, dinucleophiles, electrophiles, and electrophile–nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon–carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon–carbon multiple bond–containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide–generating reactions.

Intrinsic self-healing soft materials such as hydrogels are especially promising for a variety of medical applications. Multistep preparation of starting functional polymer precursors and the expensive stock materials such as tetra-polyethylene glycol are one of the factors that limit the wider use of self-healing hydrogels. Herein, we reported a facile one-pot approach to prepare PEG based self-healing hydrogels from inexpensive commercially available components: polyethylene glycol diacrylate and dithiothreitol. For the first time, borax was used as the catalyst for a thiol−ene Michael-type polyaddition of PEG gels. Borax as the catalyst is quite efficient, allowing rapid gelation (from 40 s to 2 min) under ambient conditions and at room temperature. Essentially, as one catalyst, borax induces the formation of two classes of bonds, covalent thioether and transient boronate ester bonds, were formed at the same time. The storage modulus of the afforded PEG gel (87.5% water) reached up to 10 4 Pa, making the mechanical performance comparable with permanently cross-linked PEG gels. Additionally, the dynamic nature of the boronate ester linkages imparts the gel with self-healing properties, and the obtained gels can be healed within 30 min without external stimulus. Further, the transparent hydrogel is pH and thermal responsive. We believe that the manifold impacts of borax can open a new route to prepare hydrogels with intriguing properties, which find potential application as gel sealant, biosensors, or regenerative medicines. P olymer hydrogels are soft and wet materials, composed of a hydrophilic polymer network structure and large amount of water (50−90%) inside the three-dimensional network. 1 Hydrogels are well-suited for biomedical applications, as they are homogeneous soft materials with hydrophilic nature, porous structure, and tailored stiffness. 2,3 They have shown promising application in a number of fields, including regenerative medicines and biomedical devices, such as biosensors, as well as separation systems. 4−6 Stimuli-responsive (SR) hydrogels have gained considerable attention, which is attributed to the manifold applications they can be used for. SR hydrogels are able to shrink or expand, to switch between solution and gel state or to change their viscosity property in response to the environmental triggers like pH, temperature, 7 or light. 1,8,9 Intensive studies have focused on boronate ester cross-linked hydrogels and constitutional dynamic polymers 10−12 because of the transient nature of the complexation between boronic acids and 1,2-or 1,3-diols, enabling the hydrogel to repair damage autonomously. 13−15 In addition to that, the formation of boronate ester cross-links is a chemical equilibrium process, which can be influenced by both temperature and pH, imparting the hydrogels consequently with thermo-and pHresponsive behaviors. 16,17 Moreover, saccharides like fructose and glucose can form stronger complexes with boric acid, endowing the hydrogels with a glucose responsive function, whi...

Continuous monitoring of catalyzed reactions using infrared spectroscopy (IR) measures the transformation of reactant into product, whereas mass spectrometry delineates the dynamics of the catalytically relevant species present at much lower concentrations, a holistic approach that provides mechanistic insight into the reaction components whose abundance spans 5 orders of magnitude. Probing reactions to this depth reveals entities that include precatalysts, resting states, intermediates, and also catalyst impurities and decomposition products. Simple temporal profiles that arise from this analysis aid discrimination between the different types of species, and a hydroacylation reaction catalyzed by a cationic rhodium complex is studied in detail to provide a test case for the utility of this methodology.

A formal [5 + 3] cycloaddition of zwitterionic allylpalladium intermediates with 1,3-dipoles is developed, providing N,O-containing eight-membered heterocyclic compounds in high yields. Catalytically generated zwitterionic allylpalladium intermediates in situ from vinylethylene carbonates or vinyloxiranes acted as dipolarophile.

A palladium-catalyzed enantioselective [4 + 2] cycloaddition reaction of vinyl benzoxazinones with sulfamate-derived cyclic imines is described, affording the tetrahydroquinazolines bearing several functional rings in high yields (up to 99% yield) with good to excellent diastereoselectivities and excellent enantioselectivities (up to 96% ee). This reaction represents the first Pd-catalyzed asymmetric decarboxylative cycloaddition of vinyl benzoxazinones with imines.